ACID-BASE TITRATIONS Introduction

ACID-BASE TITRATIONSIntroduction

The complete applications package

At Radiometer Analytical, we put applications first. When you order one of our new genera-tion of titration workstations with a dedicated application package, you have everything youneed to get started right away: electrodes, specific accessories, standards, maintenancesolutions and, of course, methods and application notes.

Application booklets

Whether in aqueous or non-aqueous media, acid-basetitrations are the most frequently performed titrations inanalytical laboratories in all fields. Instructions for perform-ing some of the most commonly used applications aregiven in this booklet together with calibration proceduresfor the corresponding titrants and electrodes. Certainmodifications may be needed to take into account specificregulations or standards in force in certain countries, inparticular regarding results presentation.

Radiometer Analytical produces other technique-based applications booklets as well as arange of applications dedicated to particular sectors. Ask your local representative for thefollowing booklets:

Technique Part No.

Precipitation titrations D41T010Complexometric titrations D41T011Redox titrations D41T012

Dedicated Part No.

Food and beverage analysis D41T004Plating bath analysis D41T005Water and environmental analysis D41T006Chemical industries D41T007

Our Applications Laboratory is continually developing new applications.

For the latest updates visit us at www.titration.com.

TTEP01.09MIN ................. Operational Qualification (End Point Titration Manager)

TTIP01.01MIN ................... Operational Qualification (Inflection Point Titration Manager)

TTEP01.01MIN ................. Calibration of an Acidic Solution

TTEP01.02MIN ................. Calibration of an Alkaline Solution

TTEP01.05MIN ................. Alkalinity of Bleach

TTEP01.01ENV................. Alkalinity of Water

TTEP01.01AFD ................. Titratable Acidity in Wines or Juices

TTEP01.02AFD ................. Acidity of Milk

TTEP01.03AFD ................. Acidity of Mustard and Associated Products

TTEP01.05AFD ................. Acidity of Cheese

TTEP01.06AFD ................. Total Titratable Acidity in Vinegar

TTEP01.08AFD ................. Acidity and HCHO Number in Fruit Juices

TTEP01.01PLA ................. Analysis of a Finishing bath

TTEP01.03PLA ................. Total and Free Alkalinity of a Cleaning Bath

TTEP01.04PLA ................. NaOH and HCHO in Electroless Copper Bath

TTEP01.05PLA ................. NaOH in Electroless Copper Bath

TTEP01.06PLA ................. Boric Acid in Plating Baths

TTEP01.07PLA ................. Boric Acid and Nickel Content

TTEP01.01PHR ................ Gastric Acidity

TTEP01.01PET ................. Acid Number of Petroleum Products (End Point Titration Manager)

TTIP01.01PET .................. Acid Number of Petroleum Products (Inflection Point Titration Manager)

TTIP01.02AFD .................. Acidity of Edible Oils

TTEP01.09AFD ................. Carbon Dioxide in Wines

TTIP02.01PET .................. TBN according to ISO 3771/D2896

ACID-BASE TITRATIONS

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End Point Titration ManagerOperational Qualification

Introduction

The operational qualification pro-cedure demonstrates that an in-strument runs according to theoperational specifications in theselected environment. For an endpoint titration manager, this opera-tion can consist of two steps:- Calibration and checking of a pHmeasurement electrode system- Titration of anhydrous sodiumcarbonate standard using a com-mercial standard solution of HCl.

Principle

The reaction has 2 steps

Na2CO

3 + HCl � NaHCO

3 + NaCl

NaHCO3 + HCl � CO2 + H2O + NaCl

corresponding to 2 different endpoints.The operational qualification takesinto account the second equiva-lence point (pH 3.90) correspond-ing to the complete neutralisationof sodium carbonate.

Electrode and reagents

pHC2011-8 Combined pH Elec-trode (part no. E16M317)

T201 Temperature Sensor (partno. E51M001)

IUPAC Series pH standardspH 4.005 (part no. S11M002),pH 7.000 (part no. S11M004) andpH 10.012 (part no. S11M007)

100 g bottle of Merck "certified"sodium carbonate (part no.1.06394.0100) or 500 g bottle of"pro analysis" Merck sodium car-bonate (part no. 1.06392.0500)

1 l of "ready to use" Merck HCl0.1 mol/l (part no. 1.09060.1000)

Distilled water

End Point titration settings

ElectrodepH: pHC2011-8Calibration request: YESNumber of cycles: 2Number of buffers: 3Measurement: StirringTemperature: probe

Calibration parametersStability: 15 mpH/minAcceptation time: 2.00 minMax. stab. Time: 5.00 minAcceptation criteria: YESIso. pH: 6.65 pH

Calibration solutions1: 4.005 (IUPAC)2: 7.000 (IUPAC)3: 10.012 (IUPAC)Min. zero pH: 5.8 pHMax. zero pH: 7.5 pHMin. sensitivity: 95%Max. sensitivity: 103%

TitrantID: HClUnit: MTitre: Entered

MethodPredose: see belowStart timer: 45 secMax. volume: see belowNumber of EP: 1Min. speed: 0.2 ml/minMax. speed: 5.00 ml/minDirection: decreasing pHEnd point: 3.90 pHDelay: 10 secProportional band: 3.00 pH

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ResultsSample unit: mgNumber of result: 1Acceptation criteria: YESResult unit: %Molar weight: 105.99Reaction: 1 smp + 2 titrMinimum value: 99Maximum value: 101

Procedure

Electrode calibration andcheckingIf the electrode is new, condition itby immersion in distilled water forat least 1 hour

Connect the pHC2011-8 combinedpH electrode and the T201 Tem-perature Sensor

Using the above-mentioned set-tings, RUN an electrode calibra-tion with 2 or more cycles

At the end of the last cycle, cali-bration results should be accepted

Ensure that the temperature of thestandards does not differ by morethan 2°C.

End point titration operationqualificationFit the titration manager with HCl0.1 M as titrant and install thetitrant.

Preparation of Na2CO3As indicated, dry approximately 5 gof anhydrous sodium carbonate inan oven for 4 hours at 250°C. Letit cool to room temperature in adesiccator with P2O5

or anotherhumidity adsorber.

End point titrationTo determine the necessaryamount of sodium carbonate

With a 25 ml burette capacityWeigh exactly 85-90 mg ofNa

2CO

3

This weight corresponds to1.6-1.8 meq or 16-18 ml of HCl0.1M. Use a predose correspond-ing to 10 ml and a maximum vol-ume of 25 ml

With a 10 ml burette capacityUse the same settings as the25 ml burette capacity

With a 5 ml burette capacityWeigh exactly 40-45 mg ofNa

2CO

3

Use a maximum volume of 10 ml

No predose.

Dissolve the weighed sodium car-bonate quantitatively in the titra-tion beaker with 50 to 80 ml offreshly distilled water.

Immerse the electrode and thedelivery tip in the solution.

Using the above-mentioned set-tings, run a titration with 3 differentsamples. Results should be ac-cepted between 99 and 101%.

End Point Titration Manager Operational Qualification

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Inflection Point Titration ManagerOperational Qualification

Introduction

The operational qualification pro-cedure demonstrates that an in-strument runs according to theoperational specifications in theselected environment. For a titra-tion manager using automaticinflection point determination, thisoperation can consist of two steps:

- Calibration and checking of a pHmeasurement electrode system,

- Titration of anhydrous sodiumcarbonate standard using a com-mercial standard solution of HCl.

Principle

The reaction has 2 steps corre-sponding to 2 different inflectionpoints:

Na2CO

3 + HCl � NaHCO

3 + NaCl

NaHCO3 + HCl � CO

2 + H

2O + NaCl

The operational qualification takesinto account the second equiva-lence point (close to pH 4.00)

corresponding to the completeneutralisation of sodium carbonate.

The Titration Manager settingsallow the complete titration curveto be seen.



T201 Temperature Sensor (partno. E51M001)

IUPAC Series pH standards

pH 4.005 (part no. S11M002)

pH 7.000 (part no. S11M004)

pH 10.012 (part no. S11M007)

100 g bottle of Merck "certified"sodium carbonate (part no.1.06394.0100) or 500 g bottle of"pro analysis" Merck sodium car-bonate (part no. 1.06392.0500)

1 l of "ready to use" Merck HCl0.1 mol/l (part no. 1.09060.1000)

Distilled water

Continuous IP titrationsettings

ElectrodepH: pHC2011-8Calibration request: YESNumber of cycles: 2Number of buffers: 3Measurement: StirringTemperature: probe

Calibration parametersStability: 15 mpH/minAcceptation time: 2.00 minMax. stab. Time: 5.00 minAcceptation criteria: YESIso. pH: 6.65 pH

Calibration solutions1: 4.005 (IUPAC)2: 7.000 (IUPAC)3: 10.012 (IUPAC)Min. zero pH: 5.8 pHMax. zero pH: 7.5 pHMin. sensitivity: 95%Max. sensitivity: 103%

TitrantID: HClUnit: MTitre: Entered

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MethodStirring speed: 550 rpm

Predose: 0 mlStart timer: 45 secMax. volume: (see notes)Stop point: 2.000 pHSmoothing parameter: 8Number of IP: 2Min. speed: 0.2 ml/minMax. speed: 5.00 ml/minDirection: decreasing pH

Inflection 1Min. ordinate: 7.00 pHMax. ordinate: 10.00 pHInflection 2Min. ordinate: 2.80 pHMax. ordinate: 6.00 pH

Sample unit: mgSample amount: (see notes)

ResultsResults by: cumulateNumber of result: 1Acceptation criteria: YES

Result 1Result unit: %Molar weight: 105.99Reaction: 1 smp + 2 titrCalculate with IP: 2Minimum value: 99Maximum value: 101

Procedure

Electrode calibration andcheckingIf the electrode is new, condition itby immersion in distilled water forat least 1 hour.Connect the pHC2011-8 electrodeand the T201 Temperature SensorUsing the above-mentioned set-tings, RUN an electrode calibra-tion with 2 or more cycles.At the end of the last cycle, cali-bration results should be acceptedEnsure that the temperature of thestandards does not differ by morethan 2°C.

Operation qualification in con-tinuous IPFit the burette of the titration man-ager with HCl 0.1 M as titrant andinstall the titrant

Preparation of Na2CO3As indicated, dry approximately5 g of anhydrous sodium carbon-ate in an oven for 4 hours at250°C. Let it cool to room tem-perature in a desiccator with P2O5or another humidity adsorber.

Notes

To determine the necessaryamount of sodium carbonate

With a 25 ml burette capacity

Weigh exactly approximately85-90 mg of Na

2CO

3

This weight corresponds to

1.6-1.8 meq or 16-18 ml of HCl0.1M. Use a maximum volumeclose to 20/22 ml

With a 10 ml burette capacity

Weigh exactly approximately 40 mgof Na

2CO

3. Use a maximum vol-

ume of 10 ml

With a 5 ml burette capacityWeigh exactly approximately 20 mgof Na

2CO

3. Use a maximum vol-

ume of 5 ml

Dissolve the weighed sodium car-bonate quantitatively in the titra-tion beaker with 50 to 80 ml offreshly distilled water.

Immerse the electrode and thedelivery tip in the solution.

Using the above-mentioned set-tings, run a titration on 3 differenttests or replicates. Results shouldbe accepted between 99 and 101%.

Inflection Point Titration Manager Operational Qualification

Calculations are programmed togive a result according to the de-livered titrant volume at the inflec-tion point situated in the accept-ance range 2.80-6.00 pH

Dynamic IP Titrationsettings

This application note can be usedwith incremental addition of titrant(Dynamic IP)

Dynamic IPSpeed: 5.00 ml/minDynamic dose: 30Maximum dose: 0.3 mlStability: 100 mpH/minAcceptation: 10 s

These settings were tested with a10 ml burette. The others settingsare unchanged.

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Calibration of an Acidic Solution

Standard preparation

To calibrate acid solution, useanalytical grade Na

2B

4O

7,10 H

2O

as standard (molecular weight381.4 g/mol); it reacts with H+ ionsaccording to

B4O

7- - + 2H+ + H

2O � 4HBO

2

A 0.1 eq/l borax solution contains0.05 mol/l (or 1/20 mol/l) of borax.To prepare 1000 ml of 0.1 eq/l ofstandard, weigh exactly 19.070 gof analytical grade Na

2B

4O

7,10 H

2O

and dilute to 1000 ml with a volu-metric flask.

A 0.1 eq/l solution can be storedfor 1 month.



Freshly distilled water

0.1 eq/l borax standard solution

IUPAC Series pH standardspH 4.005 (part no. S11M002) andpH 10.012 (part no. S11M007)


Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 5.10 pHStirring delay: 10 secondsMinimum speed: 0.2 ml/minMaximum speed: 6.0 ml/minProportional band: 3.0 pHEnd point delay: 5 secondsDirection: Decreasing pHSample unit: mlStandard amount: 20Standard conc.: 0.1 eq/lResult: eq/l

Reagent preparation

In aqueous media, 2 acids are mainly used as titrants: HCl (concentrated commercial solution is around 12M)or H

2SO

4 (18M or 36N). It is also possible to use HNO

3 (concentrated commercial solution is nearly 12.8M).

To prepare 1000 ml of 0.1 eq/l strong acid solution, dilute X ml of concentrated acid (see table) in 200 ml ofdistilled water and, by means of a volumetric flask, dilute to 1000 ml. CAUTION: These operations are highlyexothermic. Observe laboratory safety regulations.

Acid Conc. % w/w Density g/l Conc. M (mol/l) X = Vol (ml)

HNO3

60% 1.35 12.8 7.8

H2SO

4 96% 1.83 18 2.8

HCl 37% 1.18 12 8.3

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Procedure

Prepare the titration system with a25 ml burette and 0.1 eq/l acidsolution as titrant.

Calibrate the pHC2401-8 electrodeusing IUPAC standards.

Do not forget to fill the reagentbottle absorption chamber withabsorbent.

Pipette exactly 20 ml of borax0.1 eq/l.

Complete to 100 ml with distilledwater.

Dip electrode and delivery tip inthe solution.

Start method by pressing the RUNkey.

Results

The result is expressed as eq/lconcentration and based on thefollowing formula:

Vol(acid sol) * C(acid sol) =Vol(borax sol) * C(borax sol)

The calibration result can beaccepted if 5 determinationsgive a result with a relativestandard deviation of less than0.5%.

Notes

a) Using a solution as standard, itis best to use a standard concen-tration close to the titrant concen-tration. This allows closed volumesfor titrant and standard.

For the best result accuracy, pi-pette a standard volume corres-ponding to a delivered titrant vol-ume greater than 50% of the usedburette cylinder.

b) The application note uses a25 ml cylinder capacity. If you usea 5 or 10 ml cylinder for the bu-rette, pipette 5 ml of standard andmodify the method as follows:

Predose: 2 mlMaximum volume: 8 ml

c) It is possible to calibrate anacid titrant by weighing an amountof borax.With a 25 ml burette cylinder ca-pacity.Exactly weigh approximately 380 mgof borax.

In the STANDARD screen ENTERStandard unit: mgStandard amount: xx.xConcentration unit: %Concentration: 100

(or purity of the standard)Molecular weight: 381.4

And in the RESULT screen ENTERResult: eq/l

For HCl or HNO3 (result in eq/l or

mol/l)Coefficients: 1 Standard + 2 Titrant

For H2SO

4 (result in eq/l)

Coefficients: 2 Standard + 2 Titrant

For H2SO

4 (result in mol/l)

Coefficients: 1 Standard + 1 Titrant

Calibration of an Acidic Solution

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Calibration of an Alkaline(NaOH or KOH) Solution

Reagent preparation

There are several ways to preparefree carbonate NaOH or KOHsolution.To prepare 0.1 eq/l NaOH or KOHsolution the easiest way is to:

Take a new bottle of NaOH orKOH pellets and quickly weigh4.00 g of NaOH or 5.60 g of KOH

(NaOH has a molecular weight of40 g/mol and KOH 56 g/mol)

Using a conical flask, dissolve thepellets in 200 ml of hot (40°Capprox.) freshly boiled distilledwater, cover the flask with plasticfilm and leave to cool to roomtemperature.

Using a volumetric flask, quicklycomplete to 1000 ml with thesame freshly boiled distilled water.

For long storage, use a polytheneflask.

Standard preparation

To calibrate NaOH solution, useoxalic acid H

2C

2O

4, 2H

2O as stand-

ard (molecular weight 126.0 g/mol).As in aqueous media, the 2 acidfunctions are titrated together; a0.1 eq/l oxalic solution contains0.05 mol/l (or 1/20 mol/l) of oxalicacid.

To prepare 1000 ml of 0.1 eq/l ofstandard.Weigh exactly 6.300 g (126.0/20)of oxalic acid. Using a volumetricflask, dissolve to 1000 ml withfreshly boiled distilled water.



Freshly boiled distilled water

0.1 eq/l oxalic acid standard solu-tion



Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.55 pHStirring delay: 10 secondsMinimum speed: 0.2 ml/minMaximum speed: 6.0 ml/minProportional band: 3.0 pHDirection: Increasing pHEnd point delay: 5 secondsSample unit: mlStandard amount: 20Standard conc.: 0.1 eq/lResult: eq/l

Procedure

Prepare the titration system with a25 ml burette and 0.1 eq/l NaOHsolution as titrant.

Calibrate the pHC2401-8 elec-trode using IUPAC standards.

Do not forget to fill the reagentbottle absorption chamber withabsorbent CO

2.

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Pipette exactly 20 ml of oxalicacid 0.1 eq/l.

Complete to 100 ml with distilledwater.



Results

The result is expressed as eq/lconcentration and based on thefollowing formula

Vol(NaOH sol) * C(NaOH sol) =Vol(oxalic acid sol) * C(oxalic acid sol)

The calibration result can beaccepted if 5 determinationsgive a result with a relativestandard deviation of less than0.5%.

Notes

a) Using a solution as standard, itis best to use a standard concen-tration close to the titrant concen-tration. This allows closed vol-umes for titrant and standard.For the best result accuracy, pi-pette a standard volume corre-sponding to a delivered titrantvolume greater than 50% of theused burette cylinder.

b) The application note uses a25 ml cylinder capacity. If you usea 5 or 10 ml cylinder for the bu-rette, pipette 5 ml of standard andmodify the method as follows:

Predose: 2 mlMaximum volume: 8 ml

c) It is possible to calibrate a ba-sic titrant by weighing an amountof oxalic acid.

With a 25 ml burette cylinder ca-pacity

Exactly weigh approximately 120 mgof oxalic acid

In the STANDARD screen ENTERStandard unit: mgStandard amount: xx.xConcentration unit: %Concentration: 100

(or purity of the standard)Molecular weight: 126.0

And in the RESULT screen ENTER

Result: eq/lCoefficients: 1 Standard + 2 Titrant

Note that for NaOH and KOH,concentration in eq/l is the sameas in mol/l.

d) For alkaline solutions withhigher concentration (1M or 1N forexample), use the same proce-dure but take 40 g of NaOH, or56 g of KOH, for 1000 ml of solu-tion and calibrate the solution byexactly weighing approximately1200 mg of oxalic acid.

Calibration of an Alkaline (NaOH or KOH) Solution

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Alkalinity of Bleach(NaClO Solution)

Introduction

A bleach solution contains mainlyNaClO plus basic products suchas NaOH and Na

2CO

3.

The concentration of basic prod-ucts is generally expressed asNaOH concentration, which isaround 8 g/l NaOH, i.e. 0.2N con-centration.The alkalinity determination usesan acid/base titration.

Principle

The OH- content is simply deter-mined by an acid/base titrationusing a 0.1 eq/l strong acid astitrant.Depending on the bleach solution,the titration curve generally shows2 inflections. The most commonmethod involves a titration of allthe basic functions by a predeter-mined end point titration at pH 4.00.Before this titration, it is necessaryto reduce the ClO- ions present inthe solution.



H2O

2 30% (volume)

Hydrochloric acid 0.1 eq/l (or0.1 mol/l)

Slowly add 8.3 ml of concentratedhydrochloric acid to 500 ml of dis-tilled water and dilute to exactly1000 ml. Calibrate the titrant ver-sus Na

2B

4O

7, 10 H

2O (sodium

borate) as standard.

(See separate application note)

Distilled water



Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1

End point: 4.00 pHStirring delay: 45 secondsMinimum speed: 0.2 ml/minMaximum speed: 8.0 ml/minProportional band: 3.00 pHEnd point delay: 5 secondsSample unit: mlSample amount: 5Titration: Decreasing pHResult: g/l

Procedure

Calibrate the electrode using thetwo IUPAC standards

Pipette 5 ml of sample

Always dilute the sample with thesame volume of distilled water(max. 50 ml)

Slowly add 5 ml of H2O

2 for 5 ml of

sample

Dip electrode and delivery tip inthe solution

Start method by pressing the RUNkey

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Alkalinity of Bleach (NaClO Solution)

Results

Expressed as NaOH content (MW= 40 g/mol) in g/l

As 1 molecule of titrant reacts with1 molecule of NaOH

R(NaOH) = V(titr) * C(titr) * 40 / V(smp)

-V(titr) = total volume of titrant toreach the end point in ml

-V(smp) = sample amount

-C(titr) = exact concentration ofthe titrant in eq/l

For a result in g/l

Enter

The sample amount in the SAMPLEscreen

The titrant concentration in theTITRANT screen

1 Titrant and 1 Sample in theCOEFFICIENTS display

40 for NaOH molecular weight

The Titration Manager gives aresult according the above for-mula.

For a result as a %

As the Titration Manager cannotgive a result in % if the sampleunit is a volumetric unit, you canuse the equation feature:

Equation number: 1Equation result: % NaOHEquation formula:R1 / 10

R1 is the titration result calculatedin g/l.

5 determinations on a commer-cial concentrated bleach

Mean (as NaOH): 7.25 g/lStandard deviation: 0.07 g/lRel. standard deviation: 1%

Working range

Results are expressed in g/l ofNaOH (MW = 40 g/mol)

1 ml of HCl 0.1 eq/l represents4 mg of NaOH or, with a 5 mlsample volume a NaOH contentcorresponding to 0.8 g/l

The working range can be calcu-lated as the following formula:

Result (in g/l) =V(titr in ml) * 0.8 * 1000 / V(smp)

Using the conditions given in thisapplicatin note (5 ml sample and a25 ml burette for titrant), it is pos-sible to obtain results between 7g/l (for 35% capacity of the bu-rette) and 20 g/l (total capacity ofthe burette) with the best possibleaccuracy and reproducibility.

Notes

Addition of H2O

2 is necessary to

reduce the ClO- ion to Cl- beforerunning the alkalinity titration.

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Alkalinity of Water

Introduction

Alkalinity of water is determinedby end point titration with a strongacid solution. "Phenolphthalein"alkalinity corresponds to titratablealkalinity at pH 8.3 and total alka-linity corresponds to titratable al-kalinity at pH 4.5. This applicationnote is an application of interna-tional standard ISO 9963-1.

Principle

The current standard uses HCl0.1 eq/l as titrant but anotherstrong acid such as H

2SO

4 0.1 eq/l

can also be used. If the pH of thewater sample is below 8.3, the"Phenolphthalein" alkalinity is, bydefinition, equal to zero.Results are normally expressedas mmoles/l (or meq/l) of "alkalin-ity", but other units can be used(see notes).If a suitable sensor is used, thealkalinity determination can belinked with a pH and temperaturemeasurement of the sample.


pHC3081-8 Combined pH Elec-trode with temperature sensor(part no. E16M305)

HCl 0.1 eq/l solution in distilledwater

Distilled water

IUPAC Series pH standardspH 4.005 (part no. S11M002) orpH 7.000 (part no. S11M004) andpH 10.012 (part no. S11M007)

End Point Titrationsettings

2 linked methods, one for pHmeasurement and the secondfor alkalinity measurement

pH measurementTemperature: ProbeStability: 25 mpH/minAcceptation time: 45 secondsMax stabilisation time: 2 min

TCA and TA determinationBurette volume: 10 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 2TCA end point: 8.30 pHProportional band: 0.5 pHTA end point: 4.50 pHProportional band: 1.0 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 4 ml/minEnd point delay: 10 secondsSample unit: mlSample amount: 100Titration: Decreasing pHResults: meq/lResults: cumulate

Procedure

This standard can be used with na-tural, drinking and wastewaters withTA between 0.4 and 20 mmoles/l.

Calibrate the electrode withpH 4.005 and pH 10.012 IUPACSeries pH standards.

Pipette 100 ml of water.

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Dip electrode and delivery tip inthe sample.


Results

Expressed as milliequivalents/l(or millimol/l) of OH- alkalinity

R = V(titr) * C(titr) * 1000 / V(smp)

-V(titr) = Total volume of titrant inml, delivered to reach the endpoint (pH 8.3 or pH 4.5)-C(titr) = titrant concentration ineq/l (currently 0.1)-V(smp) = Volume of the sample(currently 100 ml)

For a result in mmol/l

Enter




The Titration Manager gives aresult according the above formula.

Results for 5 determinations inmilliequivalents/lMean: 3.6Standard deviation: 0.038Relative standard deviation: 1%

Working range

The sample size and titrant con-centration depend on the qualityof the water.Using the application note settings

V sample = 100 mlBurette volume = 10 mlTitrant concentration = 0.1 eq/l

For the best accuracy and repro-ducibility, the result range is be-tween 3.5 meq/l (or 175 mg/lCaCO

3) for 35% of the cylinder

burette capacity and 10 meq/l (or500 mg/l CaCO

3) for the burette

capacity.

With the same conditions, the"experimental" limit correspondingto a titrant volume of 0.5 ml is0.5 meq/l (or 25 mg/l CaCO

3).

For alkalinity below this value, it isrecommended to use a low alka-linity method with 0.02 eq/l titrantand 200 ml for sample volume,using the calculation above.

Notes

1) The results are normally ex-pressed in mmoles/l (or meq/l) ofalkalinity.1 ml of 0.1 eq/l of strong acid rep-resents 0.1 meq or mmol of alka-linity.

Alkalinity of Water

2) Depending on the country,many other units can be used forthe results

-mmol/l CaCO3

(= meq/l * 0.5)(CO3

-- has 2 alkalinity functions per mol-ecule)

-mg/l CaCO3

(= meq/l * 50)(MW of CaCO3 is 100.09 g/mol with 2alkaline functions per molecule)

-mg/l HCO3- (= meq/l * 61)

(MW of HCO3- is 61 g/mol with 1 alkalinefunction per molecule)

-Clark degree (= meq/l * 3.50)

-German degree (= meq/l * 2.80)

-French degree (= meq/l * 5.0)

-U.S. degree (= meq/l * 2.90)

It is easy to express results in allthese units thanks to the equationfeatures of the Titration Manager.

Bibliography

International standard ISO 9963

EPA method number 310.1

Standard methods for water andwastewater 18th edition (1992)2-25 part 2320

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Titratable Acidityin Wines or Juices

Introduction

Titratable acidity is used as aguide to determine how acidic theproduct will taste. This determina-tion measures the concentrationof all available hydrogen ionspresent in the sample, wine orjuice.It is a weak acid titration using astrong base such as NaOH andthe equivalence point (or end point)occurs at a pH greater than pH 7.00.Depending on local procedures,the end point can vary betweenpH 7.5 and pH 8.4.We use pH 8.2, the most com-monly used value, in the followingapplication.

Principle

The end point titration at pH 8.2 isvery easy to run. The titrant isnormally NaOH 0.1 eq/l. The winesample needs to be degassedbefore determination.The result is normally expressed ing/l tartaric acid (MW = 150.09 g/moland 2 acid functions).

Tartaric acid =HOOC-(CHOH)

2-COOH



NaOH 0.1 eq/l solution in distilledwater (see Application NoteTTEP01-02MIN)

Distilled water

Check the pH of the distilled wa-ter. Using the titration manager asa pH-meter, adjust the distilledwater to pH 8.2 by means of a fewdrops of base or acid solution.

IUPAC Series pH standardspH 4.005 (part no. S11M002) orpH 7.000 (part no. S11M004) andpH 10.012 (part no. S11M007).


Burette volume: 10 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.20 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 5 ml/min

Proportional band: 4.00 pHEnd point delay: 5 secondsSample unit: mlSample amount: 10Titration: Increasing pHResult: g/l

Procedure

A wine sample can be degassedin two ways:

1) Pour the wine into a Buchnerflask and connect it to a vacuumsystem for 3 minutes.

2) Boil the wine for a few secondsthen allow the wine to cool toroom temperature.

Calibrate the combined pH elec-trode using the 2 IUPAC standardsabove.

Pipette 10 ml of sample.

If necessary, add pH adjusteddistilled water.



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Results

Expressed as g/l of tartaric acidusing eq/l or mol/l as titrant unit2 molecules of NaOH react with1 molecule of tartaric acid

R = V(titr) * C(titr) * 150.09 / V(smp) * 2


-C(titr) = Titrant concentration ineq/l (currently 0.1)

-V(smp) = sample volume

150.09 = molecular weight of tar-taric acid

2 = Ratio between titrant andsample (2 titrants react with 1sample)

For a result in g/lEnter

The volume sample in the SAMPLEscreen

The titrant concentration in theTITRANT screen,

2 Titrants and 1 Sample in theCOEFFICIENTS display

150.09 as molecular weight.

The Titration Manager will give aresult according the formulaabove.

For 5 determinations on wineMean (as tartaric acid in g/l): 5.3 g/lStandard deviation: 0.025 g/lRel. standard deviation: 0.5%

Working range

With current figures (0.1 for C(titr)and 10 for V(smp) and a low limitaround 0.5 for V(titr) we can con-sider 0.375 g/l as an experimentallimit.Using application note conditions(10 ml volume sample and 10 mltitrant burette) it is possible toobtain results between 2.60 g/l(for 35% capacity of the burette)and 7.40 g/l (capacity of the bu-rette) with the best possible accu-racy and reproducibility.If the result is different from thatexpected, change cylinder capac-ity of the burette and/or the sam-ple volume.For samples with very low acidityyou can also use a low concentra-tion titrant (0.02 eq/l titrant gives alow limit for the result equal to0.075 g/l for a 10 ml sample).You can also take a larger amountof sample.

Notes

1) Normally the result is expressedas g/l of tartaric acid1 ml of NaOH 0.1 eq/l represents7.5 mg of tartaric acid

2) Depending on local regulations,other acids can be used for theexpressed result; for example

Acetic acid (1 ml of NaOH0.1 eq/l = 6.005 mg)

Citric acid (anhydrous) (1 ml ofNaOH 0.1eq/l = 6.40 mg)

Lactic acid (1 ml of NaOH0.1 eq/l =9.01 mg).

Titratable Acidity in Wines or Juices

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Acidity of Milk

Introduction

As the acidity has a major influ-ence on the taste of the product,this parameter is used to test thequality of milk.As the acidity of milk increaseswith the storage time, this param-eter is also a means of checkingstorage conditions.

Principle

The acidity of milk is determinedby end point titration using 0.1 eq/lNaOH. The end point value is gen-erally fixed at pH 8.7 and the re-sult is expressed in dg/l of lacticacid. This result is also calledDORNIC acidity.


pHC2401-8 Combined pH Elec-trode (part no.E16M400)




Burette volume: 10 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.70 pHStirring delay: 20 secondsMinimum speed: 0.2 ml/minMaximum speed: 6.0 ml/minProportional band: 4.00 pHEnd point delay: 5 secondsSample unit: mlSample amount: 20pH: IncreasingResult: g/lEquation: Result * 10

Procedure

Calibrate the combined pH elec-trode using the two IUPAC stand-ards above.

Pipette 20 ml of sample into a lowvolume beaker (RadiometerAnalytical beakers part no. 904-488for 50 pcs. can be used).


Do not dilute the sample.


Results

Expressed as decigrams/l oflactic acid (CH3-CHOH-COOH)and MW=90 g/molAs in this case 1 molecule ofNaOH reacts with 1 molecule oflactic acid

R = V(titr) * C(titr) *90 * 10* / V(smp)



-V(smp = sample volume in ml

90 = Molecular weight of lacticacid

10 = Factor for result expressionin decigram/l

If you enter the correct data fortitrant concentration, sampleamount, molecular weight, thetitration manager's reaction coeffi-cients and equations allow theresult to be calculated.

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90 for lactic acid molecular weight

The Titration Manager gives a resultaccording to the formula above.

You can obtain a first resultdirectly in g/l of lactic acid andthen use an equation to obtainanother result in decigrams/l

For a result in decigrams/luse the equation featureEquation number: 1Equation result: dg/lEquation formulaR1 * 10

R1 is the titration result calculatedin g/l

Results for 10 determinationsMean (as decigrams/l of lacticacid): 15.17Standard deviation: 0.106Relative standard deviation: 0.7%

Working range

The acidity of fresh milk is around15 to 17 when expressed, as indi-cated, in decigrams/l of lactic acid(some articles give a mean valueof around 18). According to thecalculation formula and for 20 mlof sample, this value correspondsto approximately 4 ml of 0.1 eq/ltitrant.

Notes

1) Depending on local applications,it is recommended to use a N/9(0.1111 eq/l) titrant.With this titrant concentration anda sample volume equal to 10 ml:

Acidity (in decigrams/l of lacticacid) = V(titrant) * 10

2) According to another definition,acidity of milk can be expressed inSoxlet-Henkel acidity: i.e. thenumber of ml of 0.25 eq/l titrantneeded to titrate 100 ml of milk.

For a 10 ml sample volume

Acidity in °S-H = V(titrant) * 10 /2.5

Fresh milk corresponds to aSoxlet-Henkel acidity of around 7.2(generally between 6.5 and 7.5).

3) The end-point value is impor-tant for this method. Please referto local rules or standards.

4) This method frequently uses acoloured indicator. To adapt thepH determination, use the col-oured indicator the first time andread the pH of the sample accord-ing to the colour change.

Acidity of Milk

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Acidity of Mustardand Associated Products

Introduction

The total acidity of mustard andmany associated products suchas mayonnaise refers to the sumof titratable acids using a stronglyalkaline titrant like NaOH.An end point titration can easily beused with pH 7.50 as end point.Depending on the sample andlocal regulations, results are ex-pressed as acetic acid content ing/l or mg/g or even as a %.This method is not suitable foredible oils, because they are notmiscible with water.

Principle

The end point titration is very easyto run. The titrant is normally NaOH0.1 eq/l.As the result is expressed as ace-tic acid content, the MW ofCH

3COOH is 60 g/mol.




Distilled water

IUPAC Series pH standard solu-tions pH 4.005 (part no. S11M002)and pH 7.000 (part no. S11M004)


Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 7.50 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 8.0 ml/minProportional band: 3.50 pHEnd point delay: 5 secondsSample unit: g

(depending to the sample can bealso ml)

Sample amount: (see below)Titration: Increasing pHResult: %

Procedure

Dilute the sample in 50 or 100 mlof freshly distilled water.For some samples an efficientstirring procedure may be neces-sary.

Calibrate the combined pH elec-trode using pH 4.005 and pH7.000 IUPAC standards.

Dip electrode and delivery tip thesample.


Results

As in this case 1 molecule of ti-trant reacts with 1 molecule ofCH

3COOH

Expressed as g/l acetic acidR = V(titr) * C(titr) * 60.0 / V(smp)

Expressed as mg/g acetic acid(or g/kg)R = V(titr) * C(titr) * 60.0 *FDIL / W(smp)

Expressed as % acetic acidR = V(titr) * C(titr) * 60.0 *FDIL / 10 * W(smp)

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-W(smp) = sample amount in g

-V(smp) = Sample volume in ml

-FDIL = Dilution factor betweenthe total volume used to dilute thesample and the aliquot used fortitration.

For a result as a %Enter

The actual sample amount in theSAMPLE screen



60 as molecular weight

The Titration Manager gives theresult according the above formula.

As the above-mentioned dilutionfactor FDIL is directly calculated bythe titration manager, if necessaryenter the following in the SAMPLEscreen.

DILUTION: YES

The total sample amountThe final dilution volumeThe aliquot volume

5 determinations on mustardMean: 1.8%Standard deviation: 0.009Rel. standard deviation: 0.5%

Working range

Using application note conditions(0.1 for titrant concentration and25 ml burette cylinder and 10 mlfor sample volume), the workingrange is between 5.25 g/l (for 35%capacity of the burette) and 15 g/l(for the burette capacity) for thebest reproducibility.For 10 g of sample and FDIL=1the experimental working range isbetween 5.25 g/kg and 15 g/kg orbetween 0.52% and 1.5%.

Notes

1) With some non-homogeneousproducts, it is necessary to ensureefficient stirring during titration. Inthis case, you can also use loweraddition speeds and a longer endpoint delay (15 seconds for exam-ple)

2) According to different regula-tions or standards, the pH of theend point can be changed butother settings stay identical.

Acidity of Mustard and Associated Products

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Acidity of Cheese

Introduction

As the acidity of cheese has amajor influence on the taste of theproduct, this parameter is used totest the quality.

Principle

The acidity of cheese is deter-mined by end point titration using0.1 eq/l NaOH. The end pointvalue is generally fixed at pH 8.4and the result is expressed in %of lactic acid, which has a MW of90.08 g/mol.


pHC2401-8 Combined pH Elec-trode (part no.E16M400).

NaOH 0.1 eq/l solution in distilledwater (see Application NoteTTEP01-02MIN).



Burette volume: 10 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.40 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minProportional band: 4.00 pHEnd point delay: 5 secondsTitration: Increasing pHSample unit: gSample amount: see belowResult: %

Procedure

Sample preparationPlace a known amount of cheese(generally between 10 and 20 g)in a 250 ml beaker, add 100 ml ofdistilled water at 40°C and homog-enise with a high speedhomogeniser. Filter or centrifugeaccording to particular recommen-dations and dilute to 250 ml usinga volumetric flask. Titrate an ali-quot of 25 or 50 ml for example.

TitrationCalibrate the combined pH elec-trode using the 2 IUPAC standardsabove.

Pipette 25 or 50 ml of sample.



Results

Expressed as % of lactic acid(CH3-CHOH-COOH with a MW of90.08 g/mol)

As in this case 1 molecule of ti-trant reacts with 1 molecule oflactic acid

R = V(titr) * C(titr) * 90.08 * 100 * F /1000 * W(smp)



-W(smp = sample amount in g

90.08 = Molecular weight of lacticacid

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F = Dilution factor between totalvolume and aliquot

100 = Factor needed for a resultexpressed in %

For a result in %Enter




90.08 as molecular weight

The Titration Manager gives aresult according to the above for-mula.

You can also use the dilution cal-culation formula of the titrationmanager.

In the SAMPLE screen

Dilution YESEnter the total sample amountEnter the final dilution volume in mlEnter the aliquot volume in ml

5 determinationsMean: 0.97%Standard deviation: 0.01%Rel. standard deviation: 1%

Working range

For a dilution factor of 10 and 10 gas sample amount, and for a titrantvolume corresponding to 0.5 ml asan experimental detection limit fortitrant consumption, the result limitis close to 0.45%.

Acidity of Cheese

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Total Titratable Acidityin Vinegar

Introduction

Besides the taste, the quality of avinegar depends on various fac-tors such as pH and total titratableacidity. As this determination isrun by titration with a strong basicsolution (NaOH 1 or 0.5 M), theend point titration is between pH8.0 and pH 8.8 depending on themanufacturing conditions.

Principle

The end point titration for this ap-plication note, based on experi-ments at pH 8.2, is very easy torun. Vinegar is diluted beforeanalysis with freshly distilled water;the titrant is NaOH 1M or 0.5 M.The result is expressed ing/100 ml (or %) of CH3COOH(MW=60 g/mol)



NaOH 0.5 or 1 eq/l solution indistilled water (see ApplicationNote TTEP01-02MIN)

Distilled water



Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.20 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minProportional band: 3.00 pHEnd point delay: 5 secondsSample unit: mlSample amount: 10Titration: Increasing pHResult: g/l

Procedure

As the end point of the titrationdepends on the vinegar, refer toyour local procedure or determinethe end point value by means of amanual titration (manual dosing).

Calibrate the pHC2401-8 electrodeusing 2 of the 3 above-mentionedIUPAC standards.

Prepare the burette with the 1M or0.5M NaOH titrant.


Add 50 ml of freshly distilled water.



Results

Expressed as g/100 ml (or %) ofCH3COOH

R = V(titr) * C(titr) * 60 * 100 / V(smp) * 1000



-V(smp) = sample volume in ml

60 = molecular weight of CH3COOH

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For a result in %Enter

A first result unit as g/l




60 as molecular weight

As the Titration Manager cannotgive a result as a % if the sampleunit is a volumetric unit, use theequation feature:

Equation number: 1Equation result : % CH

3COOH

Equation formulaR1 / 10

R1 is the titration result calculatedin g/l.

For 5 determinationsMean (as g/100 ml of CH

3COOH):

7.2 g/100 mlStandard deviation:0.058 g/100 mlRel. standard deviation: 0.8%

Working range

Irrespective of manufacturing dif-ferences, commercially availablevinegars generally have a totaltitratable acidity of between 4 and8%. For a 10 ml sample amount,this corresponds to 0.4 to 0.8 g ofacetic acid and 1 ml of NaOH 1Mcorresponds to 0.06 g ofCH

3COOH.

Notes

Differences in standards or proce-dures may lead the end point tobe fixed at a pH higher than 9.5.

In this case, use the pHC2011-8Combined pH Electrode (partno. E16M317) instead of thepHC2401-8.

Total Titratable Acidity in Vinegar

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Titratable Acidity and FormolNumber in Fruit Juices

Introduction

The formol number, or formol titra-tion, measures the total aminoacid (NH

2-R-COOH) concentra-

tion. Using 2 successive end pointtitrations, it is possible to deter-mine total titratable acidity andformol number.

Principle

The determination of formolnumber takes place in three steps:

1) Neutralisation of titratable acid-ity by means of an end point titra-tion at pH 8.2 with NaOH 0.1 eq/l

2) Addition of an excess of formol(HCHO) to the solution. This op-eration locks the NH

2 groups of

amino acids due to the decreasein pH and allows titration of theCOOH groups of amino acids withan end point titration at pH 8.2

3) Second endpoint titration at pH8.2 to determine total amino acidcontent. The result is then ex-pressed as milliequivalents/100 mlor milliequivalent/l



NaOH 0.1 eq/l solution in distilledwater (see separate applicationnote)

Distilled water

Check the pH of the distilled wa-ter. Using the titration manager asa pH meter, adjust the distilledwater to pH 8.2, by means of fewdrops of base or acid solution,with NaOH 0.1 as titrant

Formol (HCHO) solution at 37%adjusted to pH 8.2

IUPAC Series pH standardspH 4.005 (part no. S11M002) orpH 7.000 (part no. S11M004) andpH 10.012 (part no. S11M007)


Two linked methodsFirst method (can be used astitratable acidity)Burette volume: 10 mlMaximum volume: 30 ml

Stirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.20 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minProportional band: 3.00 pHEnd point delay: 10 secondsSample unit: mlSample amount: 10Result expression: g/l

(of tartaric acid or citric acid)Titration: Increasing pH

Second method (Formol numberdetermination)Burette volume: 10 mlMaximum volume: 10 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 8.20 pHStirring delay: 60 secondsMinimum speed: 0.2 ml/minMaximum speed: 5 ml/minProportional band: 2.00 pHEnd point delay: 10 secondsSample unit: mlSample amount: 10Result expression: meq/100 mlTitration: Increasing pH

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Procedure

Connect the electrode to the elec-trode input.

Calibrate the electrode using thetwo IUPAC standards above.

Stir and pipette 10 ml of sample.

Always dilute the sample with thesame volume of distilled water(25 ml for example).


Start titration by pressing the RUNkey.

At the end of the first methodmanually add 5 ml of HCHO solu-tion for 10 ml of sample to thesample solution.

Results

For titratable acidity expressedas g/l of tartaric acid(HOOC-(CHOH)2-COOH)

Result is normally expressed as g/lof tartaric acid (MW= 150.09 g/moland 2 acid functions).As 2 molecules of NaOH reactwith 1 molecule of tartaric acid:

R = V(titr) * C(titr) * 150.09 / V(smp) * 2



-V(smp) = sample volume

150.09 = molecular weight of tar-taric acid

2 = Ratio between titrant andsample

For titratable acidity in g/l oftartaric acidEnter in the first method

The actual sample amount in theSAMPLE screen in ml

The titrant concentration in theTITRANT screen in mol/l or eq/l




For titratable acidity in g/l ofcitric acid (that has 3 acid func-tions with a MW of 192.4)Enter in the first method






For Formol number expressedas meq/l

Formol no. = V(titr) * C(Titr) *1000/ V(smp)

-V(titr) = total volume of titrant toreach the end point in ml-C(titr) = Titrant concentration ineq/l or mol/l (currently 0.1)-V(sample) = sample volume in ml

For formol number in meq/100mlEnter in the second method



1 Titrant and 1 Sample in the CO-EFFICIENTS display (if necessary)

Enter in the RESULT screenResult: 1Unit: eq/lEquation: 1Formula: R1/10Name: meq/100 ml

The Titration Manager gives 2results:Result expressed in meq/lResult from equation formula,expressed in meq/100 ml

Titratable Acidity and Formol Number in Fruit Juices

3 determinations on grapefruitjuiceAcidityMean: 15.28 g/l tartaric acidStandard deviation:

0.02 g/l tartaric acidRel. standard deviation: 0.13%

Formol numberMean: 2.19 meq/100 mlStandard deviation:

0.038 meq/100 mlRel. standard deviation: 1.7%

Working range

Related to the calculation formula,using 10 ml for sample volumeand 0.1 eq/l titrant concentration.For acidity determination 1 ml oftitrant corresponds to 0.75 g/l oftartaric acid.For formol number determination:

Formol no. (meq/100 ml) = V(titr) in ml

For a 10 ml burette, formol numberrange can be estimated between0.2 (experimental low limit corre-sponding to 0.2 ml) and 10 (nomi-nal value of cylinder capacity):

Formol no. (meq/l) =Formol no. (meq/100 ml) * 10

Notes

Depending on local procedures,the first end point can vary be-tween pH 8.0 and pH 8.4.

The most commonly used value ispH 8.2. We use this value in thisapplication.

It is also possible to have differentvalues for the pH end points (forexample, pH 8.1 for the first andpH 8.4 for the second).

Adjust the pH of the formol solu-tion to the same value as thatused in the second end point titra-tion (formol number determina-tion).

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Analysis of a Finishing Bath

Introduction

In the car industry, the finishingbath is used just before the phos-phatation bath. The main compo-nents of this bath are metallicphosphates, titanium for example.The analysis of the bath consistsof measuring the total alkalinity ofthe solution with H

2SO

4 0.1N as

titrant. As the titration curve isvery well defined, it is possibleperform an automatic titration witha combined glass electrode with apre-set end point detection.

Principle

The results are expressed as"points", i.e. the number of ml oftitrant 0.1N used to titrate a givensample amount.

As this titration was initially runwith a coloured indicator (bromo-cresol green), the pre-set endpoint can be fixed to pH 4.77.

The sample amount is generallyabout 100 ml.



H2SO

4 0.1 eq/l solution in distilled

water

Distilled water



Burette volume: 10 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1Endpoint: 4.77 pHStirring delay: 30 secondsMinimum speed: 0.4 ml/minMaximum speed: 6.0 ml/minProportional band: 2.0 pHEnd point delay: 5 secondsSample unit: mlSample amount: 100Titration: Decreasing pHResult: ml

Procedure

Calibrate the electrode withpH 4.005 and pH 10.012 IUPACstandards.

Pipette 100 ml, or the asked vol-ume of sample.

If dilution is necessary, alwaystake the minimum and constantvolume of distilled water.



Results

Expressed as ml of 0.1 eq/ltitrant for 100 ml of sample

R = V(titr)

If the titrant used is not exactly0.1 eq/l in concentration and if thesample amount is not 100 ml,correct as follows:

R = V(titr) * 100 * C(titr) / V(smp) * 0.1

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-V(titr) = total volume of titrant toreach the end point (pH 4.77) in ml

-V(smp) = current sample amount

-C(titr) = exact concentration ofthe titrant

Depending on local industry regu-lations, the reference volume maynot be 100 ml.

4 determinations. Results inpoints for 100 ml samplesMean: 2.50 mlStandard deviation: 0.050 mlRel. standard deviation: 2%

Working range

As the result for a 100 ml samplevolume and a 0.1 eq/l titrant isdirectly the delivered volume oftitrant (for the best possible accu-racy and reproducibility), theworking range is between 3.5 and10 ml for the application note con-ditions.

Notes

1) Reliability of an end point titra-tion depends on the behaviour ofthe working electrode.

2) For this bath, it is necessary toregularly check the electrode.

3) After a cycle of measurements(10 or even 5 titrations) check theelectrode, for example by measur-ing the IUPAC standard pH 10.012or by a new calibration procedure.

Analysis of a Finishing Bath

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Total and Free Alkalinityof a Cleaning Bath

Introduction

In the car industry, a cleaning bathis generally a mixture of a strongbase (typically NaOH) with othersalts, phosphates, silicates orborates for example. The analysisaims to determine the free orstrong alkalinity (free OH-) and thetotal alkalinity corresponding tothe sum of weak bases.Free and total alkalinity can bedetermined on the same sampleby end point acid-base titration attwo different end points, pH 7.7 forthe first and pH 4.0 for the second.Usually the titrant is 0.1 eq/l H

2SO

4.

Principle

The sample amount is generallybetween 25 and 100 ml.

Results are expressed as anumber of ml of 0.1 eq/l titrantnecessary to reach the end point(pH 7.7 or pH 4.0) for a 100 mlsample volume.



0.1 eq/l H2SO

4 in distilled water

Distilled water



Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 2First end point: 7.70 pHProportional band: 2.0 pHSecond end point: 4.00 pHProportional band: 2.0 pHStirring delay: 30 secondsMinimum speed: 1.25 ml/minMaximum speed: 10 ml/minEnd point delay: 5 secondsSample unit: mlSample amount: 100Titration: Decreasing pHResult: mlResults: cumulate

Procedure

Calibrate the electrode withpH 4.005 and pH 10.012 IUPACstandards.

Pipette 100 ml or the requiredvolume of sample.

If dilution is necessary, alwaystake the minimum and constantvolume of distilled water.



Results

Expressed as ml of 0.1 eq/ltitrant for 100 ml of sample

R = V(titr)

If the titrant used is not exactly0.1 eq/l in concentration and if thesample amount is not 100 ml,correct as follows:

R = V(titr) * 100 * C(titr) / V(smp) * 0.1

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-V(titr) = total volume of titrant toreach the end point (pH 7.7 orpH 4.0) in ml



Depending on local industry regu-lations, the reference volume maynot be 100 ml.

5 determinations. Results inpoints

FREE ALKALINITYMean: 6.46 mlStandard deviation: 0.009 mlRel. standard deviation: 0.15%

TOTAL ALKALINITYMean: 14.76 mlStandard deviation: 0.012 mlRel. standard deviation: 0.09%

Working range

As the result for a 100 ml samplevolume and a 0.1 eq/l titrant isdirectly the delivered volume oftitrant (for the best possible accu-racy and reproducibility), theworking range is between 8.75and 25 ml for the application noteconditions.

Taking into account the differencebetween free and total alkalinity,the free alkalinity is sometimesbelow the range but the reproduc-ibility is nevertheless acceptable.

Total and Free Alkalinity of a Cleaning Bath

Notes

1) It is not difficult to run this endpoint titration method. Pay atten-tion to the result, which is not al-ways calculated as indicated inthis application note. Do not forgetthat the volumes used for resultsare total volumes from startingtitration to the end point.

2) Reliability of an end point titra-tion depends on the electrodeused. Check the combined pHelectrode regularly, for exampleafter a series of 5 determinations.

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NaOH and HCHO inElectroless Copper Bath

Introduction

Chemical copper baths, used inparticular in the manufacture ofprinted circuits, contain coppersalts, sodium hydroxide stabilisingagents and formol.The sodium hydroxide concentra-tion of the bath is generally be-tween 8 and 12 q/l. Formol con-centration is between 3 and 8 g/l.The HCHO determination uses anend point acid/base titration afterOH- titration (end point titration atpH 10.00) and addition of Na

2SO

3.

Principle

HCHO determination in a copperbath takes place in three steps:

1) Neutralisation of the sample topH 10.00. This first step can beused as a NaOH determination(see separate application note)

2) Addition to the sample of aNa

2SO

3 solution. This addition

allows the following reaction

HCHO + Na2SO3 + H2O � NaSO3-CH2OH + NaOH

which releases one OH- ion forone HCHO molecule

3) End point titration of releasedOH- which allows the HCHO de-termination



Hydrochloric acid 0.1 eq/l

Slowly add 8.3 ml of concentratedhydrochloric acid to 500 ml of dis-tilled water and dilute to exactly1000 ml. Calibrate the titrant ver-sus Na

2B

4O

7,10 H

2O (sodium bo-

rate) as standard.

Distilled water

1M Na2SO

3 solution:

Dissolve 126 g of Na2SO

3 in a

beaker containing 800 ml of dis-tilled water. With a few drops of1M NaOH, adjust the pH of thesolution to 10.00 using the Titra-tion Manager fitted with thepHC2011-8 electrode as a pHmeter. Adjust to 1000 ml with dis-tilled water.It is necessary to adjust the pHof the Na

2SO

3 solution to 10.00

because the first step of the

procedure is performed by endpoint titration at pH 10.00.



Two linked methodsFirst method (can be used as OH-

determination)Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 10.00 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minProportional band: 3.00 pHEnd point delay: 10 secondsSample unit: mlSample amount: 5Result expression: g/lTitration: Decreasing pH

Second method (HCHO determi-nation)Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1

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End point: 10.00 pHStirring delay: 60 secondsMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minProportional band: 3.00 pHEnd point delay: 10 secondsSample unit: mlSample amount: 5Result expression: g/lTitration: Decreasing pH

Procedure

Connect the combined pH elec-trode to the E1 electrode input

Calibrate the combined pH elec-trode using the 2 above IUPACstandards


Always dilute the sample with thesame volume of distilled water (donot exceed 50 ml)


Start titration by pressing the RUNkey

At the end of the first method,manually add 10 ml of Na

2SO

3solution to the sample solution for5 ml of sample aliquot.

Results

As in this case 1 molecule of ti-trant reacts with 1 molecule ofNaOH or HCHOExpressed as NaOH content(MW = 40 g/mol) and HCHOcontent (MW = 30 g/mol) in g/l


R(HCHO) = V(titr) * C(titr) * 30 / V(smp)




NaOH and HCHO in Electroless Copper Bath


The sample amount used in theSAMPLE screen


1 Titrant and 1 Sample in theCOEFFICIENTS display for thetwo methods

40 for NaOH molecular weight inthe first method

30 for HCHO molecular weight inthe second method


Results and statistics for NaOHand HCHO

10 determinations on the samebath (NaOH)Mean (as NaOH): 8.8 g/lStandard deviation: 0.04 g/lRel. standard deviation: 0.5%

5 determinations on the samebath (HCHO)mean (as HCHO): 2.66 g/lStandard deviation: 0.011 g/lRel. standard deviation: 0.43%

Working range

Results are expressed in g/l ofNaOH (MW = 40 g/mol) and g/l ofHCHO (MW = 30 g/mol)

1 ml of HCI 0.1 eq/l represents 4mg of NaOH and 3 mg of HCHOor, with a 5 ml sample volume, aNaOH content corresponding to0.8 g/l and a HCHO content of0.6 g/l

The working range can be calcu-lated as the following formula

Result (in g/l) = V(titr in ml) * 0.8 * 1000 /V(smp) for NaOH

And

Result (in g/l) = V(titr in ml) * 0.6 * 1000 /V(smp) for HCHO

Using application note conditions(5 ml volume sample and 25 mltitrant burette), it is possible toobtain results between 7 g/I NaOHand 5 g/l HCHO (for 35% capacityof the burette) and 20 g/l NaOHand 15 g/l HCHO (total burettecapacity) with the best possibleaccuracy and reproducibility.

Notes

1) The stirring delay set in thesecond method allows the opera-tor to add the Na

2SO

3 solution. You

can choose to reduce this time.

2) Result is expressed in g/l HCHO

1 eq/l represents 3 mg of HCHO

Ensure you use a high alkalinityelectrode such as the pHC2011-8

3) Always calibrate the pH com-bined electrode using IUPACstandard pH 10.012 (part no.S11M007)

4) If your own procedure works ata pH other than pH 10.00, adjustthe Na

2SO

3 solution to the same

pH.

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NaOH in Electroless Copper Bath

Introduction

Chemical copper baths, used inparticular in the manufacture ofprinted circuits, contain coppersalts, sodium hydroxide stabilisingagents and formol.The sodium hydroxide concentra-tion of the bath is generally be-tween 8 and 12 g/l. Formol con-centration is between 3 and 8 g/l.The NaOH determination uses anacid/base titration.

Principle

The OH- content is simply deter-mined by an acid/base titrationusing a 0.1 eq/l strong acid astitrant.



Hydrochloric acid 0.1 eq/l

Slowly add 8.3 ml of concentratedhydrochloric acid to 500 ml of

distilled water and dilute to exactly1000 ml. Calibrate the titrant ver-sus Na

2B

4O

7,10 H

2O (sodium bo-

rate) as standard (see separatenote)

Distilled water



Burette volume: 25 mlStirring speed: 400 rpmWorking mode: pHNumber of end points: 1End point: 10.00 pHStirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minProportional band: 3.00 pHEnd point delay: 10 secondsSample unit: mlSample amount: 5Titration: Decreasing pHResult: g/l

Procedure

Calibrate the combined pH elec-trode using the 2 IUPAC stand-ards above.


Dilute the sample with the samevolume of distilled water each time(no more than 50 ml maximum).



Results

Expressed as NaOH content(MW = 40 g/mol) in g/lAs in this case 1 molecule of ti-trant reacts with 1 molecule ofNaOH:




-C(titr) = exact concentration ofthe titrant in eq/l

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40 for NaOH molecular weight inthe first method


10 determinations on the samebathMean (as NaOH): 8.8 g/lStandard deviation: 0.04 g/lRel. standard deviation: 0.5%

Working range

Results are expressed in g/l ofNaOH (MW = 40 g/mol)

1 ml of HCl 0.1 eq/l represents4 mg of NaOH or, with a 5 mlsample volume, a NaOH contentcorresponding to 0.8 g/l

The working range can be calcu-lated according to the followingformula

Result (in g/l) = V(titr in ml) * 0.8 * 1000 / V(smp)

Using application note conditions(5 ml volume sample and 25 mltitrant burette), it is possible toobtain results between 7 g/l (for35% capacity of the burette) and20 g/l (for burette capacity) withthe best possible accuracy andreproducibility.

For other NaOH contents, changethe burette cylinder capacity and/or sample volume.

NaOH in Electroless Copper Bath

Notes

1) Ensure you use use a high al-kalinity electrode such as thepHC2011-8.

2) Before starting a determinationcycle, always calibrate the com-bined pH electrode usingpH 10.012 standard (part no.S11M007).

3) According to certain bathmanufacturer's protocols, the pHvalue for the end point titration canchange and be between 9.5 and10.50.

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Boric Acid in Plating Baths

Introduction

Nickel, cobalt or zinc acid platingbaths generally consist of a mix-ture of boric acid and a metallicsalt of the corresponding metal.The boric acid can be determinedby means of an acid-base titrationafter addition of D-mannitol.Depending on the formulation ofthe bath, boric acid concentrationis generally around 25 g/l.

Principle

In the presence of excess D-man-nitol, boric acid forms a complexgiving a strong acidic compoundeasily titratable by sodium hydrox-ide.

The reaction is

For boric acid neutralisation (molarweight = 61.83 g/mol)

H3BO

3 + OH- � H

2BO

3- + H

2O


pHC2401-8 Combined pHElectrode (part no. E16M317)

1M NaOH (1.0 mol/l or eq/l) (seeseparate note)

Distilled water


D-Mannitol 200 g/l in distilled water


Burette volume: 25 mlMaximum volume: See below

(working range)Stirring speed: 400 rpmWorking mode: pHNumber of end points: 1First end point: 6.60 pH (see note 6)Stirring delay: 45 secondsMinimum speed: 0.2 ml/minMaximum speed: 5 ml/minProportional band: 3.00 pHEnd point delay: 10 secondsSample unit: ml

Sample amount: 5Titration: Increasing pHResult: g/lMolar weight: 61.83Coefficients: 1 sample and 1 titrant

Procedure

Calibrate the electrode using the 2IUPAC standards above.


Add 50 ml of the mannitol solution.

If necessary add a few ml of dis-tilled water.



Results

Generally expressed in g/l boricacidAs 1 mole of titrant reacts with1 mole of boric acid

R(Boric acid) = V(titr) * C(titr) * 61.83/ V(smp)

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-C(titr) = exact concentration ofthe titrant in mol/l

-61.83 = molecular weight of boricacid

For results in g/lSettings indicated above for ENDPOINT TITRATION allow the Titra-tion Manager to give results ac-cording to the above formula.

3 determinations on a zinc bathMean: 25.10 g/l boric acidStandard deviation:

0.08 g/l boric acidRel. standard deviation: 0.32%

Working range

Corresponding to the applicationnote conditions (titrant concentra-tion 1 mol/l, 5 ml for sample vol-ume) and the above-mentionedformulas.

1 ml of titrant:

Corresponds to 12.36 g/l of boricacid content

Corresponding to the expectedvalues for results, this calculationcan easily determine the maxi-mum volume for titration.

An acid nickel bath contains be-tween 40 and 50 g/l of boric acidand also 80 g/l of nickel; an acidzinc bath contains around 25 g/l ofboric acid and 30 to 40 g/l of zinc.

Boric Acid in Plating Baths

Notes

1) In order to obtain correct re-sults, this titration needs a largeamount of excess mannitol,especially for zinc baths.

2) Solid state mannitol can beadded to the solution, in this caseadd distilled water and 10 g ofmannitol.

3) If the amount of excess manni-tol is correct, the starting pH isnormally below 4.00.

4) It may be necessary to heat theplating bath to 60°C beforepipetting just to dissolve the pre-cipitate.

5) Using a titrant with a lower con-centration (0.2 M or 0.5 M for ex-ample) can improve the accuracyof the results.

6) Depending on the bath composi-tion (nickel, zinc or cobalt) the pHof the end point can change. Todetermine the value of the endpoint, for the first run, take an endpoint of 10.00 pH to obtain thecomplete curve, and then byvisual examination, determine theend point generally situated be-tween 6.4 pH and 7.5 pH.

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Boric Acid and Nickel ContentDetermination

Introduction

Nickel is commonly used as plat-ing in surface treatment or prepa-ration industries. In some cases,in particular for bright plating, thebath consists of a mixture of boricacid and nickel salt.The boric acid can be determinedby means of an acid-base titration.Bright nickel baths generally con-tain 40 to 50 g/l of boric acid and60 to 80 g/l of Ni (MW of Ni58.69 g/mol)

Principle

In the presence of excess D-man-nitol, boric acid forms a complexgiving a strong acidic compoundeasily titratable by sodium hydrox-ide.

The reaction is

For boric acid neutralisation (molarweight = 61.83 g/mol)

H3BO

3 + OH- � H

2BO

3- + H

2O

After boric acid neutralisation, the

precipitation of Ni(OH)2 occurs

according to the following reaction

Ni++ + 2OH- � Ni(OH)2

A two end-point acid-base titrationallows determination for boric acidand Ni content.



1M NaOH (1.0 mol/l or eq/l) (seeseparate note)

Distilled water


D-Mannitol 200 g/l in distilled wateror solid state D mannitol


Burette volume: 25 mlMaximum volume: See below

(working range)Stirring speed: 400 rpm

Working mode: pHNumber of end points: 2First end point: 6.80 pH (boric acid)Proportional band: 3.00 pHEnd point delay: 10 seconds

Second end point: 10.00 pH(nickel)Proportional band: 3.00 pHEnd point delay: 10 seconds

Stirring delay: 45 secondsMinimum speed: 0.4 ml/minMaximum speed: 6 ml/minSample unit: mlSample amount: 5Titration: Increasing pH

Results: differenceResult1: g/lCalculate with EP: 1Molar weight: 61.83 g/molCoefficients: 1 sample and 1 titrantResult2: g/lCalculate with EP: 2Molar weight: 58.69 g/molCoefficients:1 sample and 2 titrants

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Procedure

Calibrate the combined pH elec-trode using the 2 IUPAC standardsabove


Add 50 ml of the mannitol solutionor 10 g of solid-state D mannitol

If necessary add a few ml of dis-tilled water


Start method by pressing the RUNkey

Results

Generally expressed in g/l forboric acid and Ni content

Boric acidAs 1 mole of titrant reacts with1 mole of boric acid

R(Boric ac) = V(titr) * C(titr) * 61.83/ V(smp)

-V(titr) = total volume of titrant toreach the first end point in ml-V(smp) = Current sample amount-C(titr) = Exact concentration ofthe titrant in mol/l-61.83 = molecular weight of boricacid

Nickel contentAs 2 moles of titrant react with1 mole Ni++

R(Nickel) = V(titr) * C(titr) * 58.69/2* V(smp)

-V(titr) = volume of titrant usedbetween the first and the secondendpoint-V(smp) = Current sample amount-C(titr) = Exact concentration ofthe titrant in mol/l-58.69 = molecular weight ofNickel

Boric Acid and Nickel Content Determination

For results in g/lSettings indicated above for ENDPOINT TITRATION allow the Titra-tion Manager to give results ac-cording to the above formula.

3 determinations on the samebath

Boric acidMean: 44.40 g/l boric acidStandard deviation: 0.2 g/l boric acidRelative standard deviation: 0.45%

NickelMean: 65.90 g/l nickelStandard deviation: 0.66 g/l boric acidRelative standard deviation 1.0%

Notes

For this titration, the curve shapeis normally well defined, so endpoint determination is suitable.

Precipitation of Ni(OH)2 is not a

quick reaction so do not use toohigh a burette speed.

After D mannitol addition the pH ofthe sample is normally near by5.00 pH.

Sometimes it may be necessaryto heat the plating bath to 60°Cbefore pipetting just to dissolvethe precipitate.

Using a titrant with a lower con-centration (0.2 M or 0.5 M for ex-ample) can improve the accuracyof the results.

NaOH 1M, used as titrant, carbon-ates easily. Check the concentra-tion by means of a strong acid 1Mevery day if possible.

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Determination of Gastric Acidity

Introduction

The gastric secretions are a com-plex mix of HCl, pepsin, rennet,mineral chlorides (Na, K, Ca, Mg),calcium phosphate and organicmaterial (especially mucus). Gen-erally the acid concentration is0.1 N, for an healthy human, butthis concentration can be modifiedby many external factors as foodor drug ingestion or stress.In case of illness it can be neces-sary to determine the hyper-acidityor the acidity of the gastric secretion.

Principle

Acidity of gastric juice is deter-mined by an end-point titration atpH 7.00 using as titrant a NaOHsolution 0.1 equivalent/l. The sam-ple amount is generally between0.1 ml (100 µl) and 1 ml (1000 µl).The result is expressed as meq/ml( or eq/l).As for pathological situations, ex-pected results should be between0.01 meq/ml and may be up to 8meq/ml, it is very difficult to haveonly one titration method coveringthis whole range.

According to this fact the pre-programmed method "Gastricacidity" is suitable for orientationtest and 0.1-2 meq/ml range.Copying this method, it is possibleto create 2 others methods chang-ing only few parameters.

GASTRIC AC L(for 0.01-0.1 meq/ml range)Minimum speed: 0.02 ml/minMaximum speed: 0.5 ml/minSample amount: 500 µl

(possibly 1000µl)

GASTRIC AC H(for range > 2 meq/ml)Maximum volume: 20 mlMinimum speed: 0.1 ml/minMaximum speed: 5.0 ml/minSample amount: 100 µl

(possibly 200µl)


PHC3101 Combined pH electrode(E16M327) with CL114 (A94L114)cable

25 mm magnetic barrels A90A410

NaOH 0.1 equivalent/l solution in

distilled water (see separate appli-cation note but commerciallyavailable solution can be used).The pre-programmed titrant forthe method is labelled as "NaOHGastric 0.1"

pH standard IUPAC pH 4.005(S11M002) and pH 7.00 (S11M004)

Distilled or de-ionised water

Titration Vessel PP 22-45 ml904-489 (50 pcs) with specialholder 923-172 ( code number for10 pcs)

Pipettes for 100µl, 500µl and 1 ml

End Point titration settings(Gastric Acidity)

Burette volume: 10 mlMaximum volume: 40 mlStirring speed: 500 rpmWorking mode: pHNumber of end points: 1End point: 7.00 pHStirring delay: 10 secondsMinimum speed: 0.02 ml/minMaximum speed: 3.0 ml/minProportional band: 5.00 pHEnd point delay: 10 secondsSample unit: µl

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Sample amount: 1000(see working range)

pH: Increasing

Result 1: mlEquation unit: meq/mlEquation : V1*CT*1000/SA

Procedure

Put in place the pHC3101-9 com-bined electrode in the suitable holeof the electrode head (see Guideto bayonet accessories booklet)

Calibrate the combined glass elec-trode with the above mentionedbuffer solution

Place the electrode and the deliv-ery tip in opposite positions onelectrode head. The ends of elec-trode and delivery tip should be atthe same level in the beaker.

Install the titrant (NaOH gastric0.1N) and enter its concentration

Pour 20 ml of distilled or de-ionisedwater into the 22-45 ml beaker andplace it on the sample stand of theTitration Manager using a beakerholder

Add the recommended volume ofsample

If the expected result is approxi-mately known run the appropri-ate method

If the expected result is un-known, run, as orientation testwith 100µl of sample amount the"Gastric Acidity" method andaccording to this first resultchoose the suitable method

Working ranges

Titrant volume in ml as a function of the gastric acid concentra-tion (in meq/ml) and sample amount (in µl)

Results with "Gastric Acidity" and an healthy person

Used sample: 500 µl of a mix of HCl and pepsin in de-ionised waterThe result corresponds to:

R1 = V(titr) * C(titr) / V(smp)

V(titr) = Titrant volume in mlC(titr) = Titrant concentration in eq/lV(smp) = sample volume in ml

Results (3 determinations)Mean: 0.1067 meq/mlStandard deviation: 0.0004

Notes

1) The pHC3101-9 can be interesting for low maintenance level; Do notforget to store this electrode in KCl 3M solution as recommended byRadiometer Analytical. Note that this electrode is used in the pre-pro-grammed method.

2) Place the electrode and the delivery tip in opposite positions onelectrode head. Extremities of electrode and delivery tip are at thesame level in the beaker.

3) As the programmed time between two electrodes calibrations is 1day the corresponding icon on the main menu will always be "cloudy"after a calibration. See the user's guide (D21T043) chapter 2, p. 12.

4) For quick determinations, it is possible to use an end-point TitrationManager fitted with a 25 ml burette cylinder, 1000 µl of sample volumeand the pre-programmed method without change. With these conditionsthe working range is 0.02 meq/ml - 4.0 meq/ml.

Determination of Gastric Acidity

0.01 meq/ml 0.1 meq/ml 1.0 meq/ml 2.0 meq/ml 8.0 meq/ml

100µl (0.01 ml) (0.1 ml) 1.0 ml 2.0 ml 8.0 ml500µl (0.05 ml) 0.5 ml 5.0 ml 10.0 ml (40.0 ml)

1000µl 0.1 ml 1.0 ml 10.0 ml (20.0 ml) (80.0 ml)

In brackets: titration case not recommended for good accuracy or for titrantconsumption , increase or decrease the sample size respectively.

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Acid Number of Petroleum Products(Potentiometric titration ASTM D664-95 reapproved 2001)

Introduction

This method is a determination ofthe acidic components of a petro-leum product. The titration is runin non-aqueous media using po-tassium hydroxide in alcoholicsolution as titrant. Standard ASTMD664-95 recommends to use EndPoint titration technique when theInflection Point yields an ill-definedIP. As this application note alsoworks in end point titration, itshould be used if the inflectionmethod does not produce an ap-parent inflection (see also applica-tion note TTIP01.01PET).

Principle

The end point titration takes intoaccount the total volume of titrantnecessary to reach a potentialequal to that of a non-aqueousbasic buffer solution.

The result is expressed as mg ofpotassium hydroxide necessary totitrate 1 g of product.

The titrant concentration is 0.1Mand the molar weight of KOH is56.11 g/mol


As the titration occurs in non-aqueous media, it is recommendedto work with separate electrodesand a three-electrode system (seeelectrode maintenance andstorage notes).

pHG311 Glass Electrode (part no.E11M004) with a CL114 cable(part no. A94L114) as measuringelectrode

REF361 Reference Electrode(part no. E21M003) filled with LiCl1M in isopropyl alcohol as refer-ence electrode

M241Pt Metal Electrode (part no.E31M001) as cell groundingKOH 0.1M in isopropyl alcohol:Add 6 g of KOH to approximately1000 ml of isopropyl alcohol. Boilgently for 10 minutes. Leave thesolution to stand stay for 2 days,filter, store in a chemically resist-ant bottle and standardise versuspotassium hydrogen phthalate.This titrant is also commerciallyavailable.

Titration solvent:Mix 5 ml of distilled water with495 ml of isopropyl alcohol, thenadd 500 ml of toluene

Basic buffer solution (stock solu-tion):Weigh 27.8 of m-nitrophenol, add100 ml of isopropyl alcohol and500 ml of KOH 0.1M (in isopropylalcohol), dilute to 1000 ml withisopropyl alcohol, in a volumetricflask.Store the solution in a brown glassbottle.Use this solution within 2 weeksPrepare the basic buffer solutionby dilution of 10 ml of the stocksolution in 100 ml of titration sol-vent. Use this solution within1 hour (solution A).

Filling solution for the referenceelectrode:Dissolve 4.2 g of LiCl in 100 ml ofisopropyl alcohol

Buffer solutions pH 4.00 (S11M012)and pH 10.00 (S11M014)

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For strong acid number determi-nationAcid buffer solution:Weigh 24.2 g of 2.4.6-trimethyl-pyridine, add 750 ml of 0.2 mol/lHCl in isopropyl alcohol and diluteto 1000 ml with isopropyl alcoholusing a volumetric flask. Use thissolution within 2 weeks.Prepare the acid buffer solution bydilution of 10 ml of the stock solu-tion in 100 ml of titration solvent.Use this solution within 1 hour(solution B).

Warning: Reagents used in thisapplication note are flammable,cause severe burns and are haz-ardous if swallowed, inhaled orcome into contact with the skin oreyes. Use these reagents accord-ing to the safety regulations inapplication in the lab; also refer toASTM D664.


Cell grounding: M241PtMeasure: mVBlank: YESStirring speed: 550 rpm

Stirring delay: 30 sBurette volume: 10 mlMaximum volume: 10 mlNumber of end points: 2

Stirring delay: 30 secondsMinimum speed: 0.2 ml/minMaximum speed: 1 ml/min

End point 1: 200 mV (see notes)Proportional band: 200 mVEnd point delay: 10 secondsEnd point 2: -140 mV (see notes)Proportional band: 200 mVEnd point delay: 10 secondsDirection: Decreasing mV

Sample unit: gSample amount:see working range

Acid Number of Petroleum Products (Potentiometric titration ASTM D664-95 reapproved 2001)

Results by: cumulateNumber of results: 2

Result 1Result unit: mg/gMolar weight: 56.11Reaction: 1 smp + 1 titrCalculate with IP: 1Result 2Result unit: mg/gMolar weight: 56.11Reaction: 1 smp + 1 titrCalculate with IP: 2

Procedure

It is strongly recommended towork under a hoodPrepare the REF361 ReferenceElectrode for the first time.The REF361 is delivered filledwith aqueous KCl solution. Emptythis solution, rinse the electrodewith isopropyl alcohol and fill itwith the LiCl solution in isopropylalcohol.

Check electrode behaviour:Measure the potential indicated bythe electrodes dipped in solution Aand solution B. The potential isnormally close to -140/-160 mVfor solution A and around 200 mVfor solution B with the above-men-tioned electrodes. Enter thesevalues as end point values.For this, use the ELECTRODESand "DISPLAY MEASUREMENT"icons.Run a blank determination using125 ml of titration solvent.

Prepare the sample by diluting thenecessary amount of product in125 ml of titration solvent (seeworking range notes).Dip electrodes and delivery tip insolution.Wait for the stability of the startingpotential using the ELECTRODEand "DISPLAY MEASUREMENT"icon.

Run the titration

Electrode maintenanceand storage

a) After a titration, rinse the elec-trodes with titration solvent, thenwith ethyl alcohol and distilledwater and dip them in the pH 4.00buffer solution for 30/60 seconds.

b) After a cycle corresponding to5/10 titrations, change the meas-uring electrode. Clean it with titra-tion solvent, ethyl alcohol anddistilled water and store it in pH4.00 buffer solution.

c) Every morning or before start-ing a new titration cycle, check theelectrode system. Measure thepotentials reached by the elec-trodes dipped in pH 4.00 and thenin pH 10.0 buffer solutions. Thedifference between the two meas-urements should be at least 330 mV.

d) Once a week, clean the glasselectrode using the RadiometerAnalytical GK ANNEX Mainte-nance Kit (part no. S91M001).

Results

As indicated before results areexpressed as mg/g of KOH:

R(mg/g) = (Vtitr - Vblk) * C(titr) * 56.11 / W(smp)

Vtitr

= Total volume of titrant usedin ml

Vblk

= Blank volume used for solventtitration

C(titr) = Concentration of titrant inmol/l

W(smp) = Sample weight in g56.11 = molecular weight of KOH

As two end points are entered,if the petroleum product has nostrong acidity, the first resultwill be zero and the second theAcid Number of the product.

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Results with used engine oilMean: 2.5 mg/gStandard deviation: 0.05 mg/gRel. Standard dev.: 2%

Working range

Using the calculation formula for1 g of product and a 10 ml burette,the experimental range is between5 mg/g and 40 mg/g for the AcidNumber.In addition, ASTM D664 gives thefollowing for the sample size:

Notes

Note regarding the end pointvalues

The above-mentioned end pointvalues are experimental values,depending on reference andmeasuring electrode behaviourand also on the exact compositionof the titration solvent.

The first end point corresponds toStrong Acid Number and the sec-ond to Acid Number

Regularly check the measuredpotential by dipping the electrodesin the basic buffer solution (oracid buffer solution) and enter thisvalue as end point value.

Acid Number Mass of sample (in g)0,05-1 201,0-5,0 55,0-20 120-100 0,1

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Acid Number of Petroleum Products(Potentiometric titration ASTM D664-95 reapproved 2001)

Introduction

This method is a determination ofthe acidic components of a petro-leum product. The titration is runin non-aqueous media using po-tassium hydroxide in alcoholicsolution as titrant. If no inflectionpoint is detected during the titra-tion, an end point titration will benecessary (see application noteTTEP01.01PET).

Principle

The titration performs an inflectionpoint determination, taking intoaccount the total volume of titrantnecessary to detect an inflectionpoint at a potential close to that ofa non-aqueous basic buffer solution.The result is expressed as mg ofpotassium hydroxide necessary totitrate 1 g of product.The titrant concentration is 0.1Mand the molar weight of KOH is56.11 g/mol.


As the titration occurs in non-aqueous media, it is recommendedto work with separate electrodesand a three-electrode system (seeelectrode maintenance andstorage notes).

pHG311 Glass Electrode (partno. E11M004) with a CL114 cable(part no. A94L114) as measuringelectrode

REF361 Reference Electrode(part no. E21M003) filled with LiCl1M in isopropyl alcohol as refer-ence electrode

M241Pt Metal Electrode (partno. E31M001) as cell grounding

KOH 0.1M in isopropyl alcohol

Add 6 g of KOH to approximately1000 ml of isopropyl alcohol. Boilgently for 10 minutes. Allow thesolution to rest for 2 days, filter,store in a chemically resistantbottle and standardise versuspotassium hydrogen phthalate.

This titrant is also commerciallyavailable.

Titration solvent

Mix 5 ml of distilled water with495 ml of isopropyl alcohol, thenadd 500 ml of toluene.

Basic buffer solution (stock solu-tion)

Weigh 27.8 of m-nitrophenol, add100 ml of isopropyl alcohol and500 ml of KOH 0.1M (in isopropylalcohol), dilute to 1000 ml withisopropyl alcohol in a volumetricflask.

Store the solution in a brown glassbottle.

Use this solution within 2 weeks.

Prepare the basic buffer solutionby dilution of 10 ml of the stocksolution in 100 ml of titration sol-vent. Use this solution within 1hour (solution A).

Filling solution for the referenceelectrode

Dissolve 4.2 g of LiCl in 100 ml ofisopropyl alcohol.

Buffer solutions pH 4.00 (S11M012)and pH 10.00 (S11M014)

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For strong acid number determi-nation

Acid buffer solution

Weigh 24.2 g of 2.4.6-trimethyl-pyridine, add 750 ml of 0.2 mol/lHCl in isopropyl alcohol and diluteto 1000 ml with isopropyl alcoholusing a volumetric flask. Use thissolution within 2 weeks.

Prepare the acid buffer solution bydilution of 10 ml of the stock solu-tion in 100 ml of titration solvent.Use this solution within 1 hour(solution B).

Warning: Reagents used in thisapplication note are flammable.They can cause severe burns andare hazardous if swallowed,breathed or come into contact withthe skin or eyes. Always respectlaboratory health and safety regu-lations when using these reagents.Also refer to ASTM Standard D664.

Inflection Detectionsettings

CONTINUOUS ADDITION MODE(CONTINUOUS IP)

Cell grounding: M241PtMeasure: mVBlank: YESStirring speed: 550 rpm

Stirring delay: 30 sBurette volume: 10 mlMaximum volume: 5 ml (see notes)Stop point: -300 mVSmoothing parameter: 8Inflexion points number: 2Minimum speed: 0.05 ml/minMaximum speed: 1ml/minDirection: Decreasing mV

Inflection1: see notesMin. ordinate: -250 mVMax. ordinate: 60mV

Inflection 2Min. ordinate: -250 mVMax. ordinate: 60 mV


Results:Results by: cumulateNumber of results: 2

Result 1Result unit: mg/gMolar weight: 56.11Reaction: 1 smp + 1 titrCalculate with IP: 1Result 2Result unit: mg/gMolar weight: 56.11Reaction: 1 smp + 1 titrCalculate with IP: 2

INCREMENTAL MODE (DynamicIP)Speed: 5 ml/minDynamic dose: 12Maximum dose: 0.3 mlStability: 10 mV/minAcceptation: 00:30 min:sIP filter: 1IP reject: 15Others settings similar to Continu-ous IP

Procedure

It is strongly recommended towork under a hood.

When performing the applicationfor the first time, prepare theREF361 Reference Electrode.

The REF361 is delivered filledwith aqueous KCl solution, emptythis solution, rinse the electrodewith isopropyl alcohol and fill itwith the LiCl solution in isopropylalcohol.

Check the electrodes behaviour:

Measure the potential indicated bythe electrodes dipped in the solu-tion A and solution B. The potentialis normally close to -140/-160 mVfor solution A and around 200 mVfor solution B with the above-mentioned electrodes.


Use the icon ELECTRODES and"DISPLAY MEASUREMENT"

Run a blank determination using125 ml of titration solvent

Prepare the sample by dilution ofthe necessary amount of productin 125 ml of titration solvent (seenotes).

Run the titration.

Electrodes maintenanceand storage

a) When a titration is finished,rinse the electrodes with titrationsolvent, then with ethyl alcoholand distilled water and dip them inthe pH 4.00 buffer solution for30/60 seconds.

b) After a cycle corresponding to5/10 titrations, change the meas-uring glass electrode. Clean it withtitration solvent, ethyl alcohol anddistilled water and store it inpH 4.00 buffer solution.

c) Every morning or before start-ing a new titration cycle, check theelectrode system. Measure thepotentials reached by the elec-trodes dipped first in the pH 4.00and then in the pH 10.0 buffersolutions. The difference betweenthe two measurements should beat least 330 mV.

d) Once a week clean the glasselectrode using the RadiometerAnalytical GK ANNEX ElectrodeMaintenance Kit (part no. S91M001).

Results

As indicated before results areexpressed as mg/g of KOH

R(mg/g) =(Vtitr - Vblk) * C(titr) * 56.11 / W(smp)

Vtitr = Total volume of titrant usedin ml

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Vblk = Blank volume used forsolvent titration

C (titr) = Concentration of titrant inmol/l

W (smp) = Sample weight in g56.11 = molecular weight of KOH

Results with used motor oilMean: 2.8 mg/gStandard deviation: 0.05 mg/gRel. Standard dev. 2%

Working range

According to the calculation formulafor 1 g of product and a 10 ml bu-rette, the experimental range isbetween 5 mg/g and 40 mg/g forthe Acid Number.

In addition, ASTM Standard D664gives for the sample size:

Acid Number Sample weight(in g)

0.05-1 20 1.0-5.0 5 5.0-20 1

20-100 0.1


Notes

Note regarding the inflectionand the result numbersAs a general rule, with oils con-taining only weak acidic functions(Acid Number determination), onlyone inflection occurs during thetitration. A second inflection mayoccur (consequence of a noisytitration curve). If the curve param-eters are entered, 2 inflectionswith results by CUMULATE cangive the expected result even inthis situation.

Note regarding Strong AcidNumberMinimum and maximum ordinatesindicated for inflection point deter-mination are indicated for productswith Acid Number. For productswith Strong Acid Number, changethe first inflection as indicatedbelow:

Inflection 1Min. ordinate: 60 mVMax. ordinate: 200 mV

The indicated maximum ordinatecorresponds to the starting poten-tial of the solution.

Note regarding titrant stand-ardisationIf necessary, standardise the KOH0.1M in isopropyl alcohol againstweighed potassium acid phthalate(KOOC-C

6H

4-COOH with a molar

weight of 204.22 g/mol and 1 smp+ 1 titrant) and dissolved in CO

2free distilled water.

Note regarding the maximumvolumeDepending on the expected result,it may be necessary (especially incontinuous IP) to modify this set-ting. Try to enter a maximum vol-ume corresponding to 2 ml abovethe last inflection volume.Note that if the titration curve iswell defined, you can use the stopafter the last inflection point.

Titration Manager settings:

Inflection point number: 1Stop at last IP: YES(other settings similar to thoseindicated before)

Curve

mV

ml1 3

-80

-130

-180

542

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Acidity of Edible Oils(According to standard NF.EN.ISO 660-1999)

Introduction

In the edible oils industry, thedegree of acidity is an importantparameter for classifying the vari-ous oils. Acidity also has an influ-ence on the product taste. As thetitration is performed in non-aqueous media, it is recommendedto use a titration with inflectionpoint detection.

Principle

The sample is dissolved in methyl-isobutyl ketone (methyl4-pentanone2) and titrated with KOH(generally 0.1M) in isopropanol.The result is expressed as mg/g ofKOH for acid number and also asa % of oleic (or lauric or palmitic)acid (see results).


As the titration occurs in non-aqueous media, it is recommendedto work with separate electrodesand a three-electrode system (seeelectrode maintenance and stor-age notes).

pHG311 Glass Electrode (partno. E11M004) with a CL114 cable(part no. A94L114) as measuringelectrode

REF361 Reference Electrode (partno. E21M003) filled with LiCl 1M inisopropyl alcohol as referenceelectrode

M241Pt Metal Electrode (partno. E31M001) as cell grounding

KOH 0.1M in isopropyl alcohol astitrant solution

Add 6 g of KOH to approximately1000 ml of isopropyl alcohol. Boilgently for 10 minutes. Allow thesolution to rest for 2 days, filter,store in a chemically resistantbottle and standardise versus po-tassium hydrogen phthalate.

This titrant is also commerciallyavailable.

Ethyl alcohol as cleaning solutionfor the glass electrode

Titration solvent: methyl-isobutylketone (methyl4-pentanone2)

Filling solution for reference elec-trode: Dissolve 4.2 g of LiCl in100 ml of ethyl alcohol

Buffer solutions pH 4.00 (partno. S11M012) and pH 10.00 (partno. S11M014)

Warning: Reagents used in thisapplication note are flammable.They can cause severe burns andare hazardous if swallowed,breathed or come into contact withthe skin or eyes. Always respectlaboratory health and safety regu-lations when using these reagents.

Inflection Detectionsettings

CONTINUOUS ADDITION MODE(CONTINUOUS IP)

Cell grounding: M241PtMeasure: mVBlank: YESMin. ordinate: -185 mV (see notes)Max. ordinate: 100 mV

Stirring speed: 550 rpm

Stirring delay: 30 sBurette volume: 10 mlMaximum volume: 10 ml

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Stop point: -300 mVSmoothing parameter: 7Inflection point number: 1Minimum speed: 0.2 ml/minMaximum speed: 1 ml/minDirection: Decreasing mVStop at last IP: YES

Inflection1Min. ordinate: -220 mVMax. ordinate: -50 mV

Sample unit: gSample amount: see working range

Results:Number of results: 2

Result 1Result unit: mg/gMolar weight: 56.11Reaction: 1 smp + 1 titrCalculate with IP: 1

Result 2Result unit: %Molar weight: 282 (see results)Reaction: 1 smp + 1 titrCalculate with IP: 1

Procedure

It is strongly recommended towork under a hood.

When performing the application forthe first time, prepare the REF361Reference Electrode.

The REF361 is delivered filled withaqueous KCl solution, empty thissolution, rinse the electrode withisopropyl alcohol and fill it with theLiCl solution in isopropyl alcohol.

Weigh and dissolve the necessaryamount of sample in 50 ml of titra-tion solvent.

Dip electrodes and delivery tip inthe solution.

Run the titration.


a) When a titration is finished,rinse the electrodes with titrationsolvent, then with ethyl alcoholand distilled water and dip them inthe pH 4.00 buffer solution for 30/60 seconds. Before starting a newtitration rinse electrodes with ethylalcohol.

b) After a cycle corresponding to5/10 titrations, change the measur-ing glass electrode. Clean it withtitration solvent, ethyl alcohol anddistilled water and store it in pH4.00 buffer solution for one day.

c) Every morning or before startinga new titration cycle, check theelectrode system. Measure thepotentials reached by the elec-trodes dipped first in the pH 4.00and then in the pH 10.00 buffersolutions. The difference betweenthe two measurements should beat least 165 mV.

d) Once a week clean the glasselectrode using the RadiometerAnalytical GK ANNEX ElectrodeMaintenance Kit (part no.S91M001).

Acidity of Edible Oils (According to standard NF.EN.ISO 660-1999)

Results

As indicated before results can beexpressed in 2 different ways:

expressed as acid number inmg/g of KOH

R(mg/g) = Vtitr * Ctitr * 56.11/Wsmp


Ctitr = Concentration of titrant inmol/l

Wsmp = Sample weight in g

56.11 = molecular weight of KOH

expressed as acidity as a % ofacid

R (%) = Vtitr * Ctitr * M *100/1000 * Wsmp


Ctitr = Concentration of titrant inmol/l

Wsmp = Sample weight in g

M = Molar weight of organic acidused for result expression (seebelow)

Depending on the oil, three differ-ent organic acids are used forresult expression:

Results on olive oil (3 determin-ations)Acid numberMean: 0.5124 mg/gStandard deviation: 0.0056 mg/gAcidityMean: 0.275%Standard deviation: 0.0028%

Oil Acid Acid formula Molar Weight

Coconut oil Lauric acid CH3-(CH2)10-COOH 200 g/mol

Palm oil Palmitic acid CH3-(CH2)14-COOH 256 g/mol

Other oils Oleic acid CH3-(CH2)7-CH=CH-(CH2)7-COOH 282 g/mol

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Working range

Depending on the expected result,take a sample amount as indi-cated opposite:

Acidity of Edible Oils (According to standard NF.EN.ISO 660-1999)

Acid number (mg/g) Acidity (%) (*) Sample in g Titrant volume in ml (**)

<1 <0.5 20 <3.6

1-4 0.5-2 10 1.8-7.2

4-15 2-7.5 2.5 1.8-6.75

15-75 7.5-37.5 0.5 1.3-6.75

>75 >37.5 0.1 >1.35

(*) Calculated with oleic acid molar weight(**) For a 0.1M titrant

Notes

Note regarding ordinatesThe indicated values for the different ordinates areexperimentally measured using the above-mentionedelectrodes and methyl-isobutyl ketone as titrationsolvent. These values may change depending onelectrode behaviour (especially the reference elec-trode) and solvent quality.

Note regarding titrant standardisationIf necessary, standardise the KOH 0.1M in isopropylalcohol against weighed potassium acid phthalate(KOOC-C6H4-COOH with a molar weight of 204.22 g/moland 1smp + 1 titrant) and dissolved in CO2-free dis-tilled water.

Note regarding neutralisation of titration solventAs the titration solvent has a slight acid reaction it isnecessary to run a blank for every new batch of solvent.

Note regarding some particular oilsAs indicated in standard ISO 660-1999, some oils donot give detectable inflections. In this case, it is pos-sible to run an end point titration with an end pointvalue corresponding to the equivalent point of oleicacid dissolved in the titration solvent.Using the above-mentioned electrodes, this end pointvalue is close to -179 mV.

To determine this value, weigh around 100-120 mg ofpurified oleic acid and run a titration with KOH 0.1Min isopropyl alcohol as titrant solution.

mV

ml

0

-100

0.8 1.6 2.4 3.2

200

100

mV

ml

0

-200

1 2 3 4 5 6

mV

ml

0

-200

0.1 0.2 0.3 0.4 0.5 0.6

200

Curves

Blank

Olive oil

Oleic acid

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Carbon Dioxide in Wines

Introduction

Carbon dioxide (CO2) is generallypresent in wines. This is due tofermentation and the use of CO2for transfer operations duringwinemaking.The principle is to make the sam-ple strongly alkaline, by addingconcentrated sodium hydroxidesolution that converts all the CO2into CO3

2- and titrating with 0.1Mhydrochloric acid.

Principle

As the wine made strongly alkaline(pH10-12) contains only CO3

2-, thetitration occurs in two steps

CO32- + H+ HCO3

-

(end point at pH 8.6)

HCO3- + H+ CO2 + H2O

(end point at pH 4.0)

The end point titration is then per-formed with two successive endpoints (pH 8.6 and pH 4.0) and the

titrant volume delivered from pH 8.6to pH 4.0 is used to quantify theCO2 level in the wine in g/l. Themolar weight of CO2 is 44.0 g/mol.

A blank titration run with the same,but degassed, wine is necessary.



HCl 0.1 mol/l solution in distilledwater (see Application NoteTTEP01-01MIN)This solution is also commerciallyavailable.

NaOH 50% w/v in distilled water

Dilution of 50 g of NaOH pellets in100 ml of freshly boiled distilledwater is highly exothermic. Thesolution is also very caustic forthe skin and eyes. Observe labora-tory safety regulations.

Distilled water

In order to have a reproducibleblank result, use freshly boiled,distilled water which has beencooled to room temperature.



Burette volume: 25 mlStirring speed: 500 rpm

Working mode: pHBlank: YES (see notes)Predose: 0 ml (see notes)Stirring delay: 10 secondsMaximum volume: 40 mlMinimum speed: 0.2 ml/minMaximum speed: 10 ml/minDirection: Decreasing pH

Number of end points: 2End point 1: 8.6 pHProportional band: 2.0 pHEnd point delay: 5 secondsEnd point 2: 4.0 pHProportional band: 2.0 pHEnd point delay: 5 seconds

Sample unit: mlDilution: YESSample amount: 100Final dilution amount: 102 (see notes)Aliquot: 10

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ResultNo of results: 1Result by: differenceCalculate with EP: 2Result unit: g/lMolar weight: 44.0 g/molReaction: 1 smp + 1 titr

Procedure

Calibrate the combined pH electrodeLet the wine cool to 5°C

Blank preparationDegassing a wine sample.Pour the wine into a Buchner flaskand connect it to a vacuum systemfor 3 minutes.Degassing is also possible byheating the wine and boiling forfew seconds only. Then allow thewine to cool to room temperature.Pipette 100 ml of this degassedwine; add 2 ml or more of theNaOH 50% solution as accuratelyas possible. Make sure that the pHof this solution is around pH 10-12.Pipette 10 ml of this solution.Add the necessary volume of dis-tilled water; dip electrode and de-livery tip in the solution.Run a blank titration.You can run more than one test onthe blank; in this case the TitrationManager takes into account themean value.

Sample preparationTaking care not to lose carbondioxide, take 100 ml of the wine at5°C using a measuring tube.Pour it in a conical flask, add thesame volume of the NaOH 50%solution as for the blank, seal theflask and mix thoroughly.To avoid losing carbon dioxide,ensure that the flasks handlingthe sample are always at lowtemperature (near 0°C). Use anice bath or refrigerator.

Make sure that the pH of this solu-tion is around pH 10-12.Pipette 10 ml of this solution.Add the necessary volume of dis-tilled water, dip electrode and de-livery tip in the solution.Run the titration.

Results

Expressed as g/l of CO2 (molarweight of CO2 = 44 g/mol)

RCO2 = (Vtitr - Vblk) * Ctitr * 44 / Vsmp

Vtitr = Delivered titrant volumebetween pH 8.6 and pH 4.00 forsample

Vblk = Delivered titrant volumebetween pH 8.6 and pH 4.00 forblank

Ctitr = Titrant concentration in mol/l(generally 0.1)

Vsmp = Sample volume (generally10 ml)

The above-mentioned END POINTSETTINGS take in account:

- the blank calculation,- the dilution factor due to the addi-tion of 2 ml of NaOH 50% solution.

Result on red wineNo carbon dioxide measuredVerification of the method by addi-tion of Na2CO3 directly in the sam-ple beaker before titration with thesame wine.

Na2CO3 added in mg Vtitr - Vblk

24 2.57 ml

45 4.5 ml

61 6.08 ml

As indicated in this table themethod allows the added Na2CO3be measured with a recovery ratioclose to 98%.


Results on sparkling white wineSample dilution settings for thiswineSample amount: 50 mlFinal dilution amount: 52 mlAliquot: 10 ml

Blank on degassed wine5.37 ml of titrant (mean on 3determinations)

Results (3 determinations)Mean: 6.83 g/l CO2Standard deviation: 0.02 g/l CO2

Working range

According to the formula men-tioned under "Results":

1 ml for (Vtitr - Vblk) correspondsto 0.44 g/l of CO2

Note that this result is calculatedfor 10 ml of sample and does nottake into account the dilution factordue to addition of NaOH 50%solution.

Notes

Note regarding the "blank"As the behaviour of every wine isdifferent, it is necessary to run ablank titration for every differenttype of wine.

As the blank titration depends onthe composition of the studiedwine, do not forget to use thesame sample amount of wine anddilution settings for the blank de-termination and for the sample.

Note regarding the "predose"To save time it is possible to usethe "predose" function of the Titra-tion Manager.

Bear in mind that the "predose"volume of titrant is effective duringsample titration and also "blanktitration.

Note that using "predose" caneliminate the first end point.

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Note regarding the final amountdilutionThis amount is the sum of thevolume sample (generally 100 ml)and the volume of the NaOH 50%solution added (in this applicationnote 2 ml).

The volume of the NaOH 50% canchange according to the wine.

Note regarding the resultAs the method itself offers goodreproducibility, the accuracy of theresult depends on the handling ofthe non-degassed sample. It isimportant to avoid losing carbondioxide especially with sparklingwines.

Ensure that a sufficient volume ofNaOH 50% solution is added.

Bibliography

Techniques for chemical analysisand quality monitoring during wine-making

Ed: Patrick ILAND wine promotionCampbelltown AUSTRALIA

Curves

pH

ml

10

7

5 10 15 20 25

pH

ml

8

6

5 10 15 20 25

10

Blank

Sample: sparkling wine

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Base Number of Petroleum Products(Perchloric acid titration ASTM D 2896-01 and ISO 3771)

Introduction

The Base Number determinationis a measurement of the basicconstituents of petroleum prod-ucts. This titration uses perchloricacid in glacial acetic acid as titrantin a specific non-aqueous media.

Principle

The titration performs an inflectionpoint determination taking intoaccount the total volume of titrantnecessary to detect an inflectionpoint.The result is expressed as mg ofpotassium hydroxide for 1 g ofproduct.The titrant concentration is 0.1Mand the molar weight of KOH is56.11 g/molIf the titration curve is poorly de-fined with no inflection point de-tected, it is necessary to run aback titration (see "back titra-tion" note).


As the titration occurs in non-aqueous media, it is recom-mended to work with separateelectrodes and a three-electrodesystem (see electrode mainte-nance and storage notes).

pHG311 Glass Electrode (partno.E11M004) with a CL114 cable(part no. A94L114) as measuringelectrode,REF451 (part no. E21M005) withsalt bridge filled with saturatedNaClO4 in glacial acetic acid witha CL114 cable (part no. A94L114)as reference electrode (see Ref-erence electrode note),M241Pt Metal Electrode (part no.E31M001) as cell grounding.

Titration solventAdd one volume of glacial aceticacid to two volumes ofchlorobenzene.

Sodium perchlorate electrolytePrepare a saturated solution ofsodium perchlorate (NaClO4) inglacial acetic acid.

HClO4 0.1M in CH3COOHMix 8.5 ml of 70 to 72% HClO4with 500 ml of glacial acetic acidand 30 ml of acetic anhydride anddilute to 1000 ml with glacial ace-tic acid.Standardise the solution usingpotassium hydrogen phthalate(see standardisation note).This solution is also commerciallyavailable.

pH 4.00 buffer solution (partno. S11M012) and pH 10.00 buffersolution (part no. S11M014)

Warning: Some reagents used inthis application note are flamma-ble. Others can cause severeburns and are hazardous if swal-lowed, breathed or come into con-tact with skin or eyes. Always re-spect laboratory health and safetyregulations when using these rea-gents. Also refer to the ASTMD2896-01.

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Inflection DetectionSettings

CONTINUOUS ADDITION MODE(CONTINUOUS IP)Cell grounding: M241PtBurette volume: 25 ml

Measure: mVBlank: YESMin. ordinate: 400 mV

(see "ordinates" note)Max. ordinate: 700 mV

Stirring speed: 600 rpmStirring delay: 30 sMaximum volume: 15 ml

(see "maximum volume" note)

Stop point: 750 mV(see "ordinates" note)

Direction: Increasing mVMinimum speed: 0.1 ml/minMaximum speed: 1 ml/minSmoothing parameter: 5

Inflection points number: 1Inflection1Min. ordinate: 400 mV

(see "ordinates" note)Max. ordinate: 700 mVStop at last IP: YES


ResultsNumber of results: 1

Result unit: mg/gMolar weight: 56.11Reaction: 1 smp + 1 titr

Procedure (using 120 mlof titration solvent)

It is strongly recommended towork under a hood

For the first use, prepare theREF451 Reference Electrode.

The REF451 is delivered with thesalt bridge filled with aqueous KClsolution, empty this solution, thenrinse the bridge with water thenwith acetic acid and fill it with the

Base Number of Petroleum Products (Perchloric acid titration ASTM D 2896-01 and ISO 3771)

saturated solution of sodiumperchlorate (NaClO4) in glacialacetic acid.

Check the electrode behaviour:Measure the potentials reachedby the electrodes dipped in thepH 4.00 and then in the pH 10.0buffer solutions. The differencebetween the two measurementsshould be at least 330 mV.

For this, use the ELECTRODESand "DISPLAY MEASUREMENT"icon.

Run a blank determination using120 ml of titration solvent.

Prepare the sample by dilution ofthe necessary amount of productin 120 ml of titration solvent.

Run the titration.

Results

As indicated before, results areexpressed as mg/g of KOH

R(mg/g) = (Vt - Vb) * Ct * 56.11 /W

Vt = Total volume of titrant used in ml

Vb = Blank volume used for solventtitration

Ct = Concentration of titrant in mol/l

W = Sample weight in g

56.11 = molecular weight of KOH

Results on 2 different oil samples

Blank volume for solvent0.087 mlOil 1Mean on 2 testsTBN: 11.16 ±0.025 mg/gOil 2Mean on 2 testsTBN: 13.20 ±0.07 mg/g

Working range

According to the calculation for-mula for 1 g of product and usinga 25 ml burette, the experimental

range is between 5 mg/g and110 mg/g for the Base Number.

In addition, ASTM D2896-01 givesfor the sample size diluted with120 ml of solvent

Sample weight in g Expected Base No.

10-20 2.8-1.4

5-10 5.6-2.8

1-5 28-5.6

0.25-1 112-28

0.1-0.25 280-112

This table corresponds to an ap-proximate titrant volume of 5.0 ml


a) When a titration is finished,rinse the electrodes with titrationsolvent, then with distilled waterand dip them in the pH 4.00 buffersolution for 30/60 seconds. Beforestarting a new experiment, rinseelectrodes with titration solvent.Depending on the oil, it is possibleto use another solvent instead ofthe titration solvent.

b) After a cycle corresponding to5/10 titrations, change the meas-uring glass electrode. Clean it withtitration solvent, ethyl alcohol anddistilled water and store it inpH 4.00 buffer solution.

c) Every morning or before start-ing a new titration cycle, check theelectrode system. Measure thepotentials reached by the elec-trodes dipped in the pH 4.00 andthen in the pH 10.0 buffer solu-tions. The difference between thetwo measurements should be atleast 330 mV.

d) Once a week, clean the glasselectrode using the RadiometerAnalytical GK ANNEX Mainte-nance Kit (part no. S91M001).

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Notes

Reference electrodeInstead of the REF451, it is possi-ble to use the REF361ReferenceElectrode (part no. E21M003)filled with LiCl 1M in isopropanol.Using this electrode, it is neces-sary to change the potential ordi-nates; as experimental values youcan note:

Stop point: 950 mVMin. ordinate: 700 mVMax. ordinate: 850 mV

Maximum volumeDepending on the expected result,it can be necessary to modify thissetting (especially in continuous IP).Enter a maximum volume corre-sponding to 2-3 ml above the lastinflection volume.

OrdinatesIndicated ordinate values areexperimental values with the men-tioned titration solvent and elec-trodes. If the reference electrodeor titration solvent are changed, itshould be necessary to modify thedifferent ordinate values.

Titrant standardisationIf necessary, standardise the titrantagainst weighed potassium hydro-gen phthalate (KOOC-C6H4-COOH with a molar weight of204.22 g/mol and 1 smp + 1 titrant).Take 0.1 g of potassium hydrogenphthalate weighed to the nearest0.1 mg. Dissolve it with care in20 ml of warm acetic acid, add40 ml of chlorobenzene, cool andtitrate.Carry out a blank titration on 20ml of acetic acid plus 40 ml ofchlorobenzene.

Back titrationIf no inflection point is visible dur-ing direct titration, it is necessaryto run a back titration to determinethe Base Number.

In this case, a known volume (inexcess) of 0.1M perchloric acid inacetic acid is added to the samplediluted in the solvent titration.The excess of perchloric acid isback titrated with sodium acetatein acetic acid as titrant.

0.1M sodium acetate solutionUsing a volumetric flask, dilute5.3 g of Na2CO3 (anhydrous so-dium carbonate) in 300 ml of ace-tic acid, after dissolution, com-plete to 1000 ml with acetic acid(the molar weight of Na2CO3 is106 g/mole and 1 mole of Na2CO3gives in acetic acid 2 moles ofCH3COONa).

Procedure according to the ASTMstandardUsing titration solvent as solvent,titrate a known volume ofperchloric acid (for example 8-10ml) with the sodium acetate solu-tion.Note the volume V1 of the sodiumacetate solution.Weigh no more than 5 g of prod-uct and add the same volume oftitration solvent and the samevolume of perchloric acid thatshould be in excess.Titrate the solution with the sodiumacetate solution, note the volumeV2 used.If Cac is the titrant concentrationand W the sample amount:

BN (mg/g) = ((V1-V2)*Cac*56.11)/W

mV

ml1 2

700

600

43 5

500

400

mV

ml3 6

600

9 12

400

Sample

Curves

Base Number of Petroleum Products (Perchloric acid titration ASTM D 2896-01 and ISO 3771)

ACID-BASE TITRATIONS Introduction

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