pH METER

Presenter:Presenter:

Dr S Kamalakar Dr S Kamalakar PuripandaPuripanda

DEPT OF SAMHITADEPT OF SAMHITA

SDMCA&HSDMCA&H

pH METERpH METER

The pH meter was invented in 1934 by the

American chemist Arnold O. Beckman (1900-2004) to measure the sourness of lemons

A simple and speedy device to measure the acidity and alkalinity of a fluid. A pH meter acts as a volt meter that measures the electrical potential difference between a pH electrode and a reference electrode and displays the result in terms of the pH value of the solution in which they are immersed.

INTRODUCTION

The logarithm of the reciprocal of hydrogen-

ion concentration in gram atoms per litre; provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution (where 7 is neutral and greater than 7 is more basic and less than 7 is more acidic);

pH(Potential of Hydrogen)

The formal definition of pH is the negative logarithm of the hydrogen ion activity.pH = -log[H+]

An acid can be defined as a proton donor, a chemical that increases the concentration of hydrogen ions in solution. HCL----------H+ + CL-

A corrosive liquid with a pH less than 7; a solution of in water of a substance that releases hydrogen ions

A base can be defined as a proton acceptor, a chemical that reduces the concentration of hydrogen ions in solution. KOH……..K+ + OH-

A corrosive liquid with a pH greater than 7; a solution of in water of a substance that releases hydroxyl ions

Acids and Bases

A pH measurement system consists ofHigh input meter2 probes Buffer powder/capsules for calibrationDistil water

pH Meter

Probe 2Probe 1

1.Glass electrode: It consists thin bulb of special glass blown(lithium) at the end of the glass tube,and the bulb is filled with

dilute acid for example decinormal HCL acid connected to a silver chloride electrode

2.Calomel electrode: It consists of a glass tube containing saturated KCL connected to

platinum wires through mercury (mercury chloride)

3.Reference junction: typically made of porous ceramic or porus teflon

Probe 1 consists of 3 parts (2 electrodes)

ELECTRODE: A conductor used to make electrical contact with some part of a circuit

Probe 1

1

2

3

Probe 2

CHECKING FOR SOLUTION’S TEMPERATURE

2 PROBES ARE CONNECTED TO HIGH

INPUT pH READING MTER

The act of checking or adjusting (by comparison with a standard)

the accuracy of a measuring instrument

BUFFER POWDER/CAPSULES

1.High input pH reading meter

A voltmeter in the probe measures the

difference between the voltages of the two electrodes.

The meter then translates the voltage difference into pH and displays it on the screen.

Before taking a pH measurement the meter must be calibrated using a solution of known pH.

pH Meter

Temperature compensation is connected

within the instrument because pH electrodes are temperature sensitive.

Temperature compensation only corrects for the change in the output of the electrode, not for the change in the actual solution.

Buffers are solutions that have constant pH values and the ability to resist changes in pH.

They are used to calibrate the pH meter.

Temperature and Buffers

1.The 2 probes should connect to pH reading meter Connect the power pack of 230v to the pH meter Dip the electrode in a standard solution of pH and set

the temparature and take reading(The 1st probe should be calibrate with different buffer

solutions for rule out the errors of the electrode(buffer solution:buffer powder + distil water).Then should check the solution temperature with 2nd probe)

Remove buffers wash and wipe the electrode and dip it in the desireble solution and take the reading.

METHOD OF USING

An electrical potencial devolops when one liquid is

brought into contact with another one ,but a membrane is needed to keep such liquid aparts

A ph meter measures essentially the electro – chemicall potencial between a known liquid inside the glass electrode and unknown liquid outside

Because the thin glass bulb allows mainly the agile and small hydrogen ions to interact with the glass,the glass electrode measures the electro chemical potential of hydrogen ions.

How a pH meter works

PH EXAMPLE

0 HCL

1 GASTRIC JUICES

2 LEMON JUICE

3 ORANGE JUICE

4 COLA

5 COFEE

6 RAIN WATER

7 PURE WATER

8 SEA WATER

9 BAKING SODA

10 ANTACIDS

12 DETERGENT

13 OVEN CLEANER

14 NAOH

SWEAT…4 -6 VAGINAL FLUIDS…..4.50 -5 SALIVA…..6.2 – 7.4 BLOOD……7.35 – 7.45 URINE…..MORNING 6.5 – 7,THEN 7.5 – 8.0 INTESTINAL FLUIDS….7.41 SEMEN….7.35 – 7.40 LYMPH …..7.4 – 9.0 EYE TEARS…7.1 – 7.4 PANCREATIC JUICES…..8.5

BODY FLUIDS

THANK U

REFERENCES:RESEARCH METHDOLOGY FOR AYURVEDIC SCHOLARS-

DR.S.SURESHBABUTABER’S CYCLOPEDIC MEDICAL DICTIONARY EDITION 20

INTERNETIMAGES COLLECTED FROM RASASHASTRA DEPT SDMCAH