08_part 3

PART-Ill

MATERIALS AND METHODS

COMPOUNDS STUDIED AND THEIR PREPARATION

5.1 Introduction

5.2 Compounds studied 5.2 a Selection of compounds 5.2 b Purity of the compounds chosen

5.3 Purification of compounds

5.4 Preparation of liquid systems for the study

CHAPTERS

COMPOUNDS STUDIED AND THEIR PREPARATION

5.1 Introduction

The selection of chemicals for the study must be primarily based

on the literature survey. Those components which have not be studied in

ones field of interest are invariably chosen for the study. The chosen

compounds are to be purified to the maximum possible extend when the

study aimed at is quantitative. This chapter presents the deta~ls of

compound selection and the sample preparat~on.

5.2 Compounds studied

5.2 a Selection of compounds

The literature survey indicates that much work has been done on

the dipolar interaction and dielectric relaxation behaviour of the mixtures

of nitriles and phenols. Hence certain organic liquids and powders with

cyanide and hydroxyi groups were chosen for the present investigation.

The compounds chosen are acetonittile, benzmitrile and some of its

para substituted compounds, methanol and phenol and some of its

para substituted compounds. These polar organic compounds and the

required non-polar solvents listed in table 5.1 were procured from reputed

manufacturers.

Table 5.1 Details of the compounds procured for the present study

Code Compound Quality and manufacturer No.

Group-1 (polar) 1 .l Acetonitrile (CHsCN) AR, SD fine chemicals, India. 1.2 Benzonitrile (CsH5CN) Pure, Merck, Schuchardt,

Germany.

1.3 p-Tolunitrile (4-CH3 C8H4CN) Pure,Merdt, Schuchardt, Germany.

1.4 pChlorobenzonitrile (4-CICsH4CN) Pure, Merck, Schuchardt, Germany.

1.5 p-Aminobenzonitrile (4-NH2CBH4CN) Pure, Merck, Schuchardt, Germany.

1.6 p-Hydroxybenzonitrile(4-OHC6H4CN) Pure, Fluka Chemika, India. Group-2 (polar) 2.1 Methanol ('%OH) AR, Qualigens, Fine Chem.,

India.

2.2 Phenol (CeH50H) AR, Ad. Lab, Pond~cherry, India. 2.3 p- Cresol (4-CHsC6H4CN) AR, SD fine Chemicals, India 2.4 p- Chlorophenol (4-C1 CeH40H) AR, SD fine Chemicals, lndia 2.5 p- Nitrophenol (4-N02CeH40H) Extra pure, Loba-chemie, India.

Group-3 (non-polar) 3.1 Benzene (&Ha) AnalaR, BDH, E.merck, India. 3.2 1,4-Dioxane @-CHs02) Extra pure, E.rnerck, India.

5.2 b Punty of the wmpwnds chosen

Throughout the present study the solutions of nittiles and phonds

and their complexes in benmne and in 1 ,CDLoxane were prepared only

after ascertaining their purity.

Except acetonitrile, the other five nitriles (1.2 to 1.6 in group-1, in table 5.1), duly certified to be pure by the manufacturers themselves, were used as such without any further purification. Methanol, phenol,

pcresol and gchloro phenol and the non-polar solvents benzene and

1,4- dioxane were used only afler purification.

The compounds used as such from the packing had been tested

for their purity, (i) in the case of liquids, by determining their boiling points, densities and refractive indices and (ii) in the case of powders, by determining their melting points. The determined test values agreed well

with the literature* (table 5.2 ).

5.3 Purification of oompounds Acetonittile was purified by slow distillation over phosphorous

pentoxide (P205) twice and tb liquid boiling at 8082c was collected in air tight flasks.

Table 5.2. Tested (exp) and literature (lit)' values of boiling points, densities and melting points of the compounds not

puntied further. .. .. . ... . .- ..- . . .- - .- . . . . . . . ..

Code Compound Boll~na Dolnt ( O c ) densltv lam 05')

No. (ex$)) (ln)* (exp) (111)' 2.2 CeH50H 191.0 191.7 1.0000 1.0102

1.3 4-CHsCsH4CN 107.0 103-106 0.9800 0 9810

1.4 4-CI CeH4OH 220.5 220 1.3000 1.3060 . -. - - -

' Ract~cal orpenic chemisby (Vogel.A.1) and cRc Hand book of chemistry and 71" edn

Code Compound No. ( e ~ ) (lit)' 1.5 4-NHzCeH4CN 87.0 86.0

1.6 4-OHCsH4CN 114.0 113.0

2.5 4-NOzCsHdOH 116.0 114.0

Methand was also purified by double distillation over PtOs and

used soon while preparing the solutions.

Phend was distilled and collected at 182'~ in 50 ml. flasks. The

colwrless phenol crystallised immediately at room tempereture. Slightly

yellowish p-cnrol was also purified by distillation and at its boiling

temperature of 200c, the colourless Cresol was collected. It ~ o t solidified

on cooling.

Pink coloured p-chlorophenol was purified by distillation under

reduced pressure and the colourless liquid was collected at the boiling

temperature of 220c in small air tight flasks.

The AnalaR BDH benzene was purified by following the standard

procedure. Benzene was allowed to stand on anhydrous calcium chloride

for two days and then filtered. Then the filtered benzene was refluxed with

phosphorous pentoxide for six hours and distilled. Sodium was drawn in

wires in the distillate and red~stilled. Then benzene was collected at its

boiling point of 8Oocc.

l,&Dioxam was punfied by first refluxing over sodium for six

hours to remove any impurity of water and then fractionally distilled

through an efficient column to remove any acetal (b.p. 82.5"~). Finally 1,4- Dioxane was redistilled from sodium and collected at its boiling

temperature of 101.5c.

These purified compounds were checked exper~mentally by

verifying their densities and refractive indices (Table 5.3).

Table 5.3. Comparison of experimental (exp.) and literature* (lit.) values of density and refractive of the purified

compounds.

code-

No.

1.1

2 , l

2.2

2.3

2.4

3.1

3.2

Compound (exp) (lit)

CHsOH 0.7910 0.7914

- .- .. . .- -- ...

refractwe index

(exp) (Ilt) 1.3440 1.3442

1.3285 1.3288

1.3285 1.3288

1.5310 1.5312

1.5580 1.5579

1.5010 1.5579

1.4220 1.4224

5.4 Preparation of lqud systems for the study

The above listed (table 5.1) six -CsN bonded (1.1-1.6) and five

-OH bonded (2.1-2.5) compounds and their 12 different complexes in the 1:l ratio were used to prepare the dilute solutions in benzene and in 1,4-

dioxane (34 different systems) for investigation .

The liquid systems of different desired concentrations for the study

were prepared by weight at laboratory temperature. The methods of

investigation in the present dielectric study involved concentration

variation of dilute solutions, a suitable range of solute concentration in

apolar solvents ranged from 0.004 to 0.024 whv (using a top pan electronic digital balance, Anamad, Series Max. 7000, sensitivity * 0.001

gm). in steps of 0.004 was preferred for all the systems. The complexes in dilute solutions were also prepared by weight so as to have the same

set of concentrations.

For the electronic and infra-red spectral studies the solutions were

prepared suitably in the decimolar and millimolar ranges so as to observe

and locate the absorption peaks, if any.

CHAPTER- 6

EXPERIMENTAL METHODS ADOPTED

6.1 Introduction

6.2 Measurement of static dielectric constants 6.2 a LCR Bridge balance- heterodyne beat method 6.2.b Maintenance of desired constant temperatures 6.2 c Fabrication and standardisation of the dielectric cell 6.2 d Determination of static dielectric constants

6.3 Measurements for micro wave dielectric constants

6.3 a Poley's method 6.3 b Smyth's method 6.3 c Experimental arrangement and procedure

6.4 Measurement of optical dielectric constants

6.5 Determination of density

6.6 Determination of the coefficient of viscosity

6.7 Ultra-Violet and Visible spectral study

6.8 Infra-Red spectroscopic study

CHAPTER- 6

EXPERIMENTAL METHODS ADOPTED

6.1 lntmduction

In dielectric study many experimental methods are used The

different methods are based on d~fferent theoret~cal models and

experimental conditions. Also, the use of a particular method depends on

the nature of the dielectric medium. In the case of liquid dielectrics, the

methods for investigation are selected based on physicochemical

properties of liquids. However, there exist certain experimental limitations

in view of accuracy and reliability of the methods.

In the present investigation certain experimental methods

suitable for nitriles, phenols and their complexes were employed. The

liquid systems, experimental techniques and procedure for the

determination of static, visible and microwave dielectric parameters,

densities and viscosities for all the prepared systems are given in the

following sections.

6.2 Meesunment of static diektrk consfants

6.2 a LCR Biidge balance heterodyne beat method

The relative electric permittivity, often called the dielectr~c constant

of the medium is determined by measuring the capacltame of a

condenser holding the dielectric medium. The principle of measuring

capacitance is similar to that of measuring conductance using bridge

methods. The capacitance bridges containing two resistance arms and

two capacitance arms are the normally used bridges. A variable-precision

condenser connected in parallel with the dielectric cell is adjusted for an exact bridge balance. The balancing is achieved by the resonance or

heterodyne beat method.

In the present study an analogue L C R Bridge (fig. 6.1) (systronics, model-921, India.) was used, with a fabricated dielectric cell as the experimental condenser to hold the dielectric liquids. The variable

frequency across the adjustable precession condenser and the fixed frequency (1 KHz) were given to the X-Y plates of the oscilloscope to get the Lissajou's ellipse. The matching of the frequencies corresponding to the capacitance balance was obtained exactly at the sharp collapse of the

ellipse into a straight line. Even a very small variation in the dielectric

constant changed the capecitance of the dielectric cell and

instantaneously prompted the ellipse to appar from the straight line

trace. This was found more suitable for the determination of dielectric

constants of dilute solutions of different concentrations at diierent

temperatures.

6.2. b Maintenance of desired constant temperatures

In addition to the concentration variation, it was proposed to study

the effect of temperature variation on the dielectric behaviour. The

variation and maintenance of desired constant temperatures in the range

303 K to 333 K were achieved by regulated hot water circulation. A solid

state constant temperature controlled water bath (INSREF, India) fitted with a water pump was used for this purpose. The liquid cells for the

determination of static, micro wave and visible dielectric constants were

maintained at constant temperatures simultaneously. They were linked

together with the water bath through the pump for the uniform variation

and maintenance of constant temperatures. This arrangement (fig. 6.2) facilitated the simultaneous measurements for the three dielectric

constants at the same constant temperatures without any discrepancy.

The viscometer and the pyknometer were also kept immersed in the water

bath at the respective constant temperatures and the measurements were

made at a time. The temperatures at measuring points were carefully

monitored during measurements. The uncertainty in the maintenance of

constant temperatures was estimated to be i 0.05'~.

FIG. 6.2 TEE CONSTANT TEMPERATURE CONTROLLER ARRANGEMENT WlTE VISCOMETER

6.2 c Fabrication and standardisation of the dielectric cell

The dielectric cell enclosing a cylindrical condenser was

fabricated to hold the dielectric liquid. It was basically a condenser with

little loss at low frequency electric fields. The condenser was designed in

such away that its air capacitance was around 200 pico-farad. It was

made up ot stainless steel (height 45.6 mm) having an inner solid cylindrical electrode (diameter a=14.74 mm) and an outer cylindrical thin electrode (diameter b =15.O mm). The two electrodes were mounted co- axially with a uniform gap of 0.13 mm and kept well insulated from each

other using tightly fixed mica spacers. This cylindrical condenser was

housed in a close fitting glass container having hot water circulation

facility. The container filled with the solutions made the cylindrical

condenser completely immersed in the liquid without any air space. The

leads from the electrodes were connected to the bridge for capacitance

measurements. The uncertainty in the measurement of capacitance was

assessed to be tO.5 pi-farad.

The fabricated cell was tested and standardised for the

measurement of dielectric constants of dilute solutions. The capacitance

of the cell without (Cs) and with the standard liquids like

carbontetrachloride, cydohexane, benzene, 1,4dioxane and

chlorobenzene (Co) was measured at different constant temperatures. 69

Using the known stendard val~es'~'" of cb, the static dieledr~c constant

and C, the free space capacitance (calculated from the absolute permittivity of free space and measured condeneer dimenoions) the theoretical values of the cell apacitmms when it is filled with the

respective standard liquids were obtained. For a liquid of known &, the

measured CD should be equal to &times C, but it was found more due to

the added lead capacnance CL, i.e., CD = ~o C,,+ CL. Solving this equatiOn

for any two standard liquids C,, and CL were determined. The value of C,

agreed with the calculated value and the values of CL remained constant.

More the dielectric constant, more the capacitance of dielectric cell. The

dielectric constant of a solution is dependent on both the concentration

and temperature. The static dielectric constants of some standard non-

polar and less polar liquids were determined at temperatures 303, 313,

323 and 333 K The static dielednc constants ranging from 1 .O to 5.84

were used for the purpose of calibration. There was a good canparison

between the present observed and literature values (table 6.1). The straight line plots (fig 6.3) between the dielectric constants and their

r w v e capacitances mn drawn to obUn the slopes at mr r tn t

temperatures.

calibration gaph for the determination of static dielectric constant with pure standard liquids (table.6.1)

6 ,

Ea 3

Cl @f ) Fg.6.3 at 303 K. slope = 0.0078983

These straight line plots showed a perfect linear variation of

measured capacitance with the dielectric constant and temperature.

Though the slopes at different temperatures were approximately the

same, they were significant to the fourth place comparable with the order

of variation in the dielectric constants and the respective capacitance

values for the experimental non polar solvents. This procedure minimised

the uncertainty in the measurement of variation in the static dielectric

constants of the very dilute solutions subjected even to a little change in temperature

6.2.d Determination of static dielectric constants

The static dielectric constants of the solutions prepared with the

non-polar solvents had been established to be signif~cantly different from

those for the pure non polar solvents. The values for the solution were

either greater or less than the dielectric constants of the solvent used.

The static dielectric constant of any solution ~ 0 x 3 could be obtained at a

given temperature T, using the solvent filled capacitance (C&

(Table 6.2) and solution filled capacitances (C& from the relation

where x represents solutes of d~fferent concentration and (-)T is the

static dielectric constant corresponding to the solution either with

benzene or with 1,4dioxane as a solvent at a constant temperature T.

Hence the static dielectric constants of all the solutions (MI) for nitriles,

023 for phenols and ~arnfor nitrilephenol complexes) were determined by varying the concentration at different temperatures and the values are

used for the evaluation of other dielectric parameters (chapter-9). The uncertainty in the determination of static dielectric constant was

estimated to be k 0.01 %

6.3 Measurements for micm wave dielectric constants

The methods of measuring dielectric constants at micro-wave

frequencies have been classif~ed.into (i) resonance circuit methods, (ii) transmission methods, (iii) impedance bridge methods and (iv) free space

techniques. Hill et.al.' critically analysed the merits and demerits of the

above methods.

In the present study transmission line method using wave guide

technique has been employed. The instrument used for this purpose was

basically the one constructed by Robberts and Von ~ i p p e l ' ~ . ~oley"~and

Smyth et.al.'li have described transmission line methods for pure liquids

and solutions of polar liquids in non-polar solvents respectively.

Accordingly the miwo wave bench was modified to facilitate transmission

through the liquid filled wave guide (liquid dielectric cell).

6.3 a Poley's method

The method developed by Poley requires the determinat~on of

Voltage Standing Wave Ratios (VSWRs) at various liquid path lengths. When an electromagnetic wave travelling in a medium is reflected at a

plane boundary between the two media, the complex reflection coefficient

is & = eVi * , where 4 is the phase of the reflection coefficient IRd is

the amplitude of the reflection coefficient. The transmission or the in put

impedance & of the first medium can be written as,

where ZI IS the drarederlstlc Impedance of the frrst med~um

If the attenuatron of the first medlum IS neglected, the Inverse

stand~ng wave ratlo IS

From equatron 6 1 the reflect~on coeffrclent &at the boundary of the two

medla can be wrltten as

For the short clrcurted termrnat~on,

Zo = Z2 tanh (v~L) 6 4 where Zz, v d and L are respect~vely the character~st~c ~mpedance,

propagation constant and length of the second medrum

Hence, [(2) tanh (v.L)]-1

Ro= [(2 tanh (V.L)]+I From equatrons 6 2 and 6 5 the Inverse voltage stand~ng wave ratlo can

be wrltten as

[($I tanh (V,IL)]-I 1 - z [(+ I tanh (v~L)]+I I

- 8

P = [(+ tanh ( ~ 4 1 - 1 I+[ z [(* ) tanh ( V L ) ] + ~ I

This relation connecting p and L can not be easily solved.

If the standing wave ratio is plotted as a function of the length L of

the l~quid column, a curve is obtained. Th~s curve exhiblts successive

maxlma and minima tendlng towards a final value of p, for a l~qu~d

column. The distance between the successive minima is equal to LJ2.

Further, using a wave guide, the loss tangent tanA is given by

E" tanA = -

A significant quant~ty analogous to the free space loss tangent

where E' and E" are nothing but the real and imag~nary parts of the

complex permittivity. band )L, represent the free space and cut off wave

lengths of the microwave. It is possible to deduce the value of tan (612)

as

from the ratios of p values in the successive maxim, q the attenuation in

the dielectric, and pd = (2dh). Denoting the standing wave ratio in the m

Th, and n Th, maxima by p, and p, one can write to a very close

approximation

A tanh [m x tan 51 EE=

A pn tanh [nx tan T]

and

A .@!! = tanh [m x tan 21 Pm

These two relations can be used to draw a set of curves for .@!! and Dn

A A .@!! as a function of tan 5 from which tan 5 may be read for any given Pm

measured standing wave ratio. The data of Id2 and tan AL? are used to

get E' and E" values, whiq are respectively given by

and

A The values of tan ( 5 ) for the different ratios of p,,, and p, as calculated

from equation 6.10 are available in literature for the determination of E'

and E". The measured values of p are corrected for the wall losses

outs& the cell and the losses at the termination and at the- window. The

value of p is determined first at d = 0, say it is po. Then the corrected

value of p will be = p- - pc.

6.3 b Smyth's method

Srnyth et.al.'" have described a 'width at twice minimum' standing

wave ratio method of determining the dielectric constant and dielectric

loss of low loss liquids or the solutions of polar liquids in non-polar

solvents. For the short urwited termination of d~electric lengths of integral

multiples of k&!, the inverse vokage standing wave ratio is given by

pn = Zz tanh (n a w2) 6.14

where 22 = l& and k,, represents the wave length of the microwave in

the air medium wave guide. In the case of low loss liquids the attenuation

a offered by the medium is smell and the equation 6.14 can be modified

as

The experimentally measured value of p,will include a factor RSC to

account for short cirwiting plunger resistance and other losses, so

The loss factor Rsc may be eliminated by plotting several values of

Pmwrured VS n. Using the slope (dp ,,,,,d Idn) of the least square fil

graph, the value of can be computed,

The dielectric loss s" is given by

and the dielectric constant E' is given by

In the present study the slopes were found from the inverse

V.S.W.R. values (11 S,) and their least square fit straight line plots.

6.3 c Experimental arrangement and procedure

The experimental set up used in the present study for the

determination of microwave dielectric constant (E') and loss (E") of dilute solutions was based on the methods of Von Hippel and smyth4 with some

modifications. An X- band microwave bench assembled with precision

wave guide components manufactured by Vidyut Yantra Udyog,

Modinagar, India. was used. The schematic diagram (fig. 6.4) and a photograph (fig. 6.5) of the actual arrangement are illustrated.

81

micrometer canylng piunge~-*

mamtattenuator-

Fig.6.4 X-BAND MICROWAM: BENCH 9.83 GHz

The redangular wave guide bench m i s t e d of a microwave

source of K-27 Klystron capable of generating a miaowave power at 9.83

GHz, an isolator, a variable attenuator, direct reading frequency meter, a

slotted wave guide section and the dielectric cell. The slotted sedron in

the broad face to a m m o d a t e a tuneable probecarriage was connected

to the liquid dielectric wave guide cell through a wave guide detector

mount (tuneable) and 90%- plane wave guide bend. The liquid cell was fitted with the teflon ended movable plunger driven by a micrometer screw

gauge (0.Olmm). T h cell was provided with an wter water circulation jacket for maintaining constant temperatures. The sample length of solution taken in the cell could be adjusted using the movable plunger.

This rectangular X-band bench was powered to get a stable

microwave propagation. The Klystron was operated accordingly and the

signal was fed to the attenuator through the ferrite isolator. This isolator

allowed free passage of power only in the forward direction and strongly

attenuated the reverse waves. The microwave power was measured using

the crystal detectors. One in the variable attenuator movable on the

slotted section and the other in the fixed position on the detector mount..

The out put currents form the aystal detectors were respedrvely fed to

the Voltage Standing Wave Ratio(V.S.W.R) meter (solid statemodel

V.S411) for the measurements of Sn and a cathode ray oscilloscope for monitoring the stability and out put power of microwave. The plunger in

the cell was moved down to the bottom to touch the mica sheet used to

hold the liquid in the wave guide section of the cell. The mica sheet was

too thin to transmit and not to attenuate the microwave. The tuneable

probe is moved along the slotted section to locate the statlonary wave

minima and maxima correspondingly for the maximum and minimum

VSWRs. The same was achieved by properly adjusting the Klystron wrrent, repeller voltage, modulating frequency and the wave amplitude.

Then the probe was fixed at the first minimum position from the cell end

by observing a maximum VSWR.

The prepared solution was loaded to the cell and by moving the

plunger up the change in the VSWR between maxima and minima were

noted (after selecting suitable range). This indicated the transmission of microwave through the solution and reflection from the plunger forming a

stationary wave pattern. From the micrometer readings correspond~ng to

the successive maxima and the respective VSWRs were noted to

determine the band p,, values then E' and E" values were computed using

equations 6.19 and 6.18. For all the solutions at different temperatures

the microwave dielectric constants and losses (E',, E ' I~, E'D, ~ ' 1 2 5 and E",,

E " , ~ E*=, Et'(=) were determined and used for the evaluation of Higasi parameters. The uncertainty in determination of B' and E" was estimated

to be * 0.1 % and * 3% respectively.

6.4 Measurement of optical dielectric constants

Molar refraction is the inherent property of transparent liqulds

systems containing conjugate molecules The molar refraction arlses from the atomic and electronic group refract~ons. This physical property is

related to the index of optical refraction, an easily measurable constant

using refractometers.

In the present study an Abbe's refractometer (fig.6.6) (Mltal, Ind~a.) provided with the water circulation facility around the split prism was

used. The refractive indices (no) of all the prepared solutions by varying the concentration at different uxlstant temperatures were noted The

corresponding optical dielectric conslants (E, = nd) were determined ( E,I, for nitriles, Q for phenok and for the 1:l complexes of nitriles and

phenols in dilute solutions). The uncertainty in the fneasurement of refractive index was found to be 2 0.0005.

A thin waned capillary ended glass pyknometer (6.046 ml) was made and used to determine the density at different temperatures. The

pyknameter was St6fd8fdiised with double distilled water in the

temperature range of 303 - 333 K The pyknorneter filled with the

experimental solutions war, maintained et desired constant temperatures

for suff~cient time and the loss due to evaporation was rninimised. A semi

micro single pan balance was used for weighing. The error in the

determination of density was found to be * 0.0005 gm.cc.'.

6.6 Determination of the ooellCcient of visas@

A new type of viscometerl" (fig 6.7) was designed and employed for the determination of the viscosity coefficients especially the effect of

temperature on the viscous flcw beheviow. The viscometer was

standardised by estimating Reynold's number from the flow time

(k 0.001 s) of double distilled water in the temperature range 303-333 K The vixxKneter constants (5483.7, 5291.1, 4940.9 and 4750.7 g s-') et different constant temperatures (303, 31 3, 323 and 333 K) were evaluated for the determination of vismsity values. The applicability of this new

visameter was tested by determini- the viscosities of the standard

85

FIG. 6.7 THE MSCOMETER

srmple pure lrqurds like benzene, 1,4dloxane, carbon tetrachloride and

cychlohexane The vrscos~ty values agreed wrth !he lrterature The

vlscosltles of all the prepared solutrons at drfferent desrred constant

temperatures were measured usrng vrscometer (chapter-10)

6 7 Ultra-V!o/et and V~srble spectral study

A computer based Spectrophotometer (Electron~c Corporatron of lnd~a Lrmrted, model GS 5703-AT) was used for recordrng the electronrc spectra It IS a stable beem ratio recordrng type wrth a scannlng range

190-390 nm, accuracy +O 5 nm and a resolutron of 2 nm The dllute

solut~ons of the chosen systems were made up ~mmed~ately before scan

The l~qu~d samples were taken In 10 mm path length cuvettes wrth auto

select~on through computer The absorbance spectra were recorded

(chapter-9)

6 8 Infra-Red spectmscvplc study

Infra-Red spectroscoprc stud~es were carrred out using a Perkln

Elmer 1600 series Four~er Transform Infra-Red Spectrophotometer All

the chosen l~qu~d samples were prepared just before scan to record the

spectra. The samples were taken as thin films (thickness m O.Olmm or even less) squeezed between the two infra-red transparent windows (NaCI). The thickness of the films was adjusted to be almost same using squeeze plates of the sample holder. The spectra were acquired for the

entire range (chapter-9).