Crystal growing has given new dimension to carry through the demand of modern engineering. Natural crystals are non available in equal measures and besides holding imperfectness and low pureness. Man-made crystals, prepared in the research lab can replace these natural crystals. These man-made crystals are pure holding less imperfectness and can be grown of desirable size.

With the aid of gel method a batch of work has been done [ 35 ] . Afterwards several research workers [ 73-85 ] have used gel method to turn assorted types of crystals and characterized it, besides due to its simpleness of the procedure it can be successfully used to turn the crystals at room temperature with good control over nucleation [ 14-19, 86-89 ] .

A batch of plants have been devoted in recent old ages to the readying of oxalates of metallic ion or mixture of metallic ions. Crystals of Ca oxalates were grown by gel method [ 47-48 ] . Gadolinium Sm oxalates were grown utilizing gel method [ 50 ] . Barium oxalate crystals were grown by gel technique [ 6, 7, 49, 90 ] , Na oxalate crystals [ 8 ] , Ce oxalate crystals [ 20 ] , La Nd oxalate individual crystals [ 21 ] , Cd oxalate individual crystals [ 51 ] were grown utilizing gel method. For acquiring full information about turning crystals, they are characterized by assorted techniques.

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In this work, the adult Sr oxalate crystals were characterized by

X-ray diffraction ( XRD )

Fourier Transform Infrared Spectroscopy ( FT-IR )

Thermal analysis

Thermal Gravimetric Analysis ( TGA )

Differential Thermal Analysis ( DTA )

Differential Scanning Calorimetry ( DSC )

Chemical Analysis

I ) Gravimetric

two ) Volumetric

5 ) Energy Dispersive Analysis by X-ray ( EDAX )

6 ) Scaning Electron Microscope ( SEM )

The present chapter describes growing of crystals of undoped Sr oxalate by set uping optimal conditions and their word picture.

3.2 Gel technique

The growing of crystal in the gel method is based on the diffusion of reactant in gel. Following two techniques for the procedure of diffusion in gel media were employed.

Single diffusion technique.

Double diffusion technique.

These techniques are discussed in chapter I and shown in fig. 1.1 and fig. 1.2.

Both techniques were used in the present work but individual diffusion technique was found most suited for the growing of good quality crystals in present work. Requirements and process of both techniques are discussed below.

3.3 Apparatus used

Corning glass trial tubing

Corning glass U form tubing

Magnetic scaremonger

Digital pH metre

Burette and pipette

Beaker, mensurating cylinder

Specific gravitation bottle, Electronic Balance

Gas for warming, funnel, base, glass rod, filter paper, wire gage, cotton stopper etc.

3.4 Chemical used

All are A.R. Grade as follows

Sodium Meta silicate ( Na2SiO3, 5H2O )

Strontium Chloride ( SrCl2, 6H2O )

Strontium Nitrate [ Sr ( NO3 ) 2 ]

Oxalic acid ( H2C2O4 )

Agar-agar pulverization

Double Distilled Water

3.5 Experimental process

The chemical reaction method is used to turn undoped Sr oxalate crystals. The technique involves turning of crystals by leting the reaction of two solutions of soluble salts by diffusion through a gel with subsequent nucleation and the crystal growing, which uninterrupted due to the gradual precipitation of indissoluble merchandise.

3.5.1 Chemical reaction

Strontium chloride reacts with oxalic acid and it forms strontium oxalate,

SrCl2 + H2C2O4 i‚® SrC2O4 + 2HCl

Strontium Nitrate reacts with oxalic acid and it forms strontium oxalate,

Sr ( NO3 ) 2 + H2C2O4 i‚® SrC2O4 + 2HNO3

3.5.2 Preparation of Silica gel

I ) Preparation of Na metasilicate solution

Sodium metasilicate solutions of different specific gravitation were prepared by adding proper sum of Na metasilicate in dual distilled H2O. This solution was continuously stirred for half an hr by utilizing magnetic scaremonger and filtered straight into the airtight coloured bottle.

II ) Preparation of silica gel from Na metasilicate

Silica gel was prepared by blending solution of Na metasilicate and oxalic acid which is one reactant of known concentration and so continuously stirred for 10 proceedingss utilizing magnetic scaremonger. To acquire good proper of gel assorted tests were made.

3.5.3 Single diffusion

In this process 12 milliliter of 0.5 M oxalic acerb solution was taken in a little beaker, in which Na meta silicate solution of 1.04 gm/cc was added bead by bead from burette and continuously stirring it by utilizing magnetic scaremonger for keeping the pH in the scope 3 to 4.5 of given solution and noted burette reading. Continuous Stirring is done to avoid the inordinate local ion concentration, which may otherwise cause premature gelling and do the concluding medium nonuniform and turbid. The solution was continuously stirred till the pH of the ensuing solution has reached a specific value. The crystallising vas were used basically consist of standard glass tubing of 2.5 centimeter inner diameter and 20 centimeter in length. Geling mixture, after observing pH was allowed to put in glass trial tubing. These tubings were hermitically sealed to forestall vaporization and taint of the open surface by dust atoms of ambiance or atmospheric drosss and were kept undisturbed.

The mixture appeared to be rather crystalline ab initio. However, with the oversight of clip, its coloring material changed and became milky white when the gel was wholly set. The gel was normally found to put 25 to 30 yearss, depending on the environmental temperature. After guaranting steadfast gel scene, it was kept for aging for 3 to 4 yearss. The ripening of the gel reduces the diameter of the capillaries in gel so that the velocity of the reaction is automatically controlled. After guaranting proper, house gelation, supernatant Sr chloride solution was introduced carefully over the set gel with the aid of pipette, the solution being allowed to fall along the wall of the trial tubing to forestall the gel surface from interrupting or checking. Again these tubings were hermitically sealed to forestall vaporization and taint of the open surface by dust atoms of ambiance or atmospheric drosss and were kept undisturbed. Tubes were once more unbroken idle for farther procedures to happen.

The supernatant solution started easy diffused into the gel medium. Nucleation was observed after 5 to 6 yearss and crystals started to turn. In silica gel really little crystals ( micro crystals ) were observed inside the gel medium. Though different concentration of reactant and supernatant were tried, but really little sized crystals were observed as shown in fig. 3.1.

3.6 Consequences and treatment

A series of experiments were conducted by changing the concentrations of inner and other reactants every bit good as the pH of the medium, gel denseness, gel puting clip and gel ageing clip. In individual diffusion, after a few yearss better quality, good reflecting, crystalline micro crystals were observed as shown in fig. 3.1.

3.6.1 Optimum conditions

I ) Density of Na meta silicate solution — 1.04 gm/cc

two ) Volume of Na meta silicate solution — 20.2 milliliter

three ) Volume of 0.5M oxalic acerb solution — 12 milliliter

four ) pH of gel — 4.0

V ) Concentration of supernatant, Sr chloride — 1 Meter

six ) Room Temperature — 30oC

seven ) Gel puting period — 25 yearss

eight ) Gel aging period — 4 yearss

nine ) Growth period — 70 yearss

ten ) Quality of crystals — Micro crystals

3.6.2 Effect of assorted parametric quantities on crystal growing

I ) Different densenesss of silicon oxide gel

Different densenesss of Silica gel from 1.02 to 1.06 gm/cc were tried. It was observed that, higher densenesss gel set more quickly than the lower densenesss. Besides the transparence of gel decreased as the denseness increased. The good consequences were obtained with the gel denseness 1.04 gm/cc. Low denseness gel could non put in needed period and found to be unsuitable for diffusion of reactants. Pore size of gel was reduced with denser gel, thereby decreased nucleation denseness ; this is good agreed with the decision [ 35 ] .

II ) Concentration of reactant

Different concentrations of reactant oxalic acid 0.3 M to 1 M were used. The good consequence was obtained with 0.5 M concentration of reactant, oxalic acid which is used for puting of gel every bit good as one of the responding constituent. Different concentrations of Sr chloride or Sr nitrate were besides tried and the optimal value of the same are mentioned.

III ) pH of gel

The consequence of pH of silicon oxide gel was studied utilizing different ratios of Na meta silicate and oxalic acid in the mixture of silicon oxide gel. As the comparative measure of Na meta silicate was increased in the mixture, pH values were increased and leaded to hapless formation of crystals. However at low pH values the crystals were non formed in the gel. pH values 3 to 4.2 were tried, it was observed that below 3.5 pH the gel was non set wholly while above 4 pH the gel was set but the transparence of the gel was decreased. Therefore pH was kept 3.5 to 4. It was observed that good consequences were obtained at 4 pH. It had been found that when pH was low in the scope of 3 to 4 it took long clip about four hebdomads to put the gel wholly and it took more than one month to add the supernatant. With this long clip of puting and aging the gel was got shrinked and the outer surface of the gel in the trial tubing which works as an interface for the diffusion of supernatant becomes wholly uneven and the tallness of the gel column is much reduced because of gel shriveling. To avoid this trouble and to acquire sufficient tallness of gel column and to acquire better quality crystals below 3cm deepness of the gel column, experiment repeated with initial more tallness of the gel column that means somewhat more than half of the tallness of the trial tubing. But this procedure once more leads to growing of really little crystals.

Therefore to acquire better quality crystals another media of gel that means agar- agar gel was employed to turn the crystals. Barium oxalate crystals were grown in agar-agar gel to acquire better quality crystals [ 6, 7 ] .

3.7 Preparation of Agar-agar Gel

Agar-agar gel was prepared by fade outing 1 to 3 gram of agar-agar pulverization into 100 milliliters hot double distilled H2O to acquire homogeneous solution. This solution was so poured into the trial tubing with one reactant and kept for puting gel by covering the oral cavity of the trial tubing with cotton stopper. After puting gel, it was kept for aging.

3.7.1 Experimental Procedure

1 to 5 gram of agar-agar pulverization was dissolved in to hot dual distilled H2O mixed with 0.5 M to 1 M oxalic acerb solution. The crystallising vas were used basically consist of standard glass tubing of 2.5 centimeter inner diameter and 20 centimeter in length. Geling mixture poured in glass trial tubing. These tubings were hermitically sealed to forestall vaporization and taint of the open surface by dust atoms of ambiance or atmospheric drosss and were kept undisturbed. The gel was normally found to put 3 to 4 yearss, depending on the environmental temperature. It was observed that the mixture in a glass tubing was ab initio crystalline and easy turned light yellowish. The H2O easy evaporated and gel was wholly set. After guaranting steadfast gel scene, it was kept for aging for 3 to 4 yearss. After that 0.5 M to 1 M solution of Sr chloride or Sr nitrate was added as a supernatant over the set get. Nucleation was observed after 5 to 6 yearss and crystals started to turn. It was observed that for 1 gram, 2 gm agar-agar pulverization and with 2 milliliters, 3 ml solution of 0.5 M to 1M oxalic acid, the gel did non put wholly within specific clip and so by adding supernatant proper reaction could non take topographic point and no formation of crystals.

Solutions prepared with 3 grams to 5 gram of agar-agar pulverization and with 2.5 milliliters to 3 ml solution of 0.5 M to 1 M oxalic acid, the gel could put wholly but after adding supernatant the rate of diffusion was slow. Due to decelerate rate of diffusion nucleation formation was found to be slow and hence really few karyons were nucleated. Therefore to avoid this job the reactant and supernatant were interchanged.

By substituting the reactant and supernatant in the above individual diffusion method good expected consequences were obtained. Hempen growing, crowded and opaque, bantam but bright and stray crystals were obtained in the gel, as shown in fig. 3.2.

3.8 Consequences and treatment

A series of experiments were conducted by changing the concentrations of inner and other reactants every bit good as gel scene clip and gel ageing clip. In individual diffusion, after a few yearss ‘ better quality, hempen growing, crowded and opaque, bantam but bright and stray crystals were obtained in the gel, as shown in fig. 3.2.

3.8.1 Optimum conditions

I ) Concentration of agar Gel — 3 %

two ) Concentration of reactant, Sr chloride — 1 Meter

three ) Concentration of supernatant, oxalic acid — 1 Meter

four ) Room temperature — 30oC

V ) Gel puting period — 4 yearss

six ) Gel aging period — 2 yearss

seven ) Growth period — 30-45 yearss

nine ) Quality of crystals — 1mm ten 1mm

( about ) isolated

Crystal

To acquire better quality crystals another technique that means dual diffusion

with agar- agar gel was employed to turn the crystals.

3.9 Double diffusion

3.9.1 Experimental process

3 % of agar-agar pulverization was added in hot dual distilled H2O with uninterrupted stirring to acquire homogenous mixture and so this solution was poured in corning glass U – tubing of diameter 2.5 centimeter up to allow tallness. These tubings were hermitically sealed to forestall vaporization and taint of the open surface by dust atoms of ambiance or atmospheric drosss and were kept undisturbed for gel scene and aging. The gel was normally found to put 3 to 4 yearss, depending on the environmental temperature. It was observed that the mixture in a glass tubing was ab initio crystalline and easy turned light yellowish. The H2O easy evaporated and gel was wholly set. After guaranting steadfast gel scene, it was kept for aging for 2 to 3 yearss. After aging, Sr chloride and oxalic acid were added into two limbs of the U-tube simultaneously of the same tallness. After 4 to 6 yearss really few reflecting really few micro crystals were nucleated near to the oxalic acerb side and so the nucleation of the crystals started distributing from oxalic acerb side to strontium chloride side in the U-tube. It had been besides observed that as the crystal nucleated towards the Sr chloride side, the size of the crystals had been somewhat increased.

As the crystal ab initio nucleated at the oxalic acerb side instead than the Centre of the U-tube, this indicates that the rate of diffusion of oxalic acid in the agar-agar gel was less than the Sr chloride. Therefore really few micro crystals were obtained in the gel as shown in fig. 3.3.

3.10 Consequences and treatment

A series of experiments were conducted by changing the concentrations of inner and other reactants every bit good as gel scene clip and gel ageing clip. In dual diffusion, after a few yearss ‘ really few micro crystals were obtained in the gel as shown in fig. 3.3.

3.10.1 Optimum Conditionss

I ) Concentration of agar-agar gel — 3 %

two ) Concentration of reactant I, Sr chloride — 1 Meter

three ) Concentration of reactant II, oxalic acid — 1 Meter

four ) Room temperature — 30oC

V ) Gel puting period — 4 yearss

six ) Gel aging period — 2 yearss

seven ) Growth period — 30 yearss

nine ) Quality of crystals — Very few micro crystals

3.11 Effect of assorted parametric quantities on crystal growing

Different parametric quantities such as nucleation, concentration of reactant, aging period of gel etc. have considerable consequence on the growing rate of crystals. These parametric quantities are discussed as follows.

I ) Nucleation

In individual diffusion it was observed that the rate of nucleation depends upon concentration of supernatant solution. It was found that at dilute solution, the rate of nucleation was slow and size of it was besides little. Under these conditions really few karyons were nucleated. However, on increasing the concentration of supernatant, the rate of nucleation and growing of nucleation was besides big. This indicated fluctuation of figure of karyons formed with regard to alter in concentration of supernatant.

In individual diffusion, at 1M concentration of supernatant, bantam, bright and reflecting stray crystals were grown in the agar-agar gel.

In dual diffusion it was observed that by changing the concentration of both the reactants, the rate of diffusion through the agar gel was changed. As a consequence rate of nucleation and size of crystals was besides affected.

II ) Effect of concentration of agar gel

It was observed that the transparence of the gel was decreased as the concentration of gel was increased and coloring material was changed to yellowish. It was besides observed that

I ) really little size and few crystals were obtained utilizing strontium chloride as a supernatant while

two ) good quality, big size and more crystals were obtained in the same concentration and same conditions utilizing oxalic acid as a supernatant, which suggested oxalic acid to be used as supernatant.

III ) Effect of aging period in agar gel

More ageing period reduces the figure of turning karyon. This might be due to decrease of cell size and accordingly the rate of diffusion of supernatant into gel. Good quality and big size crystals were obtained at moderate aging period of gel about a hebdomad.

3.12 Word picture

3.12.1 X-ray Diffraction ( XRD )

X-ray diffractogram is utile in the analysis of crystal construction. Cell parametric quantities, ‘d ‘ values, unit cell, volume and lattice system etc. can be evaluated by utilizing x-ray diffractogram.

X-ray diffractogram of gel grown undoped strontium oxalate crystals were recorded utilizing pulverization rotated diffraction on ‘Miniflex Rigaku ‘ X-ray diffractometer at Department of Physical Sciences, North Maharashtra University, Jalgaon, ( M. S. ) .

CuKi?? radiation ( i?¬ = 1.54051 Ao ) was used as a mark stuff. The sample rotated in the scope 5o to 80o ( 2i?± ) . The recorded X-ray diffractogram of undoped Sr oxalate crystals by hydro silicon oxide gel is as shown in fig. 3.4 and by agar-agar gel is as shown in fig. 3.5. From these diffractograms, strength ratio I/Io, ‘d ‘ spacing, matching Miller indices ( h K cubic decimeter ) were computed as shown in table- 3.1 and table-3.2.

These calculated ‘d ‘ values are matched with the reported 1s. ( h K cubic decimeter ) , ( a B degree Celsius ) and system calculated by the computing machine plan POWD ( Integrative Powder Diffraction and Indexing plan ) . These unit cell parametric quantities and system are shown in table- 3.1.1 and table- 3.2.1. These parametric quantities satisfy the conditions for anorthic system, i.e. the adult crystals have anorthic construction with a ? B ? degree Celsius and i?? ? i?? ?i?§ .

Table – 3.1 XRD informations of undoped Sr oxalate crystals by hydro-silica gel

Extremum

No.

2i?±

Deg.

FWHM

d- value

Intensity

I/Io

Indexs

H K cubic decimeter

1

28.050

0.118

3.1783

485

54

0 1 0

2

29.600

0.176

3.0153

128

15

1 1 0

3

37.750

0.059

2.3810

190

21

0 0 1

4

37.800

0.059

2.3779

265

30

-1 0 1

5

37.900

0.059

2.3719

207

23

0 -1 1

6

38.750

0.059

2.3218

108

12

-1 -1 1

8

38.950

0.059

2.3103

101

12

4 1 0

10

42.650

0.059

2.1181

183

21

-4 0 1

12

43.150

0.059

2.0947

115

13

5 1 0

17

45.250

0.059

2.0022

557

62

5 -1 1

19

49.050

0.059

1.8556

108

12

-5 -1 1

Table – 3.1.1 Unit cell parametric quantities and system of undoped Sr oxalate crystals by hydro-silica gel

Parameters

Strontium Oxalate

System

Triclinic

a

16.7505 Ao

B

3.4772 Ao

degree Celsiuss

2.5623 Ao

i??

111.393o

i??

90.441o

i?§

100.384o

Volt

136.41 Ao3

These parametric quantities satisfy the conditions for Triclinic System since a i‚? B i‚? degree Celsius and i?? i‚? i?? i‚? i?§ .

Table – 3.2 XRD informations of undoped Sr oxalate crystals by agar-agar gel

Extremum

No.

2i?±

Deg.

FWHM

d- value

Intensity

I/Io

Indexs

H K cubic decimeter

1

31.60

0.176

2.8289

107

24

0 1 0

2

36.35

0.294

2.4694

233

51

1 0 0

3

37.85

0.176

2.3749

352

77

0 1 1

4

41.10

0.176

2.1943

136

30

-1 1 0

5

41.70

0.294

2.1641

103

23

1 0 1

6

42.65

0.176

2.1181

112

25

-1 1 1

7

47.65

0.235

1.9068

460

100

-1 -1 2

8

49.50

0.176

1.8398

147

32

-1 -1 5

9

51.30

0.176

1.7794

135

30

1 -1 3

10

57.60

0.176

1.5989

121

27

0 -2 2

11

61.00

0.176

1.5176

102

23

0 -2 1

12

63.00

0.176

1.4742

132

29

1 1 1

13

69.40

0.235

1.3530

112

25

-2 0 3

14

76.20

0.176

1.2483

161

36

-1 -2 2

15

77.70

0.176

1.2279

105

23

2 -1 1

16

79.25

0.235

1.2078

117

26

-2 -1 4

Table – 3.2.1 Unit cell parametric quantities and system of undoped Sr oxalate crystals by agar-agar gel

Parameters

Strontium Oxalate

System

Triclinic

a

2.7219 Ao

B

3.2973 Ao

degree Celsiuss

11.0085 Ao

i??

116.524o

i??

108.889o

i?§

95.492o

Volt

80.20 Ao3

3.12.2 Fourier Transform Infrared Spectroscopy ( FT-IR )

About all-academic and industrial research labs make usage of infrared spectrometry as a bench tool for structural analysis. Although the IR spectra is the features of the full molecule, it turns out that certain groups of atoms give rise to sets at or near the same frequence regardless of the construction of the remainder of the molecule. Largely IR spectra are used in concurrence with other spectral informations to find molecular construction of the sample under survey.

In the present work IR spectra of Strontium Oxalate sample was recorded on JASCO instrument, Model 460 Plus at AISSMS College of Pharmacy, Pune, ( M. S. ) and University Department of Chemical Technology, North Maharashtra University, Jalgaon, ( M. S. ) on SHIMADZU FT-IR 8400 spectrophotometer.

The IR spectra of these gel grown Strontium Oxalate crystals were obtained in the moving ridge figure scope 400-4000 cm-1 for KBr line, accretion 70, declaration 4 cm-1, gain-auto ( 128 ) , scanning velocity -auto ( 2mm/sec. ) , apodization – cosine. The IR spectra obtained for the adult crystals in hydro silicon oxide gel is shown in fig. 3.6 and in agar- agar gel is shown in fig. 3.7.

IR surveies on assorted oxalates have been carried out by several research workers [ 6-8, 20, 21, 47-51, 90 ] .

IR spectra for undoped Sr oxalate crystals by hydro silicon oxide gel

In the IR spectrum of undoped Sr oxalate crystals, the soaking up at 3428.81 cm-1 is due to O-H stretching manner and H2O stretch. Few sets on the little wave figure side of these sets represent overtones and combination tones happening at smaller moving ridge figure.

A strong asymmetrical set at 1788.65 cm-1 is attributed to the C=O stretch of carbonyl group.

The peak 1351.86 cm-1 is due to of plane flexing O-H stretch, which established the presence of H2O molecule associated with crystal.

Around the peak 1071.26 cm-1 corresponds to the asymmetric stretching manner of C-O bond.

The crisp IR extremum at 719.318 cm-1 may be attributed to presence of metal-oxygen ( Sr-O manner ) bond.

The soaking up in between 610.36 to 562.148 cm-1 is due to presence of H2O of crystallisation.

Table – 3.3 Spectral assignments of the IR extremums

Wave figure ( cm-1 )

Assignment

3428.81

O-H Stretching

1788.65

C=O Stretching

1351.86

O-H bending

1071.26

C-O bond

719.318

metal – O bond

610.36 to 562.148

Water of crystallisation

IR spectra for undoped Sr oxalate crystals by agar- agar gel

In the IR spectrum of Sr oxalate crystals, the soaking up at 3301.54 cm-1 is due to O-H stretching manner and H2O stretch. Few sets on the little wave figure side of these sets represent overtones and combination tones happening at smaller moving ridge figure.

A strong asymmetrical set at 1608.34 cm-1 is attributed to the C=O

stretch of carbonyl group.

The peak 1316.18 cm-1 is due to of plane flexing O-H stretch, which

established the presence of H2O molecule associated with crystal.

The peak 1009.55 cm-1 is due to C-O stretching.

The crisp IR set observed at 859.132 cm-1 contains soaking ups caused

by C-C stretching.

The crisp IR extremum at 740.317 cm-1 may be attributed to presence of metal-

O ( Sr-O manner ) bond.

The soaking up from 668.214 cm-1 is due to presence of H2O of

crystallisation.

Table – 3.4 Spectral assignments of the IR extremums

Wave figure ( cm-1 )

Assignment

3301.54

O-H Stretching

1608.34

C=O Stretching

1316.18

O-H bending

1009.55

C-O bond

740.317

metal – O bond

668.214

Water of crystallisation

Therefore from above treatment the construction of undoped Sr oxalate may be

O = C – Oxygen

Sr xH2O ( x – unknown )

O = C – Oxygen

3.12.3 Thermal analysis

Thermal surveies of certain oxalates have been reported by several research workers [ 3-5, 7-9, 12, 20, 91 ] .

In the present work, TGA and DTA of undoped Sr oxalate was carried out 30oC to 600oC and 30oC to 1000oC at a heating rate of 10oC / min in an ambiance of air and the sample undoped Sr oxalate clasp for 1 minute at 30oC. DSC of undoped Sr oxalate was carried out 30oC to 400oC at a heating rate of 10oC / min and cooled from 400oC to 30oC at the rate of 10oC / min in N. The sample undoped Sr oxalate was hold for 1 minute at 30oC.

3.12.3.1 Thermo-Gravimetric Analysis ( TGA )

TGA was carried out on Diamond TG / DTA Perkin Elmer instrument at National Chemical Laboratory, Pune, ( M. S. ) and at University Department of Chemical Technology, North Maharashtra University, Jalgaon, ( M. S. ) on SHIMADZU DSC 600, Japan.

TGA curves are shown in fig. 3.8 for undoped Sr oxalate by hydro silicon oxide gel and in fig. 3.9 for undoped Sr oxalate by agar-agar gel.

From the thermo gm of undoped Sr oxalate by hydro silicon oxide gel one can detect that

The compound is stable up to 130.88oC.

8.887 % weight loss in temperature scope 130.88oC to 191.28oC may be due to desiccation of 0.85 H2O molecule and there is no farther weight loss up to 261.21oC.

18.253 % weight loss in temperature scope 261.21oC to 301.56oC from the dehydrated compound corresponds to loss of CO.

12.260 % weight loss in temperature scope 365.98oC to 498.55oC corresponds to loss of CO2.

The residue remains stable from 498.55oC.

TGA informations indicates that the adult crystals contains 0.85 H2O molecule, which is lost up to 261.21oC and dehydrated compound decomposed by fring CO up to 301.56oC. Again the compound decomposed by fring CO2 up to 498.55oC and after that the staying compound remains stable. These consequences can be interpreted by the following thermo chemical reactions.

130.88oC – 191.28oC

SrC2O4, 0.85 H2O SrC2O4 + 0.85H2O

Phase -I

261.21oC – 301.56oC

SrC2O4 SrCO3 + CO

Phase -II

365.98oC – 498.55oC

SrCO3 SrO + CO2

Phase -III

Percentage of weight loss in the different phases of decomposition of undoped Sr oxalate crystals are observed as reference in the table- 3.5.

Table — 3.5 Percentage of weight loss of undoped Sr oxalate crystals

by hydro-silica gel

Phase

Temperature

( oC )

Loss of stuff

Observed weight loss ( % )

Deliberate weight loss ( % )

I

130.88 to 191.28

0.85 H2O

8.887

7.929

Two

261.21 to 301.56

Carbon monoxide

18.253

18.784

Three

365.98 to 498.55

Carbon dioxide

12.260

11.816

Therefore the Sr carbonate eventually turns into Sr oxide at 498.55oC for undoped sample which is confirmed by residuary weight up to stop of analysis 60.600 % of SrO, which is in understanding with calculated residuary weight 61.471 % .

From the thermo gm of undoped Sr oxalate by agar-agar gel one can detect that

The compound is stable up to 121oC.

7.933 % weight loss in temperature scope 121oC to 240.47oC may be due to

desiccation of 0.85 H2O molecule and there is no farther weight loss up

to 251.19oC.

18.795 % weight loss in temperature scope 251.19oC to 356.87oC from the

dehydrated compound corresponds to loss of CO.

11.83 % weight loss in temperature scope 359.94oC to 497.74oC corresponds to loss of CO2.

The residue remains stable from 497.74oC.

TGA informations indicates that the adult crystals contains 0.85 H2O molecule, which is lost up to 240.47oC and dehydrated compound decomposed by fring CO up to 356.87oC. Again the compound decomposed by fring CO2 up to 497.74oC and after that the staying compound remains stable. These consequences can be interpreted by the following thermo chemical reactions.

121oC-240.47oC

SrC2O4, 0.85 H2O SrC2O4 + 0.85H2O

Phase -I

251.19oC-356.87oC

SrC2O4 SrCO3 + CO

Phase -II

359.94oC-497.74oC

SrCO3 SrO + CO2

Phase -III

Percentage of weight loss in the different phases of decomposition of undoped Sr oxalate crystals are observed as reference in the table- 3.6.

Table — 3.6 Percentage of weight loss of undoped Sr oxalate crystals

by agar-agar gel

Phase

Temperature

( oC )

Loss of stuff

Observed weight loss ( % )

Deliberate weight loss ( % )

I

121.00 to 240.47

0.85 H2O

7.933

7.929

Two

251.19 to 356.87

Carbon monoxide

18.795

18.784

Three

359.94 to 497.74

Carbon dioxide

11.830

11.816

Therefore the Sr carbonate eventually turns into Sr oxide at 497.74oC for undoped sample which is confirmed by residuary weight up to stop of analysis 61.442 % of SrO, which is in understanding with calculated residuary weight 61.471 % as shown in table- 3.6.

3.12.3.2 Differential Thermal Analysis ( DTA )

DTA was carried out on Diamond TG / DTA Perkin Elmer instrument at National Chemical Laboratory, Pune, ( M. S. ) .

DTA curves are shown in fig. 3.10 for undoped Sr oxalate by hydro silicon oxide gel and in fig. 3.11 for undoped Sr oxalate by agar-agar gel.

From DTA curve of undoped Sr oxalate by hydro silicon oxide gel one can detect that the loss of majority of H2O of crystallisation in a individual ailing endothermic at 185.99oC. Complete desiccation is merely on the oncoming of oxalate decomposition as ascertained. DTA curve at the extremum 293.34oC and 505.02oC are characterized by an exothermal extremum which shows the oxalate decomposition.

Loss of weight at the temperature relates to the loss of H2O of crystallisation ( endothermal reaction ) at the scope 101.04oC to 211.49oC.

Loss of weight at the temperature 293.34oC relates to let go of of CO and loss of weight at the temperature 505.02oC relates to let go of of CO2 which are exothermal in character. That means the weight loss with regard to temperature of the adult crystals was farther supported by DTA consequences. DTA information is shown in table- 3.7.

Table — 3.7 DTA informations of undoped Sr oxalate crystals by hydro silicon oxide gel

On set

( oC )

Extremums Recorded

( oC )

Peak Height

( i?­v )

Area

( i?­v.s )

Nature

166.37

185.99

-23.029

5058.205

Endothermic

276.15

293.34

10.773

-22847.144

Exothermic

499.74

505.53

20.350

-7846.491

Exothermic

From DTA curve of undoped Sr oxalate by agar-agar gel one can detect that the loss of majority of H2O of crystallisation in a individual ailing endothermic at 172.47oC. Complete desiccation is merely on the oncoming of oxalate decomposition as ascertained. DTA curve at the extremum 315.91oC and 481.36oC are characterized by an exothermal extremum which shows the oxalate decomposition.

Loss of weight at the temperature relates to the loss of H2O of crystallisation ( endothermal reaction ) at the scope 111.04oC to 243.49oC.

Loss of weight at the temperature 315.91oC relates to let go of of CO and loss of weight at the temperature 481.36oC relates to let go of of CO2 which are exothermal in character. That means the weight loss with regard to temperature of the adult crystals was farther supported by DTA consequences. DTA information is shown in table- 3.8.

Table — 3.8 DTA informations of undoped Sr oxalate crystals by agar-agar gel

On set

( oC )

Extremums Recorded

( oC )

Peak Height

( i?­v )

Area

( i?­v.s )

Nature

163.25

172.47

-99.791

19241.244

Endothermic

309.02

315.91

37.272

-1023.200

Exothermic

426.63

481.36

519.138

-34084.412

Exothermic

3.12.3.3 Differential Scanning Calorimetry ( DSC )

DSC was carried out on Perkin Elmer instrument Pyris 6 DSC at National Chemical Laboratory, Pune, ( M. S. ) and at University Department of Chemical Technology, North Maharashtra University, Jalgaon, ( M. S. ) on SHIMADZU DSC 600, Japan.

DSC curves are shown in fig. 3.12 for undoped Sr oxalate by hydro silicon oxide gel and in fig. 3.13 for undoped Sr oxalate by agar-agar gel.

From DSC curve of undoped Sr oxalate by hydro silicon oxide gel one can

observe that:

Step-I

The induction temperature is 132.50oC and equilibrium temperature is 220oC. At 132.50oC induction of stage alteration start and stage alteration is completed at peak endo-down temperature 169.45oC. The temperature at which the sample and mention semen to the thermic equilibrium by thermic diffusion appears to be at 220oC.

Area under the curve is 4460.46 mJ.

Heat of passage ?H i.e. enthalpy alteration of passage is 220.0645 J/gm ; this is 0.2201 KJ/mole. Since molecular weight is 1 gm/mole.

Therefore, ?Htr = ?Hf

Hence heat of stage formation is besides 0.2201 KJ/mole.

Where ?Hf is enthalpy alteration of new stage formation or it is called heat of stage formation.

Step-II

At 230.10oC induction of stage alteration start and stage alteration is completed at peak endo-down temperature 299.10oC.

In the DSC study the two endothermal phases were obtained at 169.45oC and 299.10oC severally. The consequence of DSC measuring is presented in the table- 3.9.

Table — 3.9 DSC measurings of undoped Sr oxalate crystals by hydro-silica gel

Sample

Wt of the sample

Change in heat content ?Hf

Passage temperature

Undoped Strontium Oxalate

7.900 milligram

0.2201 KJ/mole

169.45oC

From DSC curve of undoped Sr oxalate by agar-agar gel one can detect that:

Step-I

The induction temperature is 131.46oC and equilibrium temperature is 219.36oC. At 131.46oC induction of stage alteration start and stage alteration is completed at peak endo-down temperature 171.56oC. The temperature at which the sample and mention semen to the thermic equilibrium by thermic diffusion appears to be at 219.36oC.

Area under the curve is 4452.803 mJ.

Heat of passage ?H i.e. enthalpy alteration of passage is 214.0771 J/gm ; this is 0.2141 KJ/mole. Since molecular weight is 1 gm/mole.

Therefore, ?Htr = ?Hf

Hence heat of stage formation is besides 0.2141 KJ/mole.

Where ?Hf is enthalpy alteration of new stage formation or it is called heat of stage formation.

Step-II

The induction temperature is 229.07oC and equilibrium temperature is 352.53oC. At 229.07oC induction of stage alteration start and stage alteration is completed at peak endo-down temperature 304.26oC. The temperature at which the sample and mention semen to the thermic equilibrium by thermic diffusion appears to be at 352.53oC.

Area under the curve is 3964.438 mJ.

Heat of passage ?H i.e. enthalpy alteration of passage is 190.5980 J/gm ; this is 0.1906 KJ/mole. Since molecular weight is 1 gm/mole.

Therefore, ?Htr = ?Hf

Hence heat of stage formation is besides 0.1906 KJ/mole.

Where ?Hf is enthalpy alteration of new stage formation or it is called heat of stage formation.

In the DSC study the two endothermal phases were obtained at 171.56oC and 304.26oC severally. The consequence of DSC measuring is presented in the table- 3.10.

Table — 3.10 DSC measurings of undoped Sr oxalate crystals by

agar- agar gel

Sample

Wt of the sample

Change in heat content ?Hf

Passage temperature

Undoped Strontium Oxalate

20.800 milligram

0.2141 KJ/mole

171.56oC

0.1906 KJ/mole

304.26oC

Chemical analysis

Chemical analysis was carried out at Department of chemical science, Shri Shivaji Vidya Prasarak Santha ‘s Bapusaheb Shivajirao Deore College of Engineering, Dhule, ( M. S. ) .

1. Gravimetric method

Strontium is quantitatively estimated as Sr sulfate, from the adult crystals of undoped Sr oxalate. 1 gram of crystals were dissolved in hydrochloric acid and diluted to 100 milliliter with distilled H2O. In a boiling solution slight surplus of hot 0.5 M sulfuric acid solution was added easy with changeless stirring and precipitate was filtered in a leaden porcelain- filter melting pot, washed with hot acidified H2O and so with warm distilled H2O. It was dried in electric muffle furnace at 600oC and allowed to chill and take the weight.

The estimated sum of Sr was found 65.45 % in the adult crystals by hydrometric analysis is in understanding with the deliberate sum of Sr, ( 64.40 % ) in SrC2O4, 0.85H2O.

2. Volumetric Analysis

Strontium is quantitatively estimated volumetrically utilizing standard EDTA solutions. 0.0135 gram of Sr oxalate crystals were dissolved in 100 ml de-ionized H2O with few beads of HCL ( 0.01N solution ) . 25 milliliter of this solution was pipette in a titration flask, 12.1 pH was adjusted by the add-on of 1M Na hydrated oxide solution in it and Eriochrome black T was added as an index. It was titrated with 0.01 N ( criterion ) EDTA solutions until the coloring materials changed from bluish to grey.

1mole EDTA = 1 mole Sr2+

i.e. 1000 milliliter 1 mole EDTA contain 87.63 gram Sr

As 25 milliliter pipette solution required 24.7 milliliter 0.01N, EDTA

i??100 ml solution required = 98.8, 0.01 N EDTA

As 1000 milliliter 0.01N EDTA = 0.08763 gram Sr2+

i??98.8, 0.01N EDTA = 0.008657 gram Sr2+

As 0.0135 gram of Sr oxalate solution = 0.008657 gram Sr

i??100 gram of Sr oxalate solution contains = 64.13 gram Sr

Therefore the volumetric appraisal of Sr in the adult crystals was found to be 64.13 % . This is matched with the deliberate sum ( 64.40 % ) of Sr in SrC2O4, 0.85 H2O.

Energy Dispersive Analysis by X-rays ( EDAX )

Elemental analysis was carried out at Sophisticated Instrumentation Centre for

Applied Research and Testing ( SICART ) , Sardar Patel Centre for Science and Technology, Aanand, Gujarat.

The graph of the sample undoped strontium oxalate grown in hydro-silica gel

obtained after EDAX is shown in fig. 3.14 and the information obtained is given in table- 3.11, which shows mass ( wt ) % of different elements in the sample. The presence of Sr metal is confirmed from EDAX. The ascertained mass ( wt ) % is in understanding with deliberate one.

Table — 3.11 EDAX informations of undoped Sr oxalate crystals by hydro-silica gel

Component

Content as measured by EDAX

wt %

at %

C

7.83

23.85

Oxygen

20.13

46.05

Strontium

72.05

30.10

The graph of the sample undoped strontium oxalate grown in agar-agar gel obtained after EDAX is shown in fig. 3.15 and the information obtained is given in table- 3.12, which shows mass ( wt ) % of different elements in the sample. The presence of Sr metal is confirmed from EDAX. The ascertained mass ( wt ) % is in understanding with deliberate one.

Table — 3.12 EDAX informations of undoped Sr oxalate crystals by agar-agar gel

Component

Content as measured by EDAX

wt %

at %

C

12.28

32.57

Oxygen

21.84

43.48

Strontium

65.88

23.95

3.12.6 Scaning Electron Microscope ( SEM )

In present work Scanning Electron Microscope ( SEM ) surveies of gel grown undoped strontium oxalate crystals by hydro silicon oxide gel and agar-agar gel are done by utilizing latest computerized scanning negatron microscope Quanta 200 3D at National Chemical Laboratory, Pune, ( M. S. ) . The consecutive exposure were taken at magnification of 250- , 500- and 2500- at width 15.1 millimeter, 14.9 millimeter severally and at high electromotive force 20 KV for undoped Sr oxalate crystals by hydro silicon oxide gel as shown in fig.3.16 ( a, B, degree Celsius ) . While the consecutive exposure were taken at magnification of 250- , 500- , 1000- and 2000- , at common breadth 14.7 millimeter and at high electromotive force 20 KV for undoped Sr oxalate crystals by agar-agar gel as shown in fig. 3.17 ( vitamin D, vitamin E, degree Fahrenheit, g ) .

Fig. ( a ) shows the surface of undoped Sr oxalate crystals grown in hydro silicon oxide gel. The whole surface is dark but in within the surface one can see white regular geometrical images of different form and size. In general within the surface there are white images on the dark background. The geometrical forms of the white images are largely pentagon but they are irregularly oriented. If the part A of fig. ( a ) at magnification 250- is observed at higher magnification it is shown by part A1 in fig. ( B ) . All the four figures on the part A are good isolated in part A1. One of the figure in A1 is regular hexagonal while the 2nd is irregular Pentagon, the 3rd is regular square and 4th is without any form. But all the four figures in part A1 have little grains on the surface.

If the part B on A1 in fig. ( B ) that is square and is farther magnified its geometrical nature and grains on the surface is clearly seen in part B1 in fig. ( degree Celsius ) at higher magnification 2500- .

If the surface of undoped Sr oxalate crystals grown in agar-agar gel observed at magnification 250- it can be represented by fig. ( vitamin D ) and it shows in general Pentagon. The growing beds organizing the construction of Pentagon are clearly seeable. The growing beds of different faces are parallel to each other. As the growing beds organizing the hexangular knoll are clearly seen. It can be stated that the growing of the knoll in peculiar and growing of the crystal in general takes topographic point by two dimensional mechanisms. Portion A of fig. ( vitamin D ) is magnified and shown by part A1 in fig. ( vitamin E ) at magnification 500- . The part A1 shows the well defined borders of the geometrical figures.

The part B in fig. ( vitamin E ) which is a portion of A1 is farther magnified, it is shown by the part B1 in fig. ( f ) at magnification 1000- . The part B1 shows clearly formation of growing knolls by growing beds that is growing by two dimensional mechanisms.

The geometrical nature of the part C, which is a portion of B1 of fig. ( degree Fahrenheit ) is shown by the part C1 which is extremely magnified as shown in fig. ( g ) at magnification 2000- . Because of higher magnification of fig ( g ) the strength of the figure in general is reduced, but the borders of the geometrical figure are rather crisp and clearly seeable.

Decisions

From the above treatment, the undermentioned decisions can be derived:

Gel technique can be successfully employed for growing of undoped Sr oxalate crystals. Single diffusion method is convenient for growing of the crystals. Micro crystals of Sr oxalate were observed in hydro-silica gel at 4.0 pH value with gel denseness ( 1.04gm/cc ) , white transparent, bantam, reflecting crystals were obtained in agar gel, i.e. size of the crystals improved in agar- agar gel.

Gel aging period reduces the nucleation centres without impacting the quality of crystals.

Nucleation denseness was increased with the concentration of reactants. Concentration of reactants has pronounced consequence on the wont, quality and size of the crystals. Rate of diffusion of supernatant has great consequence on the quality of crystals.

From the survey of XRD, IR, TGA, DTA, DSC, EDAX and SEM of undoped sample of strontium oxalate following decisions can be predicated:

From XRD the unit cell parametric quantities of grown undoped Sr oxalate crystals satisfy the conditions for anorthic system.

From FT-IR foremost four sets are on lower moving ridge figure, metal-oxygen bond and H2O of crystallisation on higher moving ridge figure in agar-agar gel.

For the decomposition of adult crystals the temperature scope in hydro-silica gel is somewhat more every bit compared to agar-agar gel hence the thermic stableness of adult crystals is same.

Chemical composings of the adult crystals by EDAX are about same with the theoretical computation. The per centum of Sr in the crystals grown by hydro-silica gel is more every bit compared to that is grown by agar-agar gel.