THE CRYSTALLISATION OF ALKALINE-EARTH METAL TUNGSTATES FROM SOLUTIONS IN SODIUM TUNGSTATE MELTS A Thesis for the Degree of Master of Science in the School of Natural Sciences of the Universiti Sains Malaysia, Penang by Appalasami Subramaniam School of Chemical Science, Universiti Sains Malaysia, Penang, Malaysia March 1977
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THE CRYSTALLISATION OF ALKALINE-EARTH METAL TUNGSTATES
FROM SOLUTIONS IN SODIUM TUNGSTATE MELTS
A Thesis for the Degree of Master of Science
in the
School of Natural Sciences
of the
Universiti Sains Malaysia, Penang
by
Appalasami Subramaniam
School of Chemical Science,
Universiti Sains Malaysia,
Penang, Malaysia March 1977
ACKNOWLEDGEMENTS
This work was carried out at the Physical Chemistry Section, School
of Chemical Sciences, Universiti Sains Malaysia, Penang, over the past two
years.
The author wishes to express his indebtedness, deep gratitude and thanks
to Dr. Bimalendu Narayan Roy 1 Lecturer, School of Chemical Sciences, for
his constant ungru,dging guidance and day-to-day supervision of this original
piece of work. The author would like to thank the authorities of the School
of Chemical Sciences for providing the necessary facilities for this work.
The author also wishes to express his thanks to:
Professor N .K. Nair, School of Chemical Sciences, Universiti Sains
Malaysia, for his valuable suggestions and kind encouragement.
Professor Chatar Singh, Dean of School of Physics, for providing X-ray
faei lities and access to other instruments and to Dr. Mehrothra for his
valuable suggestions in X -ray work •
Mr. Oon Liang Gan, Mr. Teh Choo Aun, Mr. Tan Chin Tong,
Mr. Amanullah and Mr. Hussain for their help in day-to-day
experimental work •
Mr 9 Tan Eng Cheong .and Mr. Ahmad, School of Physics, for their
help in developing and printing films.
The author acknowledges with thanks the financial support in the form
of a tutorship from Universiti Sains Malaysia during the period of this work.
The author wishes to express his deep gratitude and thanks to his dear
friend, Mr. Jeffry Choong, who ungrudgingly sacrificed his time and energy
to type this whole thesis.
last, but not least, the author wishes to express his thanks to
Miss P .C. Sushama, for her kind permission to use her IBM Executive
Crystallisation -- with Differentia! Thermal Analysis • • • 48
RESULTS 51
Section 1
Solubilities of Alkaline-earth Metal Salts in Sodiun Tungstate at Various Temperatures • • • • • • • • • • • • • 51
Section 11
Preliminary General Studies on Crystallisation of Alkaline-earth Metal Salts from Metal Chloride Melts-Nucleation and Final Crystal Sizes ••• ~. ~............ 56
Section 111
Crystallisation of Alkaline-earth Metal Tungstates from Sodiun Tungstate Melts by Continuous Cooling 58
I ntr od uc tion ···~··~·~································· 58
A. Crystallisation in Aluninct Crucible$ • ••••••••••••••••• 59
1/1. Solubilities of Alkaline-earth Metal Tungstates in Sodi urn Tungstate. Approximate .6.Hf - values ( kcal/mole ) • • • • • • • • • • • • • • • 55
111/1. Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( Alumina crucibles ) Final Average Crystal lengths, Shape Factors and Nucleus Numbers, ••••••.•••• •.................. •• • • • • 84
111/2. Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( Alumina crucibles) Initial Growth Rates .............................. , •·• •••• •••. • •.••. , 88
111/3. Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( Alumina crucibles) Diffusion Rate Constants ...................... •·•·•·•·•·•·•·•·•-•·•·•• • 95
111/4. Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( PI ati num crucibles ) Induction Periods .............................. -•- ... , , • • • • 121
111/5. Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( Platinum crucibles ) I ni ti al Growth Rates ................ • •••••••.••.•••••• -• • • 124
111/5A. Crystallisation of Alkaline-earth Metal Tungstotes at different temperatures ( Platinum crucibles ) Initial Growth Rates ( at t = t) • •••••• •• • •• • • • • • • • • • • • 125
111/6. Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( Platinum crucibles ) Diffusion Rate Constants •••••••••••••••••••••••••••••• 133
111/6A.,
J.
2.
3.
APPENDIX
Table
1 •
Crystallisation of Alkaline-earth Metal Tungstates at different temperatures ( Platinum. crucibles)
Crystallisation of Calcium tungstate in Sodium tungstate melt by continuous cooling ( Platinum crucible ) Experimental data for degree of crystallisation (oct) at any crystallisation time( t ) ••••••••••••• , • • • • • • • • • • • 187
Crystallisation of Strontium tungstate in Sodium tungstate melt by continuous cooling ( Platinum crucible ) Experimental data for degree of crystallisation (ext) at any crystallisation time ( tl)... •• • • • • • • • •• • • • •• • • • • • • 19'1
Crystallisation of Barium tungstate in Sodium tungstate melt by continous cooling ( Platinum crucible ) · Experimental data for degree of crystallisation (oct ) at any crystallisation time ( t ) ••••••• , ••• , •••• , • • • • • •• )99
VI
LIST OF FIGURES
Figure Page
1/1. Soluhility of Alkalir.e-earth Metal Tungstates in Sodium Tung:;~·cte Melts at different temperatures...... 53
1/2. Solubility of Alkaline-earth Metal Tungstates in Sodium Tungstate Melts at different temperatures
Crystallisation of Alkaline-earth Metal Tungstates from Solutions in Sodium Tungstate Melts ( Alumina crucible) • T = aod'C; Rf = 120~~Yhr. Extents of crystallisation° after different times •••••• _.. 76
Cl'ystallisation of Alkaline-earth Metal Tungstates from Solutions in Sodium Tungstate Melts (Alumina crucible) • T = 9000C; Rr = 120°C/hr •••. Extents of crystallisation°after different times •••••• ~.. 77
Crystal I isation of AI kal i ne-earth Metal T ungstates from Solutions in Sodium Tungstate Melts (Alumino crucible) •. T = 1000°C; ')- = 120°C/hr •. Extents of crystollisation° after different times......... 78
Crystallisation of CalciiJm Tungstate from Sglotioos in Sodium Tung"!tcte 1/.e!tz ( ALup.tino crucihle ). T
0 = 1000°C.
Maximum crystal lengths after different times......... 79
Crystallisation of Strontium Tungstate from Solutions ·in Sodium Tungstate Melts (Alumina crucible ). T = 1000°C. Maximum crystal len9t!1s after different times •• ~...... BO
Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts (Alumina crucible). T = 1000°C. Maximum crystal lengths after different times •• ~...... 81
111/7.
111/8.
111/9.
111/10.
111/11.
111/12.
111/13.
IJ 1/14.
111/15~
111/16.
vii
Crystallisation of Calcium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible ) T = 300°C. Extents of crystallisation after different times.? •••••••••••••• 100
Crystallisation of Calcium Tungstate from Solutions in0
Sodium Tungstate Melts ( Platinum crucible) T = 900 C. Extents of crystal I isation after different times.? •••••••••••
Crystallisation of Calcium Tungstate from Solutions in Sodium Tungstate Melts ( PlatinLtm crucible) T = IOOO.oC. Extents of crystallisation after different times.? •••••••••••
Crystallisation of Strontium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible } T = 800°C. Extents of crystal! isation after different times.? •••••••••••
Crystallisation of Strontium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible ) T
0 = 900°C.
Extents of crystallisation after different times •••••••••••••
Crystallisation of Strontium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) To= 1000°C. Extents of crystallisation after different times •••••••••••••
Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) T
0 = qQ0°C.
Extents of crystallisation after different times •••••••••••••
Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible ) T = 90C:PC. Extents of crystallisation after different times.? •••••••••••
Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible ) T
0 = 1000°C.
Extents of crystallisation after different times •••••••••••••
Crystallisation of Calcium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) T = 800°C. Maximum crystal lengths after lfifferent times.? ••••••••••••
101
102
103
104 i'
105
106
107
108
111
vfii
111/17. Crystallisation of Calcium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) T0 = 900°C. Maximum crystal lengths after different times ••••••••••• 112
111/18. Crystallisation of Calcium Tungstate from Solutions in Sodium Tungstate Melts. ( Platinum crucible) T = 1000°C. Maximum crystal lengths after diff.arent times •• ~ •••••••• 113
111/19. Crystallisation of Strontium Tungstate from Solutions in Sodium Tungstate Melts { Platinum crucible) T0 = 800°C • Maximum crystal lengths after different times ••••••••••• 114
111/20. Crystallisation of Strontium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) T
0 = 900°C.
Maximum crystal lengths after different times ............ 115
111/21. CrystoUisation of Strontium Tungstate from Solutions in Sodium Tungstate Melts { Platinum crucible ) T0 = 1000°C. l\1\aximum crystal lengths after different times,,~ •••••••• 116
111/22. Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible ) T = 800°C. Maximum crystal lengths after different times.? ••••••••• 117
111/23. Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) T = 900°C. Maximum crystal lengths after different times.~ ••••••••• 118
111/24. Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Platinum crucible) T = 1000°C. Maxim urn crystal I eng ths after different times.~ ••••••••• 119
111/25 Crystallisation of Strontium Tungstate f-rdm Solutions in Sodium Tungstate Melts { Pla2num crucible) T
0 = 1000°C.
127 ( Maximum crystal lengths ) after different times •••••••
111/26. Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts ( Pla~inum crucible) T0 = 90d'C.
128 { Maximum crystal lengths ) after different times •••••••
111/27.
._ ix
Crystallisation of Barium Tungstate from Solutions in Sodium Tungstate Melts { Pla:2inum crucible) T = l000°C. (Maximum crystal lengths) after different ti~es...... 129
a = A = c = C· = I
ce = Co = 'sat = tt = c = D =
} = =
lav =
tfav)fin
lr.n =
.t.t = ko =
:( ko =
w N = Rc = Rs =
~ = =
5 = t = t = T = T· = I
Tf = To =
LIST OF SYMBOLS
( = dC/dT ) change of solute concentration with respect to temperature
area solute concentration initial solute concentration eutectic concentration solute concentration at initial starting temperature saturation solvte ooncentration iolute concentration at any time solute concentration at induction period diffusion coefficient shape foc;tor crystal length average CryJtal length
final average crystal I ength
final maximum crystal length
moximt.m crystal length at any time Cllffuelon rate constant for etystal length
diffusion rate constant for crystal width
nucleus number rate of mixing ( = dS/dt} rate of development of supersaturation ( = dT / dt ) rate of cooling supersaturation
alpersaturation at induction period time induction period temperatwe initial temperah.re .final temperature initial starting temperature
xi
Tx = crystallisation temperature
-T = induction temperature w = crystal width wav = average crystal width
{ waJfin = final average crystal width
wt = maximum crystal width at any time
wfin = fi nat maximum crystal width
w = crystal weight
ex. = ext~nt of crystallisation 6 = crystal thickness
'1 = crystal density = viscosity
" = porosity c: = growth time after induction period
Psoln = density of sol uti on
ABSTRAK
Kerja ini mengemukakan suatu kajian mengenai penghabluran
Tungstat logam A~kali -Bumi dari larutan lebur Natrium Tungstat.