Thermal analysis of elemental sulphur
Allotrope Transition
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currell1974| Allotrope
|
Transition | ||
|
Temperature (’C) | |||
|
s« |
s,- |
*Si |
112 |
|
s. |
s,- |
*Si |
119 |
|
So |
So—> sOI |
115 | |
|
S« |
Si- |
|
100 |
|
Si |
Si- |
|
170 |
Sx liquid S8 5ш1 liquid polymer
Se mixture monomer and polymer
give the weight of S2 present in the sample. This area is proportional to both the weight of S_ and energy of transition (A/7f = 12.54 J g-1). Similarly, the S^ fusion peak is proportional to the weight, Sa+S^, present in the original sample and the energy of transition (A//f = 53.42 J g-Note that any Sa present in the original sample is converted to before fusion.
It is not possible to determine the allotropic nature of flowers of sulphur or sulphur which has been rapidly cooled from the melt above 159 °C. These samples contain bcth monomer and polymer and because of the broad poorly resolved endotherm obtained for monomeric sulphur in the presence of polymer, it is not possible to integrate the area for each fraction, i.e., monomer or polymer.
Ten determinations of crystalline sulphur (Sa+Sp) were carried out on a mixture of sulphur and polymeric polysulphides. An average value of 64.3% with a standard deviation of 2.15 was obtained.
EXPERIMENTAL
A Perkin-Elmer DSC-1B calorimeter was used for all measurements. For the indium standard a scan rate of 4°C min-1, sensitivity 8 meal, and chart speed of 20 mm min-1 were used. For the sulphur samples, a scan rate 4CC min- *, sensitivity 4 meal, and chart speed 20 mm min -1 were employed. Sample sizes were 15-20 mg. Static air atmosphere.
ACKNOWLEDGEMENT
The authors gratefully acknowledge financial assistance from The Sulphur Institute.
REFERENCES
G. W. Miller, J. Appl. Polym. Sci., 15 (1971) 1985.
M. Barnes, in B. Meyer (ed.), Elemental Sulphur, Interscience, New York, 1965, p. 86.
E. D. West, J. Amer. Chem. Sac., 81 (1959) 29.
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