352 Proceedings of Royal Society of Edinburgh. [skss. 
Further Study of the two Forms of Liquid Sulphur 
as Dynamic Isomers. By Alexander Smith and 
C. M. Carson. 
(MS. received July 13, 1906. Read July 13, 1906.) 
(Abstract.) 
When sulphur to which after recrystallisation no air has had 
access is melted, or when ammonia is led for a few minutes through 
ordinary sulphur after it has been melted, the two forms of liquid 
sulphur (yellow, mobile S A , and brown, viscous S^) adjust them- 
selves very rapidly to those proportions which are in equilibrium 
at that temperature to which the liquid may have been raised. 
The adjustment occupies but a few moments. When specimens 
thus prepared are then chilled by plunging into water, the reversion 
of the to S\ is equally rapid, and therefore the product is wholly 
brittle, crystalline, monoclinic sulphur. This behaviour is observed 
whether the liquid has been heated at, say, 155°, where the 
amount of at equilibrium is 7*2 per cent., or at 448°, where the 
amount is at least 34 per cent. 
Sulphur which has been exposed to the air since recrystallisation, 
when melted, reaches a condition of equilibrium with measurable 
slowness at the lower temperatures. Thus at 155° the proportion 
of Sjt at the end of an hour is only 6 '8 percent., and not until 
nearly two hours have elapsed does it reach 7*2 per cent. Leading 
a few bubbles of sulphur dioxide or of hydrogen chloride through 
melted sulphur which since recrystallisation has never been exposed 
to the air confers upon it the same slowness in reaching equilibrium. 
Specimens of ordinary sulphur, and of sulphur treated with sulphur 
dioxide, therefore, when chilled do not lose their content of 
S M by reversion. Hence practically the whole amount present at 
equilibrium at a given temperature may be supercooled and obtained 
after extraction of the mass eventually as amorphous sulphur. 
Thus the proportions at equilibrium at any temperature may 
most quickly and accurately be measured by leading in ammonia 
