4905 - 6 .] Study of Liquid Sulgghur as Dynamic Isomers. 353 
during the heating, to accelerate the adjustment, and then using 
sulphur dioxide before chilling, in order to retard the reverse 
change. 
All the gases named above act as simple catalytic agents. 
Iodine retards the adjustment to equilibrium also, hut it likewise 
acts as, a second component in the system and displaces markedly 
the equilibrium. Two parts of iodine to one hundred of sulphur 
at 150° increase the by 7 per cent., and at 448° by 30 per cent. 
The two liquid forms of sulphur, S A and S^, are to he classed as 
“dynamic isomers.” The freezing-point of the former is 119*25° 
(these Proceedings , voL xxiv. (1902), p. 300); that of the latter is 
unknown. In presence of ammonia the freezing-point is 114*5°. 
This is the temperature at which the two liquid forms of sulphur 
are in equilibrium with one another and also with solid, monoclinic 
sulphur. It is the triple point or so-called “natural freezing- 
point.” At this point the proportions of S A and in the liquid 
are 96*3 and 3*7 per cent, respectively. It has not been possible 
to observe any freezing-point and simultaneously measure the 
proportion of (by chilling ; these Proceedings , vol. xxiv. 
(1902), p. 299), below 112*45°, where the proportion of was 
5*3 per cent. In the figure, which is drawn to scale, these facts are 
shown diagrammatically. A is the freezing-point of S A (119*25°, 
— 0), D the natural freezing-point (114*5°, S jU =3*7 per cent.), 
PROC. ROY. SOC. EDIN., YOL. XXYI. 23 
