590 Proceedings of Royal Society of Edinburgh. [sess. 
The Nature of Amorphous Sulphur, and Contributions 
to the Study of the Influence of Foreign Bodies on 
the Phenomena of Supercooling observed when 
Melted Sulphur is suddenly Chilled. By Alexander 
Smith. 
(MS. received February 17, 1905. Read March 20, 1905.) 
{Abstract.) 
1. The hardening of plastic sulphur was investigated, and it was 
found that partial reversion to soluble sulphur prevents the securing 
in quasi-solid form of the whole of the amorphous sulphur present. 
It was discovered, however, that sulphur formed by precipitation 
in presence of concentrated acids does yield 100 per cent, of 
insoluble sulphur, and that only the impossibility of realising the 
requisite condition of very fine subdivision is therefore responsible 
for the smaller yields from melted sulphur which has reached the 
highest temperatures previous to being chilled. 
2. A new series of measurements of the proportions of insoluble 
sulphur formed when common sulphur is chilled from various 
temperatures was made. The amounts vary from 4*2 per cent, at 
130° to 34 per cent, at 448°. In this, and in all other cases 
described below, only the insoluble sulphur which remains after 
the viscous material has completely hardened was estimated. 
3. It was found that when sulphur was subjected to prolonged 
heating at 448°, or was heated for a shorter time in vacuo, or was 
used immediately after recrystallisation, or was washed with water 
before being heated, the amount of insoluble sulphur obtainable 
by chilling was greatly reduced. The effects of these modes 
of treatment seemed to be to remove a trace of sulphuric acid 
which sulphur acquires by exposure to the air. 
4. It appeared that gases like carbon dioxide, and particularly 
ammonia and hydrogen sulphide, when led through melted sulphur, 
