1906-7.] 
Precipitated Sulphur. 
311 
Concern of 
HC1 used 
After 
mixing 
Concen. Na 2 S 2 0 3 
and Per cent. Am S. 
State of Sulphur from 
2 N. Na 2 S 2 0 3 . 
2 N 
4N 
6 N 
2 N 
N 
6-1 
Yellow-brown viscous oil. 
3N 
1JN 
12-4 
14-7 
8-3 
5N 
2^N 
21*5 
18-9 
29-0 
More viscous oil. 
ION 
5 N 
47-0 
45-9 
57-7 
V ery viscous oil. 
12 N 
6 N 
68-8 
72-3 
75-9 
Non- viscous powder. 
A study of the foregoing, and of the other series not here given, 
showed — 
(1) That the proportion of insoluble sulphur is not dependent upon an 
excess of acid, for much amorphous sulphur was formed when the salt 
was in excess. 
(2) That the proportion of insoluble sulphur is proportional to the con- 
centration of the acid immediately after mixing. 
(3) That the proportions were smaller the higher the temperature of 
precipitation. 
The question which finally presented itself was whether the excess 
of acid, which is so potent in increasing the yield of amorphous sulphur, 
operates in this way during the liberation of the sulphur, or exercises this 
influence by contact with the sulphur after liberation. Actual experiment 
showed that subsequent mixing of the liberated sulphur with more 
concentrated acid was as effective as using the larger excess during the 
precipitation. 
The mechanism of the action is therefore as follows : — The sulphur 
from the thiosulphate, when first liberated, is wholly S M . With little 
acid present this changes largely to S A , and the S A finally solidifies to 
soluble sulphur. A more concentrated acid retards the change to S A , and 
permits the hardening and preservation of a larger proportion of the S M . 
Acid substances such as retard the transformation S M ->S A in melted 
sulphur operate, therefore, in the same way with suspended liquid sulphur. 
It is the fact that the sulphur is first liberated as that alone renders 
the production of amorphous sulphur possible. This liberation first in 
the least stable form is in accordance with the law of transformation 
by steps (Ostwald), which successfully explains the behaviour of so many 
substances. 
University op Chicago, 
April 1907. 
(Issued separately October 3, 1907.) 
