248 Proceedings of Royal Society of Edinburgh. [sess.. 
Note on Crystalline Hydrates of Sodium Thiosulphate, 
By W. W. Taylor, M.A., B.Sc. Communicated by Pro- 
fessor Crum Brown. 
(Read June 20, 1398.) 
During the winter session I had occasion to prepare several 
supersaturated solutions for lecture demonstration. Among them 
was a solution made by fusing crystals of sodium thiosulphate. 
Next day this solution had deposited a considerable quantity of 
crystals, hut had not solidified. The crystals were separated from* 
the liquid, washed, dried, and analysed. Their composition 
agreed approximately with the formula Na 2 S 2 0 3 , 2H 2 0. Other 
crystals having this composition were then obtained by driving off 
part of the water from fused crystals of the pentahydrate, and 
allowing the solution to cool. 
They were analysed by conversion into sodium sulphate. 
L— 1 *2186 gm. substance gave 0*9027 gm. Na 2 S0 4 = 24*02 per 
cent. Na. 
II. — 1*3977 gm. substance gave P0320 gm. Na 2 S0 4 = 23*95 per 
cent. Na. 
Calculated. Found. 
I. II. 
Na 2 S 2 0 3 , 2H 2 0. 23*74 % Na 24*02 % 23*95 %. 
In order to find out the temperature condition for the formation? 
of this hydrate, a solubility curve was constructed from the data 
given by Mulder * and by Kremers. f There appeared to be a 
change in the curve between 50° C. and 60° C., but the data were- 
insufficient to fix the temperature with accuracy. 
I therefore made a series of solubility determinations, extending: 
from 0° C. to 100° C. The form of apparatus used was that de- 
scribed by van’t Hoff.t The stirrer was driven at about 3000 re- 
volutions a minute by means of an electric motor ; and the 
* Damrner, Handbuch der Anorganischen Chemie , ii. b., 163. 
f Jaliresbericht , 1856, 275. 
Z Vorlesungen iiber bildung u. Spaltung yon Doppelsalzen, p. 54. 
