Grams of Na 2 S 2 0 3 in 100 gm. water. 
250 Proceedings of Royal Society of Edinburgh. [sess. 
Large quantities of pure dihydrate were prepared in the follow- 
ing way : — Pure recrystallised sodium thiosulphate was dried over 
sulphuric acid in a vacuum desiccator. The anhydrous salt so 
obtained was dissolved in fused pentahydrated salt, and the 
solution kept at 53° C. Crystallisation was induced by adding 
Temper ature. 
a few fragments of the dihydrate to the solution. The crystals 
were removed from the liquid, placed in an oven at 53° C. on 
filter-paper, and covered over with glass to prevent loss of water. 
They were quite clear and transparent. The analysis, carried out 
as in the solubility determinations, agreed closely with the formula. 
I. — 2 *3651 gm. substance gave P9163 gm. ]STa 2 S 2 0 3 = 8P03 
per cent. 
