Harriry— Molecular Constitution of Supersaturated Solutions. 541 
a very small portion of it dissolved to form a blue solution. The 
white anhydrous salt could be seen in the solution, it became 
hydrated very slowly; finally hydration seemed to cease, and the 
white salt remained insoluble in the solution of CuSO,-5H.O 
which was formed. After a period of rest for two hours, this 
portion of the salt was seen to have become crystallized, and of 
a very pale blue colour. 
(2). 0°46 gr. was dropped into 5 c.c. of water at 15°C. The 
salt became hydrated, and dissolved to a clear blue solution in from 
five to ten minutes. 
(3). 0°46 gr. was dropped into 5 ¢.c. of a freshly prepared 
saturated solution of CuSO,-5H.O made with cold water. The 
anhydrous salt did not dissolve or appreciably diminish in volume 
and it remained white. Even after standing for four hours very 
few crystals were seen under the microscope; nearly all the salt 
had remained amorphous and anhydrous. 
(4). 0-46 gr. was added to 0°5 c.c. of cold water, shaken 
vigorously, poured into a watch-glass, and immediately examined 
under the microscope. ‘The amorphous white opaque masses of 
the anhydrous compound were seen to become the nuclei for well- 
formed minute crystals to grow out of, until they became crystal- 
line all through and transparent. It was observed that the solu- 
tion formed became turbid sometimes when this experiment was 
repeated in a test tube, and then crystals were deposited, as if a 
hydrated salt entered in solution, and afterwards separated as 
erystals containing probably a larger proportion of water. Hydra- 
tion, solution, and growth of crystals from the solution appears to 
be the order of the chemical change; while the formation of a 
liquid turbid from the separation of crystals indicates the pheno- 
menon of supersaturation. ‘Twenty-four hours after the last exam- 
ination of the amorphous solid and the crystals in experiment (8), 
the solid matter was examined again. The number of crystals 
had greatly increased ; they were small and appeared colourless. 
Someof the amorphous masses were semi-transparent and appeared 
of an extremely pale blue when drained from the cupric sulphate 
solution. <A few crystals of the normal salt CuSO,5H.O of much 
larger size, had grown, which had the usual appearance of such 
erystals. 
The semi-transparent masses were apparently compact groups 
