374 Scientific Intelligence.— Chemistry. 
mosphere, for the phenomenon is retarded as well by covering the 
solution with spirits of turpentine, which preserves it from contact 
with the air, as by keeping it in a vacuum; and he has proved also, 
that the solvent powers of water are quite inalopendeale of pressure on 
its surface. Likewise when crystallization fails, as is sometimes the 
case when the atmosphere is admitted, no advantage is gained by 
adding to its pressure. This distinguished chemist was inclined to 
the opinion, that the crystallization might be owing to the diminution 
of solvent power, occasioned by the absorption of air. This opinion 
is strengthened by the experiments of Mr. Graham. By placing the 
hot solution of sulphate of soda in a tube, and inverting it in the mer- 
curial bath, having previously heated the mercury, to prevent crystal- 
lization from a rapid cooling of the solution, he ascertained, by 
throwing up bubbles of air of different kinds, that their inflaence in 
determining crystallization, i is precisely proportional to their degree of 
solubility in water, and in saline solutions: Thus a bubble of car- 
bonic acid is more powerful than common air, and a bubble of am- 
moniacal gas or sulphurous acid, has more effect than carbonic acid. 
With ammoniacal gas, the crystallization follows the ascent of the 
bubble so rapidly, that the latter sometimes becomes imprisoned 
among the crystals before it reaches the top of the tube. Hydro- 
gen, on the other hand, and other gases less soluble in water than 
common air, have decidedly less effect. A very small quantity of a 
liquid, soluble in water, causes the solution immediately to crystal- 
lize, as may be evinced by using alcohol: now, it is well known that 
alcohol precipitates sulphate of soda dissolved in water, and. the solu- 
ble gases appear to possess a similar property. 
‘The enlargement of volume, which ensues upon the sudden crys- 
tallization of sulphate of soda, the author ascribes altogether. to the 
expansive effect of the heat thus developed. 
., The various influence of the different gases is an important fact, 
not. before remarked ; but is it sufficient to demonstrate completely 
the. explanation coeaget by Mr. Graham? We think not, and, we 
are of opinion that the phenomenon which sulphate of soda presentSy 
: belongs to that class of facts, which, though still small, is constantly 
increasing, and which, isolated thus far in the partial explanation 
which each one of them has received, constitute, in their totality, that 
molecular Sans still so very imperfectly understood, and so 
. eeaiente std D.L.R. Bib. Univ. Juin, 1829 
