184? Prof. Graham on the Diffusion of Liquids. 



In other experiments where the liquid in the upper bottle 

 was a solution in water of nitrous oxide gas, instead of pure 

 water, the carbonic acid of the lower bottle was also observed 

 to diffuse into the liquid above it, as freely as it did into pure 

 water in a comparative experiment; the ultimate ratios being 

 1 to 0*12 in the nitrous oxide liquid, and 1 to 0*10 in the water 

 experiment. 



With the necks of the pair of bottles occupied by sponge 

 charged with distilled water, the diffusion of the carbonic acid 

 of the lower bottle proceeded with little change in its rapidity, 

 or in the result when nitrous oxide was placed above it. The 

 carbonic acid found in the upper bottle, and which had dif- 

 fused into it from the lower, was 0*231 when the upper bottle 

 contained water alone, and 0*229 when it was water charged 

 with three- fourths of its volume of nitrous oxide gas, — to 1 

 carbonic acid remaining undiffused in the lower bottle in both 

 cases. 



It appeared, then, that the liquid diffusion of carbonic acid 

 was a slow process compared with its gaseous diffusion, quite 

 as much as days are to minutes. 



That this diffusion of the liquid carbonic acid takes place 

 with undiminished vigour into water already saturated with 

 nitrous oxide, the substance of all others most resembling 

 carbonic acid in solubility and the whole range of its physical 

 qualities. The diffusion of the liquid carbonic acid appears 

 no more repressed by the liquid nitrous oxide, than the diffu- 

 sion of gaseous carbonic acid is by gaseous nitrous oxide. 



But the chief interest of these observations was the practical 

 solution which they give to the question, whether, in conduct- 

 ing experiments on liquid diffusion, accidental causes of dis- 

 turbance and intermixture of two liquids, communicating 

 freely with each other, can be avoided. It was made evident 

 that little is to be feared from accidental dispersion when or- 

 dinary precautions are taken. 



An excess of density in the lower liquid of not more than 

 ToW*-* 1 P art * s f° un( l adequate to prevent any considerable 

 change of place of the latter, — from expansion by heat, acci- 

 dental tremors and such disturbing causes, which must exist, 

 — for days together. 



(2.) Another early inquiry was, how far is the diffusion of 

 various salts governed or modified by the density of their so- 

 lutions. 



Solutions of eight hydrated acids and salts were prepared, 

 having the common density of 1*200, and were set to diffuse 

 into water in the following manner: — 



Eighteen or twenty six-ounce phials were made use of to 



