CHEMICAL SCIENCE. 223 



men under diffusion, diffused away from the latter as readily as from 

 their aqueous solutions, leaving the albumen behind in the phial. Urea 

 itself is as highly diffusible as chloride of sodium. In comparing the 

 diffusion of salts dissolved in ten times their weight of water, it was 

 found that isomorphous compounds generally had an equal diffusibility, 

 chloride-, of potassium corresponding with chloride of ammonium, ni- 

 trate of potash with nitrate of ammonia, and sulphate of magnesia 

 with sulphate of zinc. The most remarkable circumstance is, that 

 these pairs are equi-diffusive, not for chemically equivalent quantities, 

 but for equal weights simply. The acids differed greatly in diffusibil- 

 ity, nitric acid being four times more diffusive than phosphoric acid ; 

 but these substances also fell into groups, nitric and hydrochloric acids 

 appearing to be equally diffusive, as also acetic and sulphuric acids. 

 Soluble subsalts and ammoniated salts of the metals present a surpris- 

 ingly low diffusibility ; the quantities of the three salts, sulphate of 

 ammonia, sulphate of copper, and the blue ammonio-sulphate of copper, 

 diffused in similar circumstances, being very nearly as 8, 4, and 1. 

 When two salts are mixed in the solution-cell, they diffuse out into 

 the water atmosphere separately and independently of each other, ac- 

 cording to their individual diffusibilities. This is quite analogous to 

 what happens when mixed gases are diffused into air. An important 

 consequence is, that in liquid diffusion we have a new method of sep- 

 aration or analysis for many soluble bodies, quite analogous to the 

 separation of unequally volatile substances in the process of distilla- 

 tion. Thus it was shown that chlorides diffuse out from sulphates 

 and carbonates, and salts of potash from salts of soda ; and that from 

 sea-water the salts of soda diffuse out into pure water faster than the 

 salts of magnesia. The latter circumstances were applied to explain 

 the discordant results which have been obtained by different chemists 

 in the analysis of the waters of the Dead Sea, taken near the surface ; 

 the different salts diffusing up with unequal velocity into the sheet of 

 fresh water, v/ith which the lake is periodically covered during the 

 wet season. Prof. Graham has further shown, that chemical decom- 

 positions may be produced by liquid diffusion ; the constituents of a 

 double salt of so much stability as common alum being separated, and 

 the sulphate of potash diffusing in the largest proportion. In fact, the 

 diffusive force is one of great energy, and quite as capable of break- 

 ing up compounds as the unequal volatility of their constituents. 

 Again, one salt, as the nitrate of potash, will diffuse into a solution 

 of another salt, as nitrate of ammonia, as rapidly as into pure water ; 

 the salts appearing mutually diffusible, as gases are known to be. 



Lastly, the diffusibility of the salts into water, like that of the 

 gases into air, appears to be connected by simple numerical relations. 

 These relations are best observed when dilute solutions of the salts 

 are diffused from the solution-cell, such as 4, 2, or even 1 per cent, 

 of salt. The quantities diffused in the same period of seven days 

 from 4 per cent, solutions of the three salts, carbonate of potash, sul- 

 phate of potash, and sulphate of ammonia, were 10.25, 10.57, and 

 10.51 grains respectively; and a similar approach to equality was 

 observed in the 2 and 6 per cent, solutions of the same salt. It also 



