Prof. Graham on the Diffusion of Liquids. 259 



as possible in the proportion of 3 equivalents of acid to 1 of 

 base. As the Newcastle salt contained almost exactly half its 

 weight of water, the 3*40 grs. of anhydrous salt diffused out 

 are equivalent to 6*80 grs. of hydrated sulphate of alumina. 

 The sulphate of alumina appears thus to be more diffusive 

 than the double sulphate of alumina and potash, in the pro- 

 portion of 6*80 to 5*73. 



(3.) It was interesting to observe what really diffuses from 

 the ammoniated sulphate of copper (CuO, SO 3 , 2NH 3 + HO), 

 and to find if the low diffusibility of that salt is attended with 

 decomposition. The diffusion of the ammoniated sulphate of 

 copper was therefore repeated from a 4 per cent, solution in 

 the six-ounce solution phial, for eight days, at 64°*2 In eva- 

 porating the water of the jar afterwards, the ammoniated sul- 

 phate of copper present was necessarily decomposed, by the 

 escape of ammonia, and a subsulphate of copper precipitated. 

 The copper found, however, was estimated as neutral sulphate 

 of copper. The diffusion product of two experiments may be 

 represented as follows, in grains : — 



Sulphate of copper . . . 0*81 0'97 



Sulphate of ammonia . . 5 # 46 5*53 



6:27 6-50 



The abundant formation and separation of sulphate of am- 

 monia in these experiments, prove that the ammoniated sul- 

 phate of copper is largely decomposed in diffusion. 



(4.) Perhaps the most interesting result of this kind is a 

 solution which is given of the problem of the decomposition of 

 the alkaline sulphates by means of lime. 



Solutions were prepared of ^ per cent, of sulphate of potash 

 and of chlorides of potassium and sodium in lime-water. Two 

 solution phials were filled with each of these solutions, and 

 placed for diffusion in water-jars filled with lime-water, at 49°, 

 for seven days. 



In the sulphate no deposition of crystallized sulphate of 

 lime took place within the solution phial, while the water- 

 jar acquired an alkaline reaction, which remained after preci- 

 pitating the lime entirely by carbonic acid gas and evaporating 

 twice to dryness. Hydrate of potash, it will afterwards ap- 

 pear, is an eminently diffusive salt, having double the diffusi- 

 bility of sulphate of potash. The tendency of the former to 

 diffuse enables the affinity of the lime for sulphuric acid to 

 prevail, and the alkali is liberated and diffused away into the 

 external atmosphere of lime-water. By the latter, hydrate of 

 lime is returned to the solution cell and the decomposition 

 continued. The salt diffused in the two cells amounted to 

 2*60 grs., of which 0'62 gr., or 23*85 per cent., was hydrate 



S2 



