PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
21 
estimated as neutral sulphate of copper. The diffusion product of two experiments 
may be represented as follows, in grains : — 
Sulphate of copper . . 
I. 
. . . 0-81 
II. 
0*97 
Sulphate of ammonia 
. . . 5-46 
5-53 
627 
6-50 
The abundant formation and separation of sulphate of ammonia in these experi- 
ments, prove that the ammoniated sulphate 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 precipitating the lime entirely by carbonic acid gas and evaporating twice to 
dryness. Hydrate of potash, it will afterwards appear, is an eminently diffusive salt, 
having double the diffusibility 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 con- 
tinued. The salt diffused in the two cells amounted to 2’60 grs., of which 0’62 gr., 
or 23’85 per cent., was hydrate of potash. The chlorides of potassium and sodium, 
on the contrary, were not sensibly decomposed. 
It is known that a precipitation of sulphate of lime may occur, with a larger pro- 
portion of sulphate of potash in lime-water, in a close phial without external diffusion. 
As the decomposition of the sulphate of potash, in the latter case, has been referred 
to the insolubility of the sulphate of lime, so the decomposition in the former circum- 
stances is referred, in a similar sense, to the high diffusibility of hydrate of potash. 
7. Diffusion of Double Salts. 
How is the diffusion of two salts affected by their condition of combination as a 
double salt? A solution of the double sulphate of magnesia and potash, in the pro- 
portion of 100 water to 4 anhydrous salt, was operated upon in the four-ounce diffu- 
sion phials of T25 inch aperture, with a period of diffusion of seven days, at 57°’9 
Fahr. The diffusion product of the double salt was 8 09 and 7’81 grs. in two expe- 
riments : mean, 7*95 grs. 
The constituent salts, sulphate of magnesia and sulphate of potash, were now dis- 
