280 Prof. Graham on the Diffusion of Liquids, 



of potassium which it gave when saturated with hydrochloric 

 acid. The diffusion product of sulphate of potash for seven 

 days, at 58°*5, or almost the same temperature, was 10*75 grs. 

 for the four cells, as already stated, and consequently 2*64 grs. 

 for one cell. It thus appears that the hydrate of potash is 

 greatly more diffusive than the sulphate of potash in the same 

 period of seven days, namely, as 4*345 to 2*64. Such a re- 

 sult indeed is not inconsistent with the times of equal diffusion 

 of these two substances, differing as much as I to 2. 



(2.) Of pure fused hydrate of potash, a 1 per cent, solution 

 was diffused from four cells for 4*95 days at a mean tempera- 

 ture of 53°*7, against a 1 per cent, solution of nitrate of potash 

 in six cells, for seven days, at a mean temperature 0°*1 lower, 

 or of 53 0, 6. The hydrate of potash which diffused, is calcu- 

 lated as before from the chloride of potassium which it gave, 

 when neutralized by hydrochloric acid. Hydrate of potash 

 diffused from two cells 5"97 and 6*28 grs.; mean 6*12 grs., 

 or 3*06 grs. for a single cell. 



Nitrate of potash diffused from two cells 6*22, 6*54 and 

 5*93 grs.; mean Q*23 grs., or 3*11 grs. for a single cell. The 

 diffusion of nitrate of potash being 100, that of the hydrate of 

 potash is 98*2, numbers which are sufficiently in accordance. 

 But the times were as I to 1*4142, and their squares as 1 to 2. 

 So far then as this series of experiments on hydrate of potash 

 entitles us to conclude, we appear to have for the salts of pot- 

 ash a close approximation to the following simple series of 

 squares of equal diffusion times : — 



Squares of Times of Equal Diffusion, or Solution Densities, 



Hydrate of potash . . * 1 



Nitrate of potash .... 2 



Sulphate of potash ... 4 



(3.) The hydrate of potash was also diffused at the lower 



temperature, 39°*7, in company with the nitrate and sulphate 



of potash for a period of 6*364 days (six days, eight hours, 



forty-four minutes). 



The 1 per cent, solution of hydrate of potash gave in eight 

 cells, evaporated two together, 6*93, 6*93, 6*93 and 6*89 grs.; 

 mean 6*92 grs. 



The 2 per cent, solution of hydrate of potash gave in three 

 single cells, 6*77, 6*49 and 7*10 grs.; mean 6*79 grs. 



The diffusion of nitrate of potash in nine days at the same 

 temperature, as already detailed, was sensibly the same, or 

 6*83 grs. for both the 1 and 2 per cent, solutions. The times 

 for the two salts were as 1 to 1*41 42. 



The diffusion of hydrate of potash, at 39°*7, may therefore 



