Prof. Graham on the Diffusion of Liquids. 279 



for two cells, 3*55, 3*63, 3*33 and 3*51 grs. ; mean for two 

 cells, 3*50 grs. 



Sulphate of potash diffused for 4*95 days, at 47°'3, gave for 

 two cells, 3*54-, 3*31, 3*51 and 3*63 grs.; mean for two cells, 

 3*50 grs., or exactly the same as for nitrate of potash above. 



(b.) Nitrate of potash diffused for seven days, at 48°*6, gave 

 6*1, 6*2, 5*9 and 5*92 grs.; mean for two cells, 6*04 grs. 



Sulphate of potash diffused for 9*9 days, at 49°*1, gave 

 6*13, 5*92, 6*18 and 6*59 grs.; mean 6*20 grs., or, excluding 

 the last experiment, 6*08 grs. 



Chromate of potash diffused also for 9'9 days, at 49°*1, gave 

 6*19, 6*18, 6*40 and 6*38 grs.; mean for two cells, 6*29 grs. 

 The diffused chromate presented no appearance of decompo- 

 sition on this occasion. 



(c.) Nitrate of potash diffused for 10*5 days, at 48°, gave 

 8*36, 8*95, 8*82 and 8*84 grs. ; mean for two cells, 8*74 grs. 



Sulphate of potash diffused for 14*85 days, at 48°*6, gave 

 8-99, 8*94, 8*66 and 8*56 grs.; mean for two cells, 8*79 grs. 



The mean results for the three different sets of periods of 

 diffusion are as follows : — 



3-5 and 4*95 /Nitrate of potash, at 47°'2, 3*50 grs. 100 



days \Sulphate of potash, at47°'3, 3*50 grs. 100 



[Nitrate of potash, at 48°*6, 6*04 grs. 100 



7 and 9*9 daysj Sulphate ofpotash, at 49°*1, 6*20 grs. 102*65 



[_ Chromate ofpotash, at 49°*1, 6*29 grs. 104*14 



10*5 and 14*85 /Nitrate of potash, at 48°, 8*74 grs. 100 



days \Sulphate of potash, at 48°*6, 8*79 grs. 100*57 



The concurring evidence of these three series of experi- 

 ments appears to be quite decisive in favour of the assumed 

 relation of 1 to 1*4142, between the times of equal diffusion 

 for the nitrate and sulphate of potash, and consequently of the 

 times for the two classes of potash salts, of which the salts 

 named are types. The same experiments are also valuable as 

 proving the similarity of the progression of diffusion, in two 

 salts of unequal diffusibility. I shall return again to the rela- 

 tion between nitrates and sulphates, under the salts of soda. 



(8.) Hydrate of Potash. 



(1.) Eight cells of the 1 per cent, solution of pure fused 

 hydrate ofpotash were diffused for seven days in the vault, 

 with a temperature ranging only from 59° to 58°, of which 

 the mean was 58°*6. The product of four cells evaporated 

 together was 17*57 grs. of hydrate ofpotash, and of the other 

 four cells 17*19 grs. ; mean 17'38 grs., or 4*345 grs. for one 

 cell. The hydrate of potash was estimated from the chloride 



