Prof. Graham on the Diffusion of Liquids. 273 



such a kind as to increase the real or apparent diffusion in 

 every one of them, or whether it is a peculiar character of this 

 little group, to which the ferricyanide of potassium, it will be 

 afterwards seen, falls to be added, while the ferrocyanide ap- 

 pears to belong to the other group : — 



Diffusion of 1 per cent, solutions at 58 0, 5. 



Chromate of potash .... 2*83 grs. 

 Bicarbonate of potash . . . 2'81 grs. 

 Bichromate of potash . . . 2*88 grs. 



The divergence from each other of two salts so closely iso- 

 morphous as sulphate and chromate of potash, in the propor- 

 tion of 100 to 105*2, is certainly remarkable, unless due to a 

 slight decomposition of the latter. 



(7.) Ferrocyanide and Ferricyanide of Potassium. 



Of these two salts the 1 per cent, solution only was diffused. 

 The time of diffusion was seven days, as usual ; the mean tem- 

 perature 54?°*5. In evaporating the liquid of the water-jars, 

 both salts were partially decomposed, so that it became neces- 

 sary to estimate the diffusion product by a determination of 

 the potash. Eight cells were employed for one salt and six 

 for the other, and the liquids of the water-jars evaporated two 

 together. 



The diffusion product of ferrocyanide of potassium (anhy- 

 drous) was 5*02, 5*22, 5'02 and 5*20 grs.; mean 5*12 grs., or 

 for one cell 2*56 grs. 



The diffusion product of ferricyanide of potassium was 5*54, 

 5'64> and 5*36 grs.; mean 5*51 grs., or for one cell 2*75 grs. 



Three cells of a similar solution of sulphate of potash which 

 were diffused for seven days at a mean temperature 1° lower, 

 or of 53°*5, gave 2*56, 2*53 and 2*62 grs.; mean for one cell 

 2*57 grs., a number which almost coincides with that of the 

 ferrocyanide of potassium (2*56 grs.). The ferricyanide of 

 potassium, on the other hand, is sensibly more diffusive, as 

 107' 6 to 100, and appears to rank with the bicarbonate and 

 bichromate of potash. The ferricyanide of potassium, again, 

 is a salt which probably undergoes a slight decomposition in 

 diffusion like those salts mentioned : — 



Diffusion of 1 per cent, solutions. 



Sulphate of potash .... 2*57 grs. at 53 0s 5. 

 Ferrocyanide of potassium . . 2*56 grs. at 54< 0, 5. 

 Ferricyanide of potassium . . 2*75 grs. at 54° # 5. 



The salts of the nitre class may also be compared in the 

 Phil. Mag. S. 3. Vol. 37. No. 250. Oct. 1850. T 



