220 Mr. T. Graham on Liquid Diffusion applied to Analysis, 



of separation. But if the acids arc unlike in diffusibility, the 

 case is not so clear. If, for instance, the potassium were in the 

 form of chloride and the sodium in that of sulphate, might not 

 the diffusion of the potassium be promoted by the highly diffusive 

 chlorine with which it is associated, and the diffusion of the soda, 

 on the other hand, be retarded by its association with the slowly 

 diffusive sulphuric acid? Will, in fine, the separation of the 

 metals be greater from a mixture of chloride of potassium and 

 sulphate of soda, or even from sulphate of potash and chloride of 

 sodium, than from the two chlorides or from the two sulphates ? 

 The inquiry, it will be remarked, raises the whole question of 

 the distribution of acid and base in solutions of mixed salts. It 

 will be illustrated by a comparison of the diffusion of chloride of 

 potassium mixed with sulphate of soda, with the diffusion of sul- 

 phate of potash mixed, with the chloride of sodium, the salts being 

 taken in equivalent proportions. 



Table IX. — Diffusion of a mixture of 5*12 per cent, of Chloride 

 of Potassium and 4*88 per cent, of Sulphate of Soda (equiva- 

 lent proportions), for seven days, at 14°. 



No. of stratum. 



Potassium, 



Sulphuric acid, 



Total diffusate, 



in grammes. 



in grammes. 



m grammes. 



1 



•028 



•002 



•024 



2 



•035 



•002 



•030 



3 



■048 



•004 



•045 



4 



•064 



•009 



•066 



5 



•092 



•016 



•097 



6 



•128 



•032 



•149 



7 



•174 



•058 



•215 



3 



•242 



•105 



•316 



9 







•441 



10 







•615 



11 







•815 



12 







1-042 



13 







1-290 



14 







1-517 



15 and 16 









3-346 









10-008 



The weight of the mixed salt was always 10 grammes. The 

 diffusions exhibited in Tables IX. andX. are strikingly similar,and 

 indeed may be considered as identical. It thus appears that the 

 diffusion of the metals is not affected by the acid with which they 

 are in combination. The result is quite in harmony with Ber- 

 thollet's view, that the acids and bases are indifferently combined, 

 or that a mixture of chloride of potassium and sulphate of soda 

 is the same thing as a mixture of sulphate of potash and chloride 



