Prof. Graham on the Diffusion of Liquids. 197 



The least soluble of the two salts appears in all cases to 

 have its diffusibility lessened in the mixed state. The ten- 

 dency to crystallization of the least soluble salt must evidently 

 be increased by the admixture. Now it is this tendency, or 

 perhaps more generally the increased attraction of the particles 

 of a salt for each other, when approximated by concentration, 

 which most resists the diffusion of a salt, and appears to 

 weaken the diffusive force in mixtures, as it is also found to 

 do so in a strong solution of a single salt. 



(4.) Equal weights of nitrates of potash and ammonia dis- 

 solved, as in certain preceding experiments, in five times the 

 weight of the mixed salts of water, and diffused for eight days, 

 gave in two experiments — 



At 59°- 4. At 52° 6. 



Nitrate of potash . . . 28*39 25*88 



Nitrate of ammonia . . 36*16 30*36 



64,-55 56*24 



The inequality in the diffusion of these two nitrates is sin- 

 gular, considering that in solutions of 1 salt to 10 water, they 

 appeared before to be equally diffusive. But on now com- 

 paring the diffusion of solutions of 1 salt to 5 water, at 52°*6, 

 the salts no longer diffused in equal proportions : — 



Nitrate of potash gave . 57*93 grs. 

 Nitrate of ammonia gave 82*08 grs. 



The solution of nitrate of potash last diffused was nearly a 

 saturated one, while that of nitrate of ammonia is far from 

 being so. The first has its diffusibility, in consequence, im- 

 paired, and falls considerably below the second. 



The relatively diminished diffusibility of sulphate of mag- 

 nesia, when associated with sulphate of water, is probably 

 connected with a similar circumstance; sulphate of magnesia 

 being less soluble in dilute sulphuric acid than in pure water. 



(5.) The salt which diffused from a strong solution of sul- 

 phates of zinc and magnesia, consisting of 1 part of each of 

 these salts in the anhydrous state and 6 parts of water, did 

 not consist of the two salts in exactly equal proportions. The 

 mixture of salts, diffused for eight days, as in the late experi- 

 ments, gave the following results : — 



Exp. I. 

 Sulphate of zinc . . 8*12 

 Sulphate of magnesia 8*68 



16*80 16*09 16*87 



There is therefore always a slight but decided preponde- 

 rance of sulphate of magnesia, the more soluble salt> in the 



II. 



HI. 



7*49 



8*12 



8*60 



8-75 



