14 
PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
4. Diffusion of Mixed Salts. 
When two salts can be mixed without combining, it is to be expected that they will 
diffuse separately and independently of each other, each salt following its special 
rate of diffusion. 
(1.) Anhydrous sulphate of magnesia and sulphate of water (oil of vitriol), one 
part of each, were dissolved together in 10 parts of water, and the solution allowed 
to diffuse for four days at 61°'5. 
The water-jar was found to have acquired — 
Sulphate of magnesia . . . o‘60 grs. 
Sulphate of water .... 2T92 grs. 
27‘52 grs. 
The experiment with the same diffusion cell and liquid being continued for a 
second period, this time of eight days, there was found to be simultaneously dif- 
fused, of — 
Sulphate of magnesia . . . 9‘46 grs. 
Sulphate of water .... 29‘32 grs. 
3878 grs. 
It is obvious that the inequality should be greatest in the first period of diffusion, 
or with the initial diffusion, as it actually appears above, and become less and less 
sensible as the proportion of the low diffusive salt comes to be increased in the solu- 
tion phial. 
In former experiments upon the solution of sulphate of magnesia alone in water, 
as 1 salt to 10 water, compared with sulphate of water, also as 1 to 10, the disparity 
in the diffusion of these two salts was less considerable, being only as 1 to 2'385, 
instead of 1 to 3 or 4. 
(2.) A solution was also diffused of 1 part of anhydrous sulphate of soda and 1 part 
of chloride of sodium in 10 parts of water, for four days at 61°'5. The salt which 
diffused out in that time consisted of — 
Sulphate of soda 9‘48 grs. 
Chloride of sodium .... 17‘80 grs. 
27'28 grs. 
The sulphate of soda in the last experiment had begun to crystallize in the solu- 
tion phial, from a slight fall of temperature, before the diffusion was interrupted, a 
circumstance which may have contributed to increase the inequality of the propor- 
tions diffused of these two salts. 
(3.) A solution of equal weights of anhydrous carbonate of soda and chloride of 
sodium, namely, of 4 parts of the one salt and 4 parts of the other, to 100 water, was 
diffused from 3 four-ounce phials of 1-25 inch aperture, at a mean temperature of 57°‘9 
and for seven days. The diffusion product amounted to 17 ' 10 , 17-58 and 18-13 grs. 
