34 
PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
It is interesting to observe how the chlorate of potash rises in the lower proportions 
and approaches to the normal rate of its class. The dilfusion products of all the salts 
are obviously more uniform for the two than for the 4 per cent, solutions, and again 
more uniform for the 1 than for the 2 per cent, solutions. The extremes in the 1 per 
cent, solutions are 3'66 grs. chlorate of potash, and 3'89 grs. chloride of ammonium, 
which are as I to 1’0628. We have here an approach to equality in diffusion, which 
appears to be as close as the experimental determinations are of the specific heat of 
different bodies belonging to one class. The numbers for the specific heat of equi- 
valents of the metallic elements are known to vary as 38 to 42. 
The salts of potash thus appear to fall into two groups of very similar if not equal 
diffusibility. What is the relation between these groups? 
The diffusion of 4 per cent, solutions of carbonate and nitrate of potash was 
repeated at a temperature rising gradually from 63° to 65° during the seven days of 
the. experiment, with a mean of 64°']. The diffusion products of the carbonate were 
10'31, 10'05 and 10'44 grs. in three cells; mean 10'27 grs. Of the nitrate, 13’98, 
13'86 and 13'60 grs. ; mean 13'81 grs. We have thus a diffusion in equal times of— 
Carbonate of potash . 10'27 1 
Nitrate of potash . . 13'81 1*3447 
These experiments are almost identical with the former results, 10*25 carbonate of 
potash, and 13*97 nitrate of potash. 
But the numbers thus obtained cannot be fairly compared, owing to the diminishing 
progression in which the diffusion of a salt takes place. Thus when the diffusion of 
nitrate of potash was interrupted every two days, as in a former experiment with 
chloride of sodium, the progress of the diffusion for eight days was found to be as 
follows in a 4 per cent, solution, with a mean temperature of 66°. 
Nitrate of Potash. 
Diffused in first two days . 
Diffused in second two days . 
Diffused in third two days 
Diffused in fourth two days . 
4*54 grs. 
4*13 grs. 
4*06 grs. 
3*18 grs. 
15*91 
The absence of uniformity in this progression is no doubt chiefly due to the want 
of geometrical regularity in the form of the neck and shoulder of the solution phial. 
A plain cylinder, as the solution cell, might give a more uniform progression, but 
would increase greatly the difficulties of manipulation. 
The diffusion of carbonate of potash will no doubt follow a diminishing progression 
also ; but there is this difference, that the latter salt will not advance so far in its 
progression, owing to its smaller diffusibility, in the seven days of the experiment, as 
the more diffusible nitrate does. The diffusion of the carbonate will thus be given 
