3kIR. T. GEAimi ON LIQUID DIFFUSION xiPPLIED TO ANALYSIS. 
193 
considered then as confined to the nine lower strata, and considerably resembles that of 
sugar in water for eight days. 
The difihsion of acetate of potash is still less advanced than that of iodine, and is 
probably confined to the six lower strata, the salt found in the higher strata presenting 
in its distribution the appearance of having been carried there by a movement of the 
fluid consequent upon heat-dilatation, and not by diffusion. The diffusion of acetate of 
potash in alcohol observed during seven days approximates to that of sugar in water 
during six days (Table IV.). 
I now proceed to observations of the simultaneous difiusion of two substances in the 
same fluid. The great object of this class of experiments was to separate salts of 
unequal difiusibility, and to test the application of diffusion as an analytical process. A 
mixture of two salts being placed at the bottom of the jar, it may be expected that the 
salts will diffuse pretty much as they do when they are diffused separately ; the more 
difiusive salt travelling most rapidly, and showing itself first and always most largely in 
the upper strata. The early experiments of diffusion from phials had shown indeed: 
that inequality of diffusion is increased by mixtiwe, and the actual separation is conse- 
quently gi'eater than that calculated from the relative diffusibilities of the mixed sub- 
stances. Chlorides of potassium and sodium diffuse nearly in the proportion of 1 to 
O’Sll, according to the earlier experiments. They may afford, therefore, the means of 
obseiuing the amount of separation that may be produced by a very moderate difference 
in difiusibility. A mixture of 5 grammes of each salt in the usual 100 cub. cent, of 
water was diffused. 
T.\ble VI. — Diffusion of a mixture of 5 per cent, of Chloride of Potassium and 5 per*- 
cent, of Chloride of Sodium, for seven days, at 12° to 13°. 
Xumber of stratum. 
Chloride of potassium. 
Cldoride of sodium. 
Total difiusate. 
1 
•018 
•014 
•032 
2 
•025 
•015 
•040 
3 
•044 
•014 
•058 
4 
•075 
•017 
•092 
5 
•101 
•034 
•1 35 
6 
•141 
•063 
•204 
7 
•185 
•104 
•289 
8 
•252 
•151 
•403 
9 
•330 
•212 
•542 
10 
•349 
•351 
•700 
11 
•418 
•458 
•8/6 
12 
•511 
•559 
1-070 
13 
•552 
•684 
1'236 
14 
•615 
•772 
1-387 
15 and 16 
1-385 
1-551 
2-936 
5-001 
4-999 
10-000 
In the upper part of the Table chloride of potassium always appears in excess, but 
not in so large a proportion in the first three strata as in the fourth. This inequality 
MDCCCLXI. 2 E 
