194 
ME. T. GEAHAM ON LIQUID DIEEUSION APPLIED TO ANALYSIS. 
may be partly owing to mechanical dispersion of the mixed solution, but is to be 
referred chiefly, I believe, to errors of analysis from a loss of the chloride of potassium 
difficult to avoid in the determination of minute proportions of that salt by means of 
chloride of platinum. Of 92 milligrammes of salt found in the fourth stratum, 75 mil- 
ligrammes, or 81 ‘5 per cent., are chloride of potassium. The first six strata contain 
together 5.61 milligrammes, of which 404 milligrammes, or 72 per cent., that is nearly 
three-fourths, are chloride of potassium. We have to descend to the tenth stratum 
before the salts are found in equal proportions. The progression is then inverted, and 
chloride of sodium comes to preponderate in the lower strata. 
It is evident that the preceding experiment might be so conducted as to diffuse away 
the chloride of potassium and leave below a mixture containing chloride of sodium in 
relative excess, to as great an extent as the chloride of potassium is found above, in the 
last experiment. 
Further, the mixture in which chloride of potassium was concentrated in the experi- 
ment described, so as to form 72 per cent, of the whole mixture, might be subjected 
again to diffusion in the same manner. In an experiment upon a mixture of 7 '5 
grammes of chloride of potassium and 2-5 grammes of chloride of sodium, the sis 
upper strata gave 640 milligrammes of salt, of which 610 milligrammes, or 95-3 per 
cent., were chloride of potassium. It is obwous that by repeating this diffusive recti- 
fication a sufficient number of times, a portion of the more diffusive salt might be 
obtained at last in a state of sensible purity. 
The preceding example illustrates the separation of unequally diffusive metals or 
bases ; the following example, on the other hand, the separation of unequally diffusive 
acids united with a common base. Chloride of sodium and sulphate of soda diffuse 
separately in the phial experiments in the proportion of 1 to 0-707. 
Table VII. — Diffusion of 5 per cent, of Chloride of Sodium and 5 per cent, of 
anhydrous Sulphate of Soda, for seven days, at 10° to 10°-75. 
Number of stratum. 
Chloride of sodium, 
in grammes. 
(Sulphate of soda, 
in grammes. 
Total difFusate, 
in grammes. 
1 
•009 
•009 
2 
•013 
•001 
•014 
3 
•024 
•002 
•026 
4 
•038 
•003 
•041 
5 
•060 
•006 
•066 
6 
•095 
•012 
•107 
7 
•141 
•029 
•170 
8 
•203 
•059 
•262 
9 
•278 
•115 
•393 
10 
•360 
•205 
•565 
11 
•473 
•317 
•790 
12 
•560 
•507 
1-067 
13 
•637 
•694 
1-331 
14 
•718 
•909 
1-627 
15 and 16 
1-390 
2-141 
3-531 
4-999 
5-000 
9-999 • 
