218 
PROFESSOR GRAHAM ON OSMOTIC FORCE. 
In the second and third experiments of the Table, the solutions were coloured 
distinctly blue, by means of the ordinary sulphate of indigo, without interfering much 
apparently with the osmose. 
The diffusates, when given, are as binacetate of alumina, and were calculated from 
the alumina found in the water-jar. 
In the last three observations of the one-tenth per cent, solution, the diffusate of 
salt is in proportion to the replacing water as 1 to 152, 131 and 137. 
In osmometer F of single membrane, acetate of alumina gave a diffusate not ex- 
ceeding one-third or one-fourth of the diffusate from sulphate of potash in similar 
circumstances. Thus, in three observations of the aluminous salt, the osmose was 
356, 393 and 397 ms., with the corresponding diffusates of 0‘ 102, O' 114 and 0 080 
gramme of binacetate of alumina; while two experiments on sulphate of potash, 
which were intercalated between the second and third of the preceding observations, 
gave diffusates of 0’325 and 0‘425 gramme of sulphate of potash. 
The osmose of acetate of alumina does not appear to be sensibly affected by pre- 
vious experiments made in the same membrane with sulphuric acid, but to fall 
greatly when an equal proportion of sulphate of potash is diffused along with the 
acetate of alumina. Of the following numbers, —4, 8, 7, 237, 7 and 18, the first 
th ree and the fifth, which are small, are the osmose of 0T per cent, sulphuric acid 
alone; the fourth, which is large, that of 1 per cent, of acetate of alumina, and the 
sixth that of 1 per cent, of acetate of alumina mixed with 1 per cent, of sulphate of 
potash, all in the same membrane. The diffusate of the pure acetate of alumina was 
0'087 gramme, which is low for a 1 per cent, solution, as compared with the diffusates 
from the one-tenth per cent, solutions of sulphuric acid, which were 0’039, 0 - 042, 
0‘046 and 0‘044 gramme of sulphuric acid. 
The addition of an equal weight of chloride of sodium to the one per cent, solution 
of acetate of alumina, lowered the osmose of the latter salt, in osmometer F, from 397 
to 267 ms. This is a small amount of interference compared with that exercised by 
the sulphate of potash in the same membrane. 
Pure binacetate of alumina was found to be largely decomposed when diffused in 
open vessels, the acetic acid escaping and leaving behind the allotropic soluble 
alumina of Mr. Crum. This last substance is remarkable for its low diffusibility, 
but this subject will require further discussion on a future occasion. 
Iron. — Protosulpliate of Iron. This salt appeared, like sulphate of magnesia, to 
exhibit only the exchange by diffusion of one part of salt for five or six parts of 
water ; the rise of fluid in the osmometer also increasing pretty uniformly with the 
proportion of salt. Thus, in double membrane of good resistance, 1 per cent, of this 
salt (always supposed anhydrous) gave 21 and 30 ms. ; 4 per cent. 60 and 84 ms., at 
a temperature between 61° and 64°Fahr. 
Protochloride of Iron . — This salt separates itself from some other magnesian chlo- 
rides, and gives rise to a positive chemical osmose, which is considerable in amount. 
