208 
PROFESSOR GRAHAM ON OSMOTIC FORCE. 
riment, and that the osmose falls off pretty regularly to the fifth experiment (268 ms.). 
The change in the aeration of the solution in the second and third experiments can- 
not be said to interfere with this progression. The influence of free oxygen on the 
membrane is not therefore indicated as a cause of osmose. It may be added, that the 
converse experiment of depriving the fluid of the water-jar of air by boiling, led also 
to a negative result. It will be remembered, further, that the osmose of oxalic acid 
was not interfered with by an addition of sulphurous acid, which was likely to coun- 
teract the action of oxygen, if such an action existed in osmose. 
When phosphate of soda is substituted for carbonate of potash, both 1 per cent., 
the osmose declines from 268 to 176 ms. The phosphate of soda being repeated, the 
osmose rises a little, namely to 194 ms. The one-tenth per cent, solution of the 
same salt which follows, maintains here the considerable osmose of 196 and 190 ms. 
On returning again to the application of carbonate of potash in the instrument, the 
osmose gradually rises and regains 335 ms. for the 1 per cent, solution of that salt. 
From these repetitions of osmose it may be inferred, that whatever be the nature 
of the chemical action on membrane which prompts osmose, that action is by no 
means of a rapidly exhaustible character. 
It may be added, with regard to the osmotic action of extremely dilute solutions 
of carbonate of potash, that the osmose is lowered rapidly in proportions below one- 
tenth of a per cent, of that salt. The osmose of O’Ol per cent, of carbonate of potash, 
in double membrane, amounted only to 19, 23 and 17 ms. in three successive ex- 
periments. The osmotic action of carbonate of potash must, therefore, be inferior 
to that of hydrate of potash in the extreme degrees of dilution. 
In the experiments of the preceding series, the influence of a salt often appears not 
to terminate with its presence in the osmometer, but to extend to following experi- 
ments made with other salts, or made with different proportions of the original salt. 
If this arises from portions of the first salt remaining in the membrane, they must be 
portions which are not easily washed out. The substance of membrane may possibly 
have an attraction for highly osmotic salts, capable of withdrawing small quantities 
from solution. When the membrane, however, is removed from the osmometer, 
after such experiments as are referred to, slightly washed and then incinerated, 
only minute traces of the salt last used are commonly discovered; if indeed the salt 
has not entirely disappeared. 
Phosphate and Carbonate of Soda . — The osmose of the carbonate of soda appears 
to be quite similar to that of carbonate of potash. A considerable amount of informa- 
tion respecting the two soda salts named is conveyed in the following series of 
experiments, which includes also observations on the serum of ox-blood. 
