PROFESSOR GRAHAM ON OSMOTIC FORCE. 
187 
brane, observed by M. Matteucci and others, depends often, I believe, upon the 
soluble matter of the muscular coat being thrown outwards or inwards, according as 
the membrane is applied. The muscular coat was on this account removed from the 
ox-bladder employed, and the serous membrane remaining found to acquire greatly 
increased activity, and also to act with much greater regularity in successive experi- 
ments. The membrane so prepared could be used for weeks together without the 
slightest putrescence of any part of it. Two of these thin membranes, or a double 
membrane, was often applied. The weight of a disc of single membrane, \\ inches in 
diameter in a dry state, varied from about 0'5 to T2 gramme. The soundness of the 
membrane of an osmometer and its degree of permeability were always roughly tested 
before an experiment, by filling the bulb, without its tube, completely with water, 
hanging it up in air, and observing how frequently a drop fell from the instrument. 
The time between each drop varied, with suitable membranes, from one to twenty 
minutes. The times in which water permeated the same membranes by osmose 
varied between much narrower limits, perhaps from one to two. 
The quantity of salt which traversed different membranes by diffusion, was also 
found to be in proportion to the osmotic permeability of the membranes, and not 
to their mechanical porosity. 
To wash the membranes, they were macerated in distilled water after every expe- 
riment for not less than eighteen hours, without being ever removed from the glass 
bulb. A membrane also was never allowed to dry, but was kept humid as long as 
it was in use for experiments. 
Osmose in membrane presented many points of similarity to osmose in earthenware. 
The membrane was constantlyundergoing decomposition, soluble organic matter being 
found both in the fluid of the osmometer and in the water of the outer jar after every ex- 
periment; and the action of the membrane appeared to be exhaustible, although in avery 
slowand gradual manner. Those salts and other substances, of which a small proportion 
is sufficient to determine a large osmose, are, further, all of the class of chemically active 
substances, whilethe great mass of neutral organic substancesand perfectly neutral mono- 
basicsalts of the metals, such as the alkaline chlorides, possess only a low degree of action. 
When a solution of the proper kind is used in the osmometer, the passage of fluid 
proceeds with a velocity wholly unprecedented in such experiments. Take, for 
instance, the rise in five hours exhibited in a series of experiments upon solutions of 
several different proportions of carbonate of potash, made in succession with the same 
membrane in the order in which they are related. 
With O’ l per cent, carbonate of potash, a rise of 182 ms. 
With 0'1 per cent, carbonate of potash, a rise of 120 ms. 
With 0T per cent, carbonate of potash, a rise of 199 ms. 
With 0’5 per cent, carbonate of potash, a rise of 246 ms. 
With 0’5 per cent, carbonate of potash, a rise of 194 ms. 
With 1 per cent, carbonate of potash, a rise of 205 ms. 
With 1 per cent, carbonate of potash, a rise of 207 ms. 
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