Fluids of a different nature have, with refer ence to endosmosis, properties which are in no way in proportion to their respective densities. Thus sugar-water and gum-water of the same density, being put successively into the same endosmometer, which is- plunged into pure water, the former produces the endosmosis with a velocity as 17, and the latter with a velocity as 13 only. I have seen, in the same manner, a solution of hydrochlorate of soda and a solution of sulphate of soda of the same density, put successively in the same endosmo meter surrounded with pure water; the velo city of the endosmosis produced by the solu tion of sulphate of soda is exactly double that of the endosmosis produced by the solution of hydrochlorate of soda. These results are inva riable, and I ant persuaded that if I have ever obtained a different result, the experiment has been defective.
I have made several experiments since with gelatinous and albuminous waters placed suc cessively in the same endosmometer, surround ed with pure water, which produced endos mosis severally in the proportion of 1 to 4 ; so that the albumen had four times more power of endosmosis than the gelatine. I have seen by another experiment that the power of en dosmosis of syrup is to the power of endos mosis of albuminous water of the same den sity, as 11 is to 12.
All alkalies and soluble salts produce en dosmosis; so do all acids, but each with spe cial phenomena, which will be noticed by and by. These chemical agents in general occasion an endosmosis of short duration only, when the endosmometer is closed with a portion of an animal membrane. Organic fluids alone, which are not very sensibly either acid or alkaline, Or salt, produce lasting endosmosis, which, in deed, does not stop until the fluids are altered by putrefaction, when they become charged with sulphuretted hydrogen. I have shown that when an endosmometcr is closed with a thin plate of baked clay instead of the animal mem brane, the endosmosis which a saline solution produces, and which would have stopped in a few hours with the animal membrane, continues to go on indefinitely with the baked clay.
The property of destroying endosmosis may be considered as belonging to all chemical re agents, but merely on account of their sus ceptibility to enter into combination with the permeable partition of the endosmometer. Thus all acids, alkalies, soluble salts, alcohol, &e. being disposed to combine with the elements of organic membranes, destroy endosmosis, al though) they had induced it before their complete combination with the elements of the membrane had taken place ; and it is not until this combi nation is complete that endosmosis ceases. Or ganic fluids,which have no chemical action upon the elements of the membrane of the cndosmo meter, ought not, consequently, to tend to the destruction of endosmosis, unless some change should take place which should give them a chemical action, such as they usually acquire by decomposition, when they usually become charged with sulphuretted hydrogen.
My earlier experiments tended to show that carbonate of lime (Omar carbonatic) reduced to thin lamina, and employed to close an en dosmometer, is totally without the power of producing endosmosis; my latter experiments have somewhat modified this conclusion. After having vainly employed lamina of carbonate of lime of greater or less thickness, I finished by making use of one of white marble, two millimetres in thickness, but with no better success. Without carrying my experiments further, I concluded that porous carbonate of lime was totally unapt to excite endosmosis.
This conclusion having, notwithstanding, left some doubts in my mind, I again took the same plate of marble with the intention of measuring its permeability to water, compared with the various degrees of thickness which I could give it, and of renewing, at the same time, my at tempts to make it produce endosmosis. I laving closed an endosmometer with this plate of mar ble, I filled the reservoir and the tube of the instrnmcnt with pure water, and suspended it over a vessel filled with water,in which the plate of marble only was immersed. If the marble had been permeable to water, the fluid con tained in the endosmorneter would have flowed through the capillary conduits of the plate, and this flow would have become perceptible by the sinking of the water in the tube, the inte rior of which was only two millimeters in dia meter.
The result of this experiment was that the plate of marble, which was four centimeters in diameter, did not lose by filtration, in one day, more than the small quantity of water capable, by its subtraction, of lowering its level one millimeter and a half in the tube. I next tried syrup in this endosmometer, the reservoir being plunged into pure water ; but sso endosmosis was induced. I now reduced the thickness of the plate of marble to one millimeter and a half; in this state it lost by filtration, in the course of a day, eleven mil limeters of water measured by the tube. The ,permeability of this plate was, as may be per ceived, very sensibly increased : still the en dosmometer which it closed when filled with syrup showed no indications of endosmosis. 1 reduced the thickness of the plate of marble to one millimeter. In this state it lost by fil tration, in the space of a day, twenty-one milli meters of water measured in the tube. I put into the endosmometer, which this plate of marble closed, the same syrup which had been used in the preceding experiments, and the density of which was 1.12, and I now ob tained an endosmosis which manifested itself by an ascension of seven millimeters in four and-twenty hours. This last experiment proved to me that carbonate of lime was not, as I had hitherto found it, totally without the power to produce endosmosis. I wished to compare this plate of marble with a piece of bladder of the same surface under the double point of view, of their permeability, and their respec tive properties of producing endosmosis. Having therefore taken off the plate of marble which closed the endosmometer, I replaced it by a piece of bladder whose permeability to water I measured in the same manner as above. I found this permeability very nearly equal to that of the plate of marble of one millimeter in thick ness. I then put into this endosmometer some syrup similar in density to that which I had used in the same endosmometer closed with the plate of marble. The endosmosis which I obtained raised the syrup seventy-three millimeters in three hours. Thus the permea bility to water being equal in the bladder and in the plate of marble, the endosmosis pro duced by the first was to the endosmosis pro duced by the second as 584 is to 7, a most extraordinary difference, and difficult to be accounted for. These experiments prove that carbonate of liine is but very little apt to pro duce endosmosis, in which it differs singularly from baked clay, thin lamina; of which are almost as apt to produce endosmosis as organic membranes.