CHEMICAL SCIENCE. 227 



diameter. The diameter of the tube being one-tenth of that of the mouth 

 of the bulb or disk of membrane exposed to the fluids, a rise of liquid in 

 the tube, amounting to 100 millimetres, indicated that as much water had 

 permeated the membrane and entered the osmometer as would cover the 

 whole surface of the membrane to the depth of one milllimctre, or one- 

 twenty- fifth part of an inch. Such millimetre divisions of the tube 

 become decrees of osmose, which are of the same value in all instruments. 



O * 



Osmose in membrane presented many points of similarity to that in 

 earthen ware. The membrane is constantly undergoing decomposition, 

 and its osmotic action is inexhaustible. Further, salts and other sub- 

 stances capable of determining a large osmose are all chemically active 

 substances, while the great mass of neutral monobasic salts of the metals, 

 such as chloride of sodium, possess only a low degree of action, or are 

 wholly inert. The active substances are also relatively most efficient in 

 small proportions. "When a solution of the proper kind is used, the 

 osmose or passage of fluid proceeds with a velocity wholly unprecedented 

 in such experiment. The rise of liquid in the tube with a solution con- 

 taining one-tenth per cent, of carbonate of potash in the osmometer was 

 167 degrees or millimetres ; and with one per cent, of the same salt, 206 

 degrees in five hours. With another membrane and stronger solution the 

 rise was 863 millimetres, or upwards of 30 inches, in the same time ; and 

 as much water therefore was impelled through the membrane as would 

 cover its whole surface to a depth of 8.6 millimetres, or one-third of an 

 inch. The chemical action must be different on the substance of the 

 membrane at its inner and outer surfaces to induce osmose ; and according 

 to the hypothetic view which accords best with the phenomenon, the 

 action on the two sides is not unequal in degree only, but also different in 

 kind. It appears as an alkaline action on the albuminous substance of 

 the membrane at the inner surface, and as an acid action on the albumen 

 at the outer surface. The most general empirical conclusion that can be 

 drawn is, that the water always accumulates on the alkaline or basic side 

 of the membrane. Hence, with an alkaline salt, such as carbonate or 

 phosphate of soda, in the osmometer and water outside, the flow is inwards ; 

 but with an acid in the osmometer, on the contrary, the flow is outwards, 

 cr there is negative osmose, the liquid then falling in the tube. In the last 

 case, the water outside is basic when compared with the acid within, and 

 the flow is therefore still towards the base. The chloride of sodium, 

 chloride of barium, chloride of magnesium, and similar neutral salts, are 

 wholly indifferent, or appear only to act in a subordinate to some other 

 active acid or basic substance, which last may be present in the solution 

 or membrane in the most minute quantity. Salts which admit of dividing 

 into a basic subsalt and free acid exhibit an osmotic activity of the highest 

 order. Such are the acetate and various other salts of alumina, iron and 

 chromium, the protochloride of iron, chloride of copper and tin, chloride 

 of copper, nitrate of lead, &c. The acid travels outwards by diffusion, 

 superinducing a basic condition of the inner surface of the membrane and 



