Royal Socieiy, 153 



gas and water at the negative pole, causing the accumulation of water 

 observed there, while the oxygen alone proceeds in the opposite direc- 

 tion to the positive pole. Attention was also called to the fact that 

 acids, and alkalies, when in solution, are chemically combined with 

 much water of hydration, sulphuric acid for instance evolving heat 

 when the fiftieth equivalent of water is added to it. In the combi- 

 nation of such bodies, the disposal of the water is generally over- 

 looked. Osmose was considered as depending upon such secondary- 

 results of combination, that is, upon the large number or volumi- 

 nous proportions of the water molecules involved in such combina- 

 tions. The porous septum is the means of bringing out and render- 

 ing visible, both in electrical and ordinary osmose, this liquid move- 

 ment attending chemical combinations and decompositions. 



Although the nature and modus operandi of chemical action pro- 

 ducing osmose remains still very obscure, considerable light is thrown 

 upon it in the application of septa of animal membrane. Ox-bladder 

 was found to acquire greatly increased activity, and also to act with 

 much greater regularity when first divested of its outer muscular 

 coat. Cotton calico also impregnated with liquid albumen and 

 afterwards exposed to heat so as to coagulate that substance, was 

 sufficiently impervious, and formed an excellent septum, resembling 

 membrane in every respect. The osmometer was of the usual bulb- 

 form, but the membrane was supported by a plate of perforated zinc, 

 and the instrument provided with a tube of considerable diameter. 

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

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

 the tube, amounting to 100 millimeters, indicated that as much 

 water had permeated the membrane and entered the osmometer, as 

 would cover the whole surface of the membrane to a depth of one 

 millimeter, or one twenty-fifth part of an inch. Such millimeter 

 divisions of the tube become degrees of osmose, which are of the 

 same value in all instruments. 



Osmose in membrane presented many points of similarity to that 

 in earthenw*are. The membrane is constantly undergoing decompo- 

 sition and its osmotic action is exhaustible. Salts and other sub- 

 stances, also capable of determining a large osmose, are all chemi- 

 cally active substances, while the great mass of neutral organic sub- 

 stances and perfectly 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 unprece- 

 dented in such experiments. The rise of liquid in the tube with a 

 solution containing one-tenth of a per cent, carbonate of potash in 

 the osmometer, was 167 degrees, and with 1 per cent, of the same 

 salt 206 degrees, in five hours. With another membrane and 

 stronger solution, the rise was 863 millimeters, or upwards of 38 

 inches, in the same time, and as much water was therefore impelled 

 through the membrane as would cover its whole surface to a depth of 

 8' 6 millimeters or one-third of an inch. The chemical action must be 



