152 Royal Society. 



sisted of the porous cylinder employed in voltaic batteries, about 

 5 inches in depth, surmounted by an open glass tube 06 inch in dia- 

 meter, attached to the mouth of the cylinder by means of a cap of 

 gutta percha. In conducting an experiment the cylinder was filled 

 with any saline solution to the base of the glass tube, and immediately 

 placed in a large jar of distilled water ; and as the fluid within the 

 instrument rose in the tube, during the experiment, water was added 

 to the jar so as to prevent inequality of hydrostatic pressure. The 

 rise (or fall) of liquid in the tube was highly uniform, as observed 

 from hour to hour, and the experiment was generally terminated in 

 five hours. From experiments made on solutions of every variety of 

 soluble substance, it appeared that the rise or osmose is quite insig- 

 nificant with neutral organic substances in general, such as sugar, 

 alcohol, urea, tannin, &c. ; so also with neutral salts of the earths 

 and ordinary metals, and with chlorides of sodium and potassium, 

 nitrates of potash and soda and chloride of mercury. A more sen- 

 sible but still very moderate osmose is exhibited by hydrochloric, 

 nitric, acetic, sulphurous, citric and tartaric acids. These are sur- 

 passed by the stronger mineral acids, such as sulphuric and phos- 

 phoric acid and sulphate of potash, which are again exceeded by 

 salts of potash and soda possessing either a decided acid or alkaline 

 reaction, such as binoxalate of potash, phosphate of soda and car- 

 bonates of potash and soda. The highly osmotic substances were 

 also found to act with most advantage in small proportions, pro- 

 ducing in general the largest osmose in the proportion of one-quarter 

 per cent, of salt dissolved. Osmose is eminently the phsenomenon 

 of weak solutions. The same substances are likewise always che- 

 mically active bodies, and possess affinities which enable them to 

 act upon the material of the earthenware septum. Lime and alu- 

 mina were accordingly always found in solution after osmose, and 

 the corrosion of the septum appeared to be a necessary condition of 

 the flow. Septa of other materials, such as pure carbonate of lime, 

 gypsum, compressed charcoal and tanned sole-leather, although not 

 deficient in porosity, gave no osmose, apparently because they are 

 not acted upon chemically by the saline solutions. Capillarity alone 

 was manifestly insufficient to produce the liquid movement, while 

 the vis motrix appeared to be chemical action. 



The electrical endosmose of Porrett, which has lately been defined 

 with great clearness by Wiedemann, was believed to indicate the 

 possession of a peculiar chemical constitution by water, while liquid, 

 or at least the capacity to assume that constitution when polarized 

 and acting chemically upon other substances. A large but variable 

 number of atoms of water are associated together to form a liquid 

 molecule of water, of which an individual atom of oxygen stands 

 apart forming a negative or chlorous radical, while the whole remain- 

 ing atoms together are constituted into a positive or basylous radical, 

 . which last will contain an unbalanced equivalent of hydrogen giving 

 I the molecule bnpicity, as in the great proportion of organic radicals. 

 i Now it is this voiun»inous basylous radical that travels in the elec- 

 -j trical decomposition of pure water, and resolves itself into hydrogen 



