RECENT PROGRESS IN PHYSICS. 381 



served that fluids are transferred without any decomposition from one 

 electrode to the other. -^ — (Ann. of Philos., Jul., 1816; Fogg. Ann. XII., 

 618.) He divided a glass vessel by a diaphragm of bladder into two 

 cells, filled them with water, and suspended in each a platinum plate 

 connected with the poles of a battery of 80 pairs. In this way nearly 

 the whole of the fluid was transferred to the negative cell. This eflect 

 did not take place when the conducting power of the water was 

 improved by the addition of sulphuric acid. Daniell used distilled 

 water in his decomposing cell. On connecting it with a battery of 30 

 cells, a few bubbles only appeared at the electrodes, but none was 

 disengaged, (in this case again the insertion of a tangent compass 

 would have been very desirable;) but after 40 minutes the fluid at the 

 negative pole was \ inch higher than at the positive. When a little 

 freshly precipitated alumina was difi'used in the water at the positive 

 pole, a portion of this finely divided solid matter evidently passed 

 with the water to the negative pole. When the cell was filled with 

 a mixture of 8 jiarts of water and one of sulphuric acid, no change of 

 level took place. But nevertheless this phenomenon does not depend 

 upon the conducting power, for it frequently appears with saline solu- 

 tions, which conduct well, even in a higher degree than with pure 

 water. 



When the cell with the porous diaphragm contained sulphate of 

 soda, the fluid in the negative cell rose H inch, while nine cubic 

 inches of oxygen were liberated there; with phosphate of soda the 

 difference in height was 2 inches. Nitrate of potasa produced this 

 transfer in a much less degree. 



In order to ascertain whether in this process of transfer the entire 

 fluid was carried over or only the salt, or the water, Daniell examined 

 the specific gravity before and after the exj)eriment without finding 

 any perceptible difference. 



Whatever may be the immediate cause of this phenomenon, it appears 

 to have some analogy with the translation of good conducting sub- 

 stances, which in the formation of the luminous Voltaic arc serve as 

 a continuous connexion between the two poles. Daniell believes that 

 this process has no relation to endosmosis. 



§ 174. Eleclrolysis of polyhasic salts. — Daniell in connexion with Miller 

 extended his researches on electrolysis to still more complicated cases. 

 (Philos. Transact., f. 1844, pt. I; Pogg. Ann. LXIV, 18.) Of these 

 we shall now consider more in detail the electrolysis of the different 

 modifications of the phospliates. But to make these interesting phe- 

 nomena intelligible to those not familiar with the constitution of the 

 phosphates, I shall briefly explain the most important part of the 

 theory, referring i'or an exceedingly clear exposition of the subject to 

 Otto & Graham's Lehrhuch der Chemie, 2d edition, second volume, page 

 380. 



The common phosphoric acid PO^ forms, with soda, three different 

 salts, viz: 



3N,0,P0, 1.) 



2N; OHO, PO5 2.) 



N, 02HO, Po, 3.) 



the second of which is the common officinal phosphate of soda; it was 



