354- Professor Daniell on the 



the diaphragm which separated the two solutions. The cir- 

 cuit conducted very readily, and the action was very energetic. 

 Hydrogen was given off at the platinode in a solution of 

 potassa, and oxygen at the zincode in the sulphate of copper. 

 A small quantity of gas was also seen to rise from the surface 

 of the diaphragm. In about ten minutes the lower surface 

 of the membrane was found beautifully coated with metallic 

 copper, interspersed with oxide of copper of a black colour, 

 and hydrated oxide of copper of a light blue. 



" The explanation of these phsenomena is obvious. In the 

 experimental cell we have two electrolytes separated by a 

 membrane, through both of which the current must pass to 

 complete its circuit. The sulphate of copper is resolved into 

 its compound anion, sulphuric acid + oxygen (oxysulphion), 

 and its simple cathion copper: the oxygen of the former escapes 

 at the zincode, but the copper on its passage to the platinode 

 is stopped at the surface of the second electrolyte, which for 

 the present we may regard as water improved in its conduct- 

 ing power by potassa. The metal here finds nothing by 

 combining with which it can complete its course, but being 

 forced to stop, yields up its charge to the hydrogen of the 

 second electrolyte, which passes on to the platinode, and is 

 evolved. 



" The corresponding oxygen stops also at the diaphragm, 

 giving up its charge to the anion of the sulphate of copper. 

 The copper and oxygen thus meeting at the intermediate 

 point, partly enter into combination, and form the black oxide; 

 but from the rapidity of the action, there is not time for the 

 whole to combine, and a portion of the copper remains in the 

 metallic state, and a portion of the gaseous oxygen escapes. 

 The precipitation of blue hydrated oxide doubtless arose from 

 the mixing of a small portion of the two solutions." 



Nitrate of silver, nitrate of lead, proto-sulphate of iron, sul- 

 phate of palladium, and proto-nitrate of mercury, were simi- 

 larly treated, and afforded analogous results, somewhat modi- 

 fied by the nature of the metallic base. ' Sulphate of magnesia 

 was subjected to the same process, in hopes of finding mag- 

 nesium, but magnesia alone was deposited. 



The theory of ammonium, as proposed by Berzelius, and the 

 hypothesis of Davy developing the general analogy of all salts, 

 whether derived from oxyacids or hydracids, may by this evi- 

 dence, especially when taken in conjunction with the recent 

 researches on the constitution of organic bodies, be considered 

 as almost experimentally demonstrated*. 



The bisalts yield results which at first sight do not accord 



* See Ad itional Note at the end of the present Number among the 

 Miscellaneous Notices. 



