250 Prof. Daniell and Dr. Miller on the 



To ascertain whether the passage of the current from one 

 electrolyte to another was in any way concerned in preventing 

 the transfer of the base, we now resolved to employ sulphate 

 of copper in solution throughout the whole arrangement, and 

 having carefully ascertained the proportion of copper in solu- 

 tion, we placed 1500 grains of the liquid in each cell; metallic 

 copper was thrown down on the platinode, and on precipita- 

 ting the oxide from the liquid in the cell by potash, we found 

 exactly the same amount of copper (taking the united quanti- 

 ties obtained from the oxide precipitated, and from the metal 

 deposited) as before the experiment. An equivalent of sul- 

 phuric acid was set free at the zincode, but the quantity of the 

 copper solution in the cell continued the same as at the com- 

 mencement. Copper thus appeared to refuse to exchange 

 with itself in electrolysis. 



Sulphate of zinc afforded results exactly similar. 



[a. b.) That the diaphragm itself did not throw any ob- 

 struction in the way of such transfer we satisfied ourselves, by 

 varying its substance, from membranes to porous earthenware; 

 but this was put out of all doubt in the following manner. A 

 long siphon tube reversed was filled with a strong solution of 

 sulphate of copper, and two strips of copper were made the 

 electrodes of the battery ; the action proceeded very slowly, 

 but after a long time the liquid in the platinode limb of the 

 apparatus became sensibly lighter-coloured, while that in the 

 zincode became darker; the oxysulphion disengaged at the 

 latter point had dissolved the copper of the zincode, which, 

 however, had no power to pass to the platinode, to replace 

 the metal which had there been deposited. 



The preceding experiments bear closely upon an observa- 

 tion familiar to persons engaged in electrotyping on the large 

 scale, viz. that the solution around the platinode becomes im- 

 poverished, and at last nearly deprived of copper. 



As it appears to be thus established, that in the electrolysis 

 of complex electrolytes, the metals which are capable of de- 

 composing water at ordinary temperatures, or whose oxides 

 are largely soluble in water, are susceptible of transference in 

 the voltaic circuit from the zincode to the platinode, whilst 

 those which are not marked by this strong affinity for oxygen 

 remain stationary ; we were anxious to ascertain to which 

 class ammonium belongs. 



{a. c.) The aj)paratus was charged with a solution of mu- 

 riate of ammonia (NH4Cl)of known strength throughout; 

 35*5 cubic inches of hydrogen were collected from the plati- 

 node; the zincode liquid was yellow and smelt strongly of 

 chlorine. By careful neutralization with muriatic acid, it was 



