Electrolysis of Secondary Compounds. 355 



with the preceding deductions; a strong solution, for example, 

 of pure crystallized bisulphate of potassa was made, and its 

 neutralizing power carefully ascertained by the alkalimeter. 

 Evaporation and ignition with carbonate of ammonia gave the 

 quantity of neutral sulphate yielded by a certain measure of the 

 solution. An equal measure was then placed in each arm of 

 the double diaphragm cell, and the current passed through 

 till 70*8 cubic inches of mixed gas were collected ; half the so- 

 lutions from the zincode and platinode were then separately 

 neutralized, and half evaporated and ignited in the vapour of 

 carbonate of ammonia. 



It was then found that the zincode had gained 18 grains ; 

 the platinode lost ]9 of free acid: of potassa the zincode 

 had lost 9 '9 grains, and the platinode gained an equal quan- 

 tity : thus, though the solution conducted very well, not more 

 than one-fifth of an equivalent of the potassa was transferred to 

 the platinode, as compared with the hydrogen evolved, while 

 half an equivalent of acid was transferred to the zincode when 

 where a whole equivalent of oxygen was evolved. Mr. Daniell 

 remarks upon this experiment, 



" I think we cannot hesitate to admit that, in this case, the 

 current divided itself between two electrolytes, and that a 

 part was conducted by the neutral sulphate of potassa, and a 

 larger part by the sulphuric acid and water. It is a well- 

 known fact that the voltaic current will divide itself between 

 two or more metallic conductors in inverse proportion to the 

 resistance which each may offer to its course; and that it does 

 not in such cases choose alone the path of least resistance. 

 I am not aware that such a division of a current between two 

 electrolytes in the same solution has ever before been pointed 

 out, but analogy would lead me to expect it." These consi- 

 derations enable us to explain some apparent anomalies in the 

 electrolysis of diluted sulphuric acid and alkaline solutions. 



When diluted sulphuric acid was placed in the double 

 diaphragm cell, and the current transmitted, some of the acid 

 passed to the zincode ; but from numberless experiments it 

 appeared that this quantity scarcely ever exceeded the propor- 

 tion of one-fourth of an equivalent as compared with the hy- 

 drogen evolved. Mr. Daniell thought possibly this might be 

 owing to the acid being mechanically carried back to the 

 platinode, as in all cases there is a mechanical convection of 

 the liquid from the zincode to the platinode, and this is the 

 greater in proportion to the inferiority of its conducting 

 power. If, however, this deficiency of acid were owing to a 

 mechanical re-transfer, mechanical means, such as increasing 

 the number of diaphragms, would stop it; the proportion, 



2A2 



