2G2 Dr. C. R. A. Wright on the Determination of 



known as " Faraday's law," or as " Faraday's first law of 

 electrolysis " (Part I. § 7), viz. that when a compound is 

 electrolysed the weight of substance decomposed is sensibly 

 proportionate to the quantity of electricity passing. Still, not 

 only Faraday himself, but also subsequent experimenters 

 have been led to doubt whether this law is rigorously true in 

 all cases, i. e. whether it is not possible for very weak currents 

 to pass through certain electrolytes without actually causing 

 electrolysis, or at least without causing an amount of elec- 

 trolysis precisely proportionate to the quantity of electricity 

 passing. In other words, it has been held that " conduction 

 without electrolysis " may occur in certain cases. On ex- 

 amining the experimental evidence in support of the doubt, 

 however, it does not seem to be at all proved in the cases in 

 which no electrolysis was apparent, even though a weak 

 current passed, that electrolysis did not actually take place, 

 the products being prevented from becoming visible owing 

 either to secondary chemical changes, or other circumstances. 

 More especially in the case of electrolysis of water is this 

 deficiency of proof noticeable ; for if the liquid electrolysed 

 were in contact with air before ordinary electrolysis, the 

 hydrogen evolved would necessarily be more or less com- 

 pletely suppressed by the oxidizing action of dissolved oxygen; 

 whilst even in the case of experiments with boiled fluids, or 

 fluids in vacuo, the impossibility of getting rid of the last 

 traces of oxygen dissolved in the fluid or occluded in the 

 electrodes &c. would still affect the quantity of free hydrogen 

 collected, as would also the power of the electrodes to occlude 

 within their material, or to condense upon their surface, the 

 hydrogen that would have appeared in the free state could 

 these actions of the electrodes have been completely elimi- 

 nated. Moreover it was shown long ago by Buff (Ann. der 

 Chem. unci Pharm. lxxxv. p. 1 , andxeiv. p. 15, 1853 and 1855) 



that currents in the ratio of ^, ^ , ^ — — , and 



WR + r' R + 2r' R + 4^ 



when passed through silver solutions deposited quantities 



of silver sensibly in the same ratio, even when the currents 



were so minute that the smallest of them only deposited 



0*129 gramme of silver in 100 hours, and hence deposited 



0*129 

 -— - — ttt — 7777 grammes per second, corresponding to a C.G.S. 



0-129 

 current of 9gAAnA ' , PQ = 0-0000308, or to 0*000308 

 360,000 x 0*01163 



weber (1 weber =0*1 C.G.S. current-unit), since 1 C.G.S. cur- 

 rent-unit deposits 0-011363 gramme of silver (Part I. § 9). 

 Similarly Buff found that currents capable of depositing 



