ON THE SILVER VOLTAMETER. 597 



which have been noticed by ourselves and others. We hope at some future date to 

 enquire more closely into the nature of the impurities which affect so strongly the 

 weight of the deposit from the silver nitrate mother-liquors. 



M. Other Electrolytes. 



(1) Silver Acetate. Lord RAYLEIOH* found that the addition of a small quantity 

 of silver acetate to a solution greatly improved the texture of the deposit, but that 

 the mass of silver deposited per coulomb was considerably increased thereby. We 

 prepared a saturated solution of silver acetate and electrolysed in the usual manner ; 

 the deposit was of very fine texture, and the resulting electrochemical equivalent was 

 1 '12154 (31c) or 0'3 per cent, higher than the normal. There was evidence, however, 

 that the deposit was not silver alone, for on stripping a portion of it from the platinum 

 bowl a yellowish-white film was plainly visible on both silver and platinum where 

 they had been in contact, t 



(2) Silver Chlorate. Lord RAYLKIGH* also employed silver chlorate as an electro- 

 lyte, independent of the nitrate, and obtained very satisfactory results from it, and if 

 the mean value of the electrochemical equivalent is deduced from the chlorate 

 observations alone, it is higher than the value obtained with the nitrate solutions by 

 only 6 parts in 100,000. In our first attempt to use silver chlorate as an electrolyte 

 we used a 10 per cent, solution and obtained 1*11839 (49a) for the electrochemical 

 equivalent. It was apparent, however, that the electrolyte also contained silver 

 chloride, for a white precipitate had to be filtered from the original solution, and the 

 effect of silver chloride in solutions of silver chlorate is possibly the same as in 

 nitrate solutions. The chlorate was recrystallised to free from chloride and a 5 per 

 cent, solution used to minimise the effect of any remaining impurity. The resulting 

 deposit had a matt surface and its mass was 2 parts in 100,000 greater than that from 

 a 3 per cent, solution of the nitrate, but less by 1 part in 100,000 than that from a 15 

 per cent, solution (8 la, b, c). The electrochemical equivalent may therefore l>e taken 

 as I'll 827, and confirms Lord RAYLEIGH'S view that a solution of silver chlorate 

 gives the same mass per coulomb as one of silver nitrate. 



(3) Silver Perchlorate. CARHART, WILLARD and HENDERSON}: have suggested 

 the use of silver perchlorate as an electrolyte. They found the deposits from such a 

 solution to be striated and firmly attached to the bowl, but heavier than the deposits 

 from the nitrate by about 0'007 per cent. It appears, however, that silver chloride 

 may also have been present in the perchlorate, as instructions are given by them for 

 this to be filtered out. A small quantity of perchlorate was prepared for us by some 



* RAYF.EIQH and SIDOWICK, 'Phil. Trans.,' 175, p. 411, 1884. 



t VAN DIJK found n diminution in the mass of a silver deposit from an acetate solution when it wa 

 heated to a high temperature in an electric oven. 



I CARHART, WILLARD and HENDERSON, ' Amer. Electrochem. Soc.,' 1906. 



