:><H MR. F. E. SMITH, MR. T. MATHKK, AND DR. T. M. LOWRY 



manufacturing chemists, but it was far from pure, and our results are not therefore 

 comparable with those of CARHART. The chloride was filtered out, and when a 

 5 per cent, solution was used, the value T11860 (Bid) milligrammes per coulomb 

 resulted; subsequently we used a 10 per cent, solution and obtained I'll 840 (836). 

 We infer that pure perchlorate of silver will give the same value as pure nitrate, but 

 it is much more difficult to prepare. 



(4) Acting on a suggestion of Mr. W. C. D. WHETHAM, we prepared an electrolyte 

 by dissolving silver nitrate in pyridine. Considerable heat was evolved during 

 dissolution, but the liquid was quite clear. On electrolysis the deposited silver was 

 of a brownish-red tint, but when washed with very hot water the intensity of the 

 colour was considerably reduced. It was apparent, however, that the mass was not 

 pure silver, and the result (1'11890) (676) is not of very great interest. 



(5) Fused Silver Nitrate. MERRILL* was successful in obtaining coherent deposits 

 from fused silver nitrate, and compared them with deposits obtained from solutions of 

 the same salt. He concluded that the masses were identical. We have on several 

 occasions deposited about 7 grammes of silver on platinum bowls and obtained very 

 coherent deposits, but errors introduced in the manipulation have so far prevented 

 us from making a satisfactory comparison with deposits obtained in the usual way. 



Summary. 



1. It is possible to prepare again and again samples of silver nitrate which give in 

 the voltameters described in Part I. of this communication values for the electro- 

 chemical equivalent which do not vary by more than 3 parts in 100,000 on either 

 side of the mean figure. 



2. A standard method of purification is described. Commercial samples are usually 

 pure, but cannot be absolutely relied on. 



3. High values are obtained for the electrochemical equivalent if the solution 

 contains oxide, carbonate, chloride, nitrite or hyponitrite. Low values are caused by 

 the presence of acid. 



4. Impurities which increase the mass of the deposit per coulomb are usually 

 substances which are insoluble in water, but soluble in silver nitrate solutions ; they 

 are therefore precipitated from the impoverished solution at the kathode. 



5. Silver chlorate and silver perchlorate appear to give normal deposits, but are 

 more troublesome in use and have no advantage over the nitrate. 



6. There may be slight changes in the electrolyte due to its interaction with filter 

 paper, but the mass of the deposit is not seriously affected thereby in our size of 

 voltameter in the course of one electrolysis at ordinary temperatures. It is inadvisable, 

 however, in measurements of precision, to use an electrolyte more than once. 



* MERRILL, 'Phys. Kev.,' 10, p. 170, 1900. 



