546 MR. F. E. SMITH, MR. T. MATHER, AND DR. T. M. LOWRY 



Page 



Effects of electrolysis on the concentration of various portions of the electrolyte 574 



The electrochemical equivalent of silver 579 



Comparison of results with those of other observers 579 



Conclusions 581 



PART II. 



Preparation of pure silver nitrate 581 



Tests of commercial silver nitrate 584 



Standard method of preparing silver nitrate solutions for electrolysis 585 



Effects produced by repeated electrolysis 586 



The question of anodic impurities 587 



Examination of the mother-liquors from recovered silver nitrate 589 



Striation of the deposit 590 



Influence of oxide, carbonate, and chloride 591 



Influence of sulphide 592 



Influence of nitrite and hyponitrite 593 



Influence of acids 594 



Effect of heating silver nitrate 596 



Electrolysis of a solution of silver acetate 597 



Electrolysis of a solution of silver chlorate 597 



Electrolysis of a solution of silver perchlorate 597 



Summary 598 



INTRODUCTION. 



IT has been known for several years that the measurement of electric quantity by 

 the electro-deposition of silver is liable to inaccuracies which appear to be dependent 

 on the condition of the anode, kathode, and electrolyte of the voltameter (or coulo- 

 meter) employed. In 1884 Lord RAYLEIGH* and Mrs. SIDGWICK found that a small 

 quantity of silver acetate added to a solution of silver nitrate or of silver chlorate 

 apparently increased the mass of silver deposited per ampere-second, and in 1895 

 RODGER and WATSONt showed that the silver voltameter was liable to give results 

 varying by as much as 1 part in 1000 when the same solution of silver nitrate was 

 repeatedly used. The latter effect was thought to be due to the formation of a 

 complex silver salt, and in 1899 RICHARDS, COLLINS, and HEIMROD| practically 

 confirmed this view. A new form of silver voltameter was suggested by the latter 

 observers, and this has been frequently used for observations of precision. In 1898 

 K AHLE made a very large number of measurements, using platinum and silver bowls 

 as kathodes and silver nitrate solutions, treated in various manners and from many 

 sources, as electrolytes. He found that the deposit of silver per colomb was greater 

 on a silver surface than on one of platinum ; that it increased with the continued use 



* RAYLEIGH and SIDGWICK, 'Phil. Trans.,' 175, p. 411, 1884. 



t RODGER and WATSON, 'Phil. Trans.,' A, 186, p. 631, 1895. 



J RICHARDS, COLLINS, and HEIMROD, 'Proc. Am. Ac.,' 35, p. 123, 1899. 



KAHLE, ' Zeitschr. Inst.,' 18, pp. 229-267, 1898. 



