Gooch and Feiser — Silver by Electro-Deposition. 109 



Art. XIV. — The Estimation of Silver bij Electro-Deposition 

 from an A mmoniacal Solution of the Oxalate • by F. A. 

 Gooch and J. P. Feisetc. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — ccxvii.] 



In a recent paper from this laboratory an account is given 

 of tests upon the efficiency of a silver anode in the fixation 

 of chlorine derived from hydrochloric acid by electrolysis. It 

 was found in these tests that when the silver anode was made 

 by plating platinum gauze with silver in a solution of the 

 double cyanide of silver and potassium the silver deposit 

 invariably included some of the potassium salt. To secure 

 purity of the silver anode an ainmoniaeal solution of silver 

 oxalate was substituted for the double cyanide solution in 

 the plating process, for the reason that nothing of a non-volatile 

 nature can then be included in the deposit which after ignition 

 consists of pure silver. The present paper describes the 

 adaptation of this process to the quantitative estimation of 

 silver. 



The solutions of silver nitrate used in testing this process 

 were carefully standardized by precipitating silver chloride 

 from the hot solution by hydrochloric acid, cooling, digesting 

 over-night, and weighing the silver chloride upon asbestos after 

 heating gently without melting. Depositions were made upon 

 a rotating cathode of platinum — the ordinary crucible,* the 

 double disk of gauzef and a gauze cone set point downward 

 upon the axis of rotation. In the experiments of Table 1, 

 measured amounts of the silver nitrate solution (25 c ™ 3 or 50 cm3 ) 

 were drawn from a burette into a small beaker and treated 

 with ammonium oxalate to complete precipitation. The silver 

 oxalate was dissolved in a slight excess of ammonia, and this 

 solution, diluted to 100 cm3 , was electrolyzecl with a current of 

 0-25 — 15 amp. and 4—7 volts. The cathode with the deposited 

 silver was dried cautiously over a low flame and thereafter 

 ignited to incipient redness. The details of individual experi- 

 ments are given in the table. 



These results show plainly that the process of depositing 

 silver from the ammoniacal solution of the oxalate, precipitated 

 from the nitrate, is capable of yielding good analytical results. 

 Under the conditions of these experiments the electrolysis 

 should be continued from twenty-live to thirty minutes in 

 order to make sure that the deposition is complete. The 



* Gooch and Medway : this Journal, xv, 320 (1908). 



f Hildebrand : Jour. Amer. Chern. Soc, xxix, 450 (1907). 



