Previously published methods for the electrolytic determination of silver are not entirely satisfactory. The cyanide procedure gives good results for the determination of silver alone, but is not satisfactory as a separation of silver from copper unless a rather low current density is used6. Also, lead and bismuth will co-deposit with the silver. The use of a nitric acid medium for the deposition of silver is not satisfactory for the determinatiori of more than 0.05 to 0.x gram of silver on account of the difficulty of obtaining adherent deposits*lll. Copper and bismuth interfere in the deposition of silver from nitric acid solutions unless the cathode potential, or the voltage between the electrodes is controlled H.a. 7* 14. Also, there is some danger of silver depositing on the anode as the oxide'* Il. If a mercury coated platinum electrode is used instead of a regular platinum cathode, better results can be obtained in the deposition of large amounts of silver from nitric a&d solutions ll. However, the drying of the silver amalgam without any loss of the mercury is not an easy matterIS. The ammonium acetate -nitric acid procedure for silver gives good results for silver alone, but copper and bismuth interfere, unless the cathode potential or the voltage between the electrodes is controlledl8n Is. The use of an ammoniacal medium is satisfactory for determining silver alone but requires cathode potential control to separate silver from copper and other elements Ia. ls* lb. The use of an ammoniacal medium containing hydrogen peroxide is satisfactory for the determination of silver or the separation of silver from copper, but lead, nickel, and bismuth interferes.
In this paper a new electrolytic method for determining silver and separating silver from copper is proposed which has none of the disadvantages listed above. A nitric acid-sodium nitrite medium is used in this method. The deposits obtained are bright and adherent, even with large amounts of silver, and neither the amperage nor the voltage is critical. The presence of the nitrite prevents the formation of silver oxide at the anode. Bismuth, lead, nickel, cobalt, cadmium, zinc, iron, chromium, manganese, and aluminum do not interfere. After the determination of the silver, the electrolyte can be boiled down to destroy the nitrite and the copper deposited.
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