Recently a method was proposed by the author2 for the electrolytic determination of copper in tin-base alloys. In this method the sample was dissolved in hydrochloric and nitric acids, then phosphoric acid was added and the solution heated on the hot plate about a half hour to drive off the hydrochloric and nitric acids. The solutions were cooled, water added and the solutions boiled IO minutes to convert the pyrophosphoric acid to phosphoric acid. Nitric acid was then added and the copper deposited.
The method although an improvement over previously published methods for the determination of copper in tin-base alloys still leaves much to be desired. The 40 minutes heating required on the hot plate makes the method somewhat lengthy. During t-his heating care must be taken that the solution does not spatter and that salts clo not precipitate. If salts do form they will not readily dissolve2. A method is proposed in this paper which eliminates the above disadvantages.
In this method the sample is dissolved in a mixture of hydrofluoric and nitric acids, phosphoric acid and hydrogen peroxide arc added and the solution electrolyzed. No heating at all is required.
The purpose of the hydrofluoric and nitric acids in the method is to dissolve the sample rapidly. The purpose of the hydrogen peroxide is to oxidize the antimony and arsenicr, and destroy the nitrous acid. The phosphoric acid is necessary to prevent contamination of the deposit by antimony. When the phosphoric acid was omitted in the method serious contamination by antirnony was frequently obtained.
The method is amazingly fast. In fact, as far as the author knows, it is the most rapid method ever devised for the electrolytic determination of copper in any alloy, tin-base or otherwise. It takes just two minutes to prepare a sample for electrolysis. The electrolysis itself takes 15 minutes.
As in the previous method2 the electrolysis should not be prolonged beyond 20 minutes, otherwise some contamination of the deposit may occur. The method References p. S4r.