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Prior to atomic absorption, cobalt in gold plating solutions was determined by polarography; copper, iron, and lead by optical emmission. With atomic absorption, both methods were consolidated with a significant decrease in analytical time. For the determination of cobalt in the range of 50 to 200 ppm the gold plating solutions are diluted, and the cobalt concentration is determined from a calibration curve constructed from Fisher Scientific Standards. To determine iron, lead, and copper in the range of 1 to 30 ppm the plating solutions are not diluted. In the course of the investigation it was found that iron and cobalt standards are unstable when stored in glass volumetric flasks. Polyethylene bottles have been found satisfactory for storing these standards. For the determination of cobalt and impurities in gold plates on copper and bronze the sample is dissolved in 1:3 nitric acid. Citrate is added to the nitric acid to complex the tin of the bronze. The solution then is filtered, and the insoluble gold plate is washed thoroughly with distilled water. Up to 25 mg of gold is dissolved in 3 ml of aqua regia, and the volume is adjusted to 25 ml with distilled water. The cobalt and impurities then are determined from curves constructed from standards which also contain 3 ml of aqua regia per 25 ml of solution.
gold plating solutions, plating solutions, gold plates, cobalt, copper, iron, lead, zinc, atomic absorption, standards, aqua regia, calibration, bronze, analyzing, tests
Kapetan, J. P.
Senior engineer, Western Electric Company, Inc., Chicago, Ill.