Spectrographic Determination of Trace Impurities in High-Purity Gold
A DC arc optical emission spectrographic method for the quantitative determination of 26 impurities in the range of 0.1 to 100 ppm is described. In this method, the gold sample is dissolved in aqua regia and the gold solution is then reduced by the addition of a weighed portion of high-purity graphite with the aid of hydrazine hydrate. The solution is evaporated to dryness and a 200-mg portion of the gold on graphite is pressed into a pellet which is burnt in a 20-A DC arc using a Stallwood Jet with an atmosphere of 70% argon—30% oxygen. The preparation of synthetic standards is described. Analytical lines used for the various elements, together with concentration ranges covered, are tabulated. Typical working curves for selected elements are shown. The overall precision for a total mean concentration of impurities at 280 ppm was found to be 5.1% expressed as coefficient of variation.
KeywordsHydrazine Hydrate Trace Impurity Chloroauric Acid Pellet Press Nickel Magnesium
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