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Determination of purity of 24 carat (5N gold) using inductive coupled plasma-optical emission spectrometer

N.Raman, D.Sathiya Narayanan

Hallmarking centers determine the purity of 22 carat usually by cupellation (Fire assay) method as per IS 1417. In this method they are using 24 carat gold as an additive and the purity of 24 carat gold is also certified. The determination of purity of 24 carat gold involves the estimation of impurities present in it using Inductive Coupled Plasma-Optical Emission Spectrometer (ICP-OES) quantitatively. The general impurities are Ag, Cu, Pd, Fe, Pb,Mg,As, Bi, Sn, Cr, Ni,Mn, Ru, Ir, Pt, Os, Rh, Cd, Zn and Te as per STD ASTM B- 562. Upon adding the impurities present in gold, rest is purity by difference. Based upon the results, gold can be classified into different grades which are 99.500, 99.950, 99.990 and 99.995 % fineness. This analytical technique is most important for Hallmarking centers for ascertaining their 24 caratGold.