THE APPLICATION OF DIOCTYL SULPHIDE IN THE ANALYSIS OF NOBLE METAL ELEMENTS——Ⅱ.DETERMINATION OF TRACE GOLD IN GEOLOGICAL SAMPLE BY NAA

A method for determining trace gold in geological sample by using dioctylsulphide pre-extraction-NAA has been developed. 5 grams of sample are weighedand decomposed by means of mixed acid (HF-HNO_3-HClO_4). The residue is dis-solved in aqua regia. Gold is extracted by dioctyl sulphide-chloform solution.Aliquot of organic extract is transferred quantitively to filter paper and heated todryness under infra-red lamp. After pile neutron activation, the samples are allow-ed to cool for 24 hours and ~(198)Au is counted by means of Ge (Li) γ-spectro-metry. The content of gold in the sample is dctermined by the comparator method.The chemical yield of ~(198)Au through the complete procedure is 92%. The precisionof the mcthod is ±10%.