A systematic chemical separation for thermal neutron activation analysis of seven noble metals in rock

A method for the systematic activation analysis of seven noble metals--ruthenium, silver, rhenium, osmium, iridium, platinum and gold--in rocks were developed and examined with radiotracers and irradiated rock samples. After the fusion of the irradiated rock sample with sodium hydroxide and sodium peroxide, 10% sodium sulfide solution is added and rhenium is extracted with pyridine-benzene mixture from 6N sodium hydroxide solution. From the hydroxide-sulfide precipitate fraction, ruthenium and osmium are distilled as tetroxides, silver is precipitated as chloride, gold is extracted with ethyl acetate, and iridium and platinum are extracted with diantipyrylmethane. Each fraction is purified and subjected to the gamma-ray spectrometry. Chemical yields for the elements are more than 60%. Determination limits are given for the seven elements.