Determination of phosphorus in silicate rocks by activation analysis

A neutron activation method for the determination of phosphorus from ammonium phosphomolibdate precipitate is applied to silicate rocks. Ammonium phosphate is added as carrier to the irradiated rock powder and the phosphorus is recovered as ammonium phosphomolibdate, which is precipitated several times in the presence of appropriate holdback carriers to ensure its radiochemical purity and then finally dissolved and reprecipitated as AgTlPO4 for weighing and counting. The samples were irradiated for 3 1/2 days in a thermal flux of 2.1010 n.s-1.cm-2 and the β-activities were measured by an end-window Geiger-Mueller counter. The results for rock standards granite G-1 and diabase W-1 are given. (K.A.)