Determination of silicon in metals by thermal neutron activation

A simple and rapid method of estimating the amount of rubidium in coconut palm leaves by neutron-activation analysis is described. The irradiation unit consisting of a standard and two samples of palm leaves in sealed silica vials was irradiated at a neutron flux of 0.2 to 10x1013n cm-2sec-1 for 1-7 days. The irradiated sample is dissolved in aqua-regia. The solution is made 11N with respect to HCl, treated with 1 g of HAP and centrifuged. The supernatant is concentrated, treated with stannic chloride in 6N HCl and chilled at 3 deg C. The precipitate of rubidium chlorostannate is separated, transferred to a weighed counting tube, dried at 100 deg C, weighed and counted on a single channel pulse-height analyser coupled to a well-type 3.8 cm x 3.8 cm NaI(Tl) detector. The method is found suitable for the estimation of stable Rb used as a tracer in root distribution studies. The average of five determinations is 5.15 μg, which varies between 5.07 μg and 5.26 μg at a 95% confidence limit. (T.G.)