Prior to irradiation tin is separated from a 1 g indium sample by iodide extraction followed by precipitation with Pb(OH)2. The amounts of tin introduced as contaminant before pre-irradiation treatment do not exceed 0.1 μg in most cases. After
irradiation in a thermal neutron flux of 5·1013 n·cm−2·sec−1 and suitable cooling the tin is extracted substoichiometrically with BPHA. The content of tin is determined on the basis
of the 158 keV photopeak of117mSn in the γ-spectrum. Other photopeaks appearing in the spectrum indicate the presence of various isotopes, it is then not
possible to determine tin on the basis of counting121Sn β-rays. The lower limit of determination is 0.2 ppm.