In previous papers' .2 the determination of bromine and tellurium were described. Other important impurities are phosphorus, chlorine and especially sulfur. These elements have already been determined in various matcrials3~4 and in seleniums-8. Chlorine is usually determined by y-spectrometry of the short-lived a&Cl after separation by volatilisation and precipitation as silver chloride. For large concentrations (> IO p.p.m.) non-destructive activation analysis of chlorine in selenium can be applied 7. When a double irradiation technique is used, sulfur and phosphorus can be determined through the isotope 33P or sulfur and chlorine through the isotope 3%. A separation of the matrix activities was obviously required: precipitation of selenium in the elementary state and sulfide precipitation of arsenic and germanium were found to be satisfactory.
SUCLEAR DATr, IRRADIATIOS
COSDITIONS
AKD INTERFERENCES
Reactor neutron irradiation of the elements phosphorus, sulfur and chlorine gives rise to the isotopes listed in Table -0 1". From this Table the various methods of dete:mination for these elements and the nuclear interferences are apparent. In the present work, chlorine was determined by counting 3*Cl while sulfur and phosphorus were determined through the ""P-activities from cadmium-covered and uncovered samples. These activities were corrected for the contribution of the exo-ergic 3sCl(n,a)3eP reaction and for the siP(n,y)3*P and a*S(n,p)3eP reactions. This method seemed preferable to the counting of the low-energy 36S, especially since this reaction is interfered with by the exo-ergic reaction aKl(n,p)a%.
Short irradiations favour the s%(n,p)a?P over the 3JS(n,y)3% reaction, as the half-lives are respectively 14.3 and 87 d. The counting of 3% was not considered, as the natural abundance and the activation cross-section of 3% ate too small to be applied in activation analysis.
When the double irradiation technique is applied with s*P counting, one can expect that the chlorine concentration should not exceed certain limits compared to the sulfur and phosphorus contents. The same consideration is true for the ratios of sulfur to phosphorus. OP DE BEECK AND HOSTESS calculated the amounts of sulfur and phosphorus which can be determined simultaneously, as a function of irradiation AfraZ. Claim. Ada, 43 (x968) I-II 'rmI.I! I NIICLI!AIt I'HW'liHTlliS 01' I'IIfJSl'lIOHlJS, SIJLI'IJH AND CIILOHINI! I<. I)Anfs AND F. AI)A~~s, i~adiochiru. Acta, in press.