“…Several methods have been described in which the material containing 35S is oxidized and the sulphate is precipitated as the barium or benzidine salt, the radioactivity of which is measured. Among the oxidation procedures which have been used are the Pirie (1932) method (Tarver & Schmidt, 1939;Boursnell, Francis & Wormall, 1946), the Carius method (Henriques, Kistiakowsky, Margnetti & Schneider, 1946), oxidation with concentrated nitric acid and hydrogen peroxide (Seligman & Fine, 1943), and oxidation with sodium carbonate and sodium peroxide (Dziewiatkowski, 1945).…”