The concentration of silver nitrate is not critical. When the quantity of silver nitrate was varied from 7 to 30 mmoles, the determination of 0.65 mmole of phosphorus pentoxide (93.1 mg.) was reproducible within 0.1 mg. A value of 15 mmoles of silver nitrate was selected for routine use.Results (Table 11) show that from about 2 to 200 mg. of phosphorus pentoxide can be determined within 0.1 mg.The possible interference of common substances was studied. Table I11 shows that potassium, ammonium, nitrate, and acetate ions give no significant change in results. Both sodium and sulfate ions cause slightly high results when present in large amounts. Silicate is the only substance studied that is a serious interference. This method would not be satisfactory if arsenate, chromate, tungstate, vanadate, etc., were present. Multivalent cations would also interfere. A prior removal by some other technique, such as ion exchange, is necessary before this method can be used.Chloride, bromide, iodide, cyanide, thiocyanate, and oxalate, which form insoluble silver compounds, can be removed by a preliminary volatilization with nitric acid. The solution containing nitric acid must be heated almost to dryness to remove these anions completely. The resulting salts must be hydrolyzed for about 4 hours in warm Determination of Radioantimony by Extract io n i n to D i i s 0 b u ty I ca r b i no I A simple liquid-liquid extraction procedure has been developed for determining radioantimony in mixed fission products. Antimony(V) is extracted from a 7M HCI-6M t i 3 P 0 4