酸素ボンブ法によるリンの比色定量

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Recoveries of phosphorus by the "oxygen bomb" method were examined by using filter paper impregnated with standard phosphate solution and by molybdovanadophosphoric acid spectrophotometry. To attain the highest recoveries of phosphorus (95.7% on an average), it was found crucial that the combustion product was transferred to a conical beaker wholly and was digested with perchloric and nitric acids. The reason would be that the phosphate was polymerized by the heat of combustion and reverted to the original orthophosphate by the acid digestion. Phosphorus in a surface active agent was determined by both the oxygen bomb method and the wet ashing procedure. The result obtained by the former method was 95.5% of that by the latter procedure. This percentage is almost the same as the recoveries by the oxygen bomb method. Trace phosphorus in an ethylene-propylene copolymer was determined by both the oxygen bomb method and the dry ashing procedure. About 65% of the result by the former method was obtained by the latter procedure. The "oxygen bomb" is a useful tool to decompose rapidly the samples which are hardly treated with the wet ashing procedure or in which phosphorus is not recovered entirely by the dry ashing procedure. Procedure for polymers : Wrap about 1 g of sample in a sheet of rice paper, fasten the paper with cotton thread, put the sample on the platinum capsule, and tie up the remaining parts of the thread through the coil of platinum wire {See Bunseki Kagaku, 21, 285 (1972)}. Impregnate the paper with a few drops of n-butanol, insert the head into the cylinder, and close the screw cap. After filling up oxygen gas in the bomb up to the pressure of 25 kg/cm2, ignite the sample by turning on electricity (10 V, AC). Keep the bomb in the water bath for 20 minutes before release, release the residual gas, and open the bomb. Wash the interior surfaces of the bomb and the capsule with water by using a policeman, and collect the bomb washings to a 200 ml conical beaker. Add 4 ml of nitric acid (60%) and 4 ml of perchloric acid (60%), digest the content in a ventilating hood until the fume of perchloric acid is evolved. Add about 30 ml of water and heat again to remove the nitric acid thoroughly. Cool, transfer to a 50 ml volumetric flask, and dilute to volume with water. Pipet a 10 ml aliquot of the above solution into a 25 ml volumetric flask. Add 5 ml of 5.6N perchloric acid, 3 ml of 0.02 M ammonium metavanadate in 0.4 N perchloric acid solution, and 5 ml of 0.2 M ammonium molybdate. Dilute to volume and allow to stand for 30 minutes. Transfer the solution to a 1 cm cell and measure the transmittance at 400 nm against water.
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酸素ボンブ法によるリンの比色定量

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