Iodometric microdetermination of phosphorus in organophosphorus compounds containing nitrogen, sulfur and halogens

Abstract

A new general method is described for the iodometric microdetermination of phosphorus in organic compounds after combustion by the oxygen flask and absorption of the combustion products in bromine water. After removal of excess bromine by boiling and addition of acetone, the solution containing the interfering acids besides orthophosphoric acid is treated with iodide-iodate and the iodine liberated is treated with thiosulfate solution. This unrequired titer is equivalent to all interfering acids in addition to the first hydrogen ion of orthophosphoric acid. The dihydrogenphosphate ion left behind is then reacted with zinc and ammonium ions in the presence of excess solid KI and KIO 3. Acetone is added and the liberated iodine is titrated with 0.01 N thiosulfate. This second titer is equivalent to two hydrogen ions of orthophosphoric acid and is used to calculate the phosphorus content of the compound. This new method for elemental phosphorus microanalysis is considered, so far, to be most simple, rapid, accurate, and of wide application. Also described are methods for elimination of halogen, nitrogen and sulfur interferences in connection with other micromethods for phosphorus determination.