Oxygen flask combustion tests

The simultaneous analysis of orthophosphate, glycerol phosphates, and inositol phosphates has been achieved by spectrophotometric analysis of the molybdovanadate complexes. Also, a sensitive and selective chemiluminescent molecular emission method for the estimation of phosphorus and sulphur is described, which is based on passing solutions into a cool, reducing, nitrogen-hydrogen diffusion flame. For organic compounds it was usually necessary to prepare test solutions by an oxygen-flask combustion technique. 

Prepare an analar solution of 12 g ammonium ferric sulphate in water and add 40 ml of analar nitric acid. Dilute to 100 ml. Prepare a solution containing 0.4 g of mercuric thiocyanate crystals in 100 ml of absolute alcohol. Mix 5 ml of the test solution from the oxygen flask combustion method (described above) with the ammonium ferric sulphate solution. Add 1.5 ml of mercuric thiocyanate solution. When chlorine is present an orange to red colour will develop in the test sample. If a semi-quantitative estimation of chlorine is required, set the solution aside for 10 min, then measure the optical density of this coloured solution against the blank solution at 460 nm in 20 mm cells. Typical calibration figures for the examination of plastic coatings such as PVC are as follows ... 

Ammonium limit test (31) Oxygen flask combustion method... 

Approximately 20 mg of polymer is combusted in an oxygen filled flask over dilute sodium hydroxide solution. Specific colorimetric tests for nitrogen, sulphur and phosphorus and the four halogens are applied to reveal the presence or absence of these elements. 

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