Phosphorus hemioxide

Phosphorus tetritoxide, P40) (Phosphorus hemioxide, P20). Phosphorous oxide, P404... 

J. J. Berzelius made phosphorous acid by treating phosphorous oxide with water —a reaction studied by T. E. Thorpe and A. E. H. Tutton, vide supra. B. D. Steele obtained it by the action of iodine on hypophosphorous acid (q.v.) in the presence of mineral acids and A. Besson, by heating the hemioxide with water in a sealed tube at 100° P20+024-3H20=2H3P0k. Phosphorous acid is also produced by the action of hot dil. nitric acid oh phosphorus the objection to this process, said J. Come, is the simultaneous production of phosphoric acid (q.v.), and this the more, the greater the cone, of the nitric acid. T. Salzer, and J. Philipp also reported that some hypophosphoric acid is produced at the same time. The early workers knew that the aq. soln. of phosphatic acid slowly decomposes, giving off phosphine, hence the faint smell like garlic. C. F. Sehonbein mentioned that freshly prepared phosphatic acid contains a trace of nitric acid as well as ozone. A. Tamm also observed that some phosphorous acid is formed when phosphated steel is dissolved in nitric acid. 

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