Thomas H. Norton
1895 Journal of the American Chemical Society  
These determinations furnish, we believe, satisfactory proof that the method which has been described, secures a practically complete precipitation of the phosphorus, even when the amount present is only 0 . 0 2 per cent., and also that the ratio of phosphorus to molybdenum in the solution is constant and independent of the amount of phosphorus present ; also that the ratio is not affected by the presence of silicon or arsenic in the solution. T h e cast iron used contains 0.84percent. of
more » ... 84percent. of silicon. As regards arsenic, we have applied Marsh's test for arsenic to the yellow precipitate obtained froni two grams of steel No. 2, and obtained only a very faint arsenic mirror, much fainter than that obtained under the sanie conditions, from 0 . 0 2 mgm. of arsenious oxide. If we suppose the arsenic to have been present in a compound analogous to the phosphorus conipound, t!ie molybdenum associated with it would correspond to only 0.0003 per cent. of phosphorus. The determinations with the cast iron also furnish evidence that the conversion of phosphorus into phosphoric acid is as coniplete by solution in nitric acid and oxidation with potassium permanganate as by solution in aqua regia and evaporation with nitric acid. The volumetric deterininationswith the cast iron are niore accordant than the gravimetric. In view of the great difficulties known to exist in the way of securing pure magnesium pyrophosphate, we believe the volumetric determination will usually be found to be more accurate.
doi:10.1021/ja02157a009 fatcat:mkzxjbqchvetnhutu3lvzoamzq