The colorimetric determination of phosphorus in the presence of interfering substances

Abstract

RECENTLY, the present authors [Davies and Davies, 1931] described a method for the elementary analysis of phosphorus in pure organic compounds, by a modification of the Briggs-Bell-Doisy method. It was observed during the course of the above investigation that it was necessary to standardise the conditions exactly, in order to ensure accuracy. At the same time, one of us was working with Dr J. H. Quastel, in the Biochemical Laboratory of the Cardiff City Mental Hospital, upon the presence of phosphatases in brain tissue. It was then noted that sufficiently large quantities of potassium pyro- phosphate prevented the formation of the characteristic blue acid, due to the reduction of the yellow phosphomolybdic acid, resulting from the interaction between molybdic and orthophosphoric acids.