The Color Reactions of Lower Oxoacids of Phosphorus with Molybdate and their Application to Colorimetric Determinations of \overset4P–\overset3P–\overset4P– and (–\overset3P–)6–Acid

Abstract

Abstract The color reactions of twelve lower oxoacids of phosphorus, as well as of \overset5P– and \overset5P–O–\overset5P–acid with molybdate, have been described. Of these compounds, \overset2P–\overset4P, \overset4P–\overset3P–\overset4P– and (–\overset3P–)6–acid react with molybdate in the acid solution to produce a bluish-green color without any reducing agent. The bluish-green color caused by \overset2P–\overset4P–acid is not reproducible. Since the colors caused by \overset4P–\overset3P–\overset4P– and (–\overset3P–)6–acid are stable and since their intensities are proportional to their concentrations, one can detect and determine minute amounts of \overset4P–\overset3P–\overset4P– or (–\overset3P–)6–acid colorimetrically in the presence of the other oxoacids of phosphorus. When both \overset4P–\overset3P–\overset4P– and (–\overset3P–)6–acid are present in a given sample, one can determine each component by combining the method described above with the usual heteropoly blue method for the total phosphorus.