MEASURING METHOD FOR PHOSPHORIC ACID-DERIVED PHOSPHATE CONCENTRATION IN WATER

摘要

PROBLEM TO BE SOLVED: To provide a measuring method by which the PO₄-P concentration even of water containing ionic silica can be measured with high accuracy by the molybdenum blue-ascorbic acid reducing technique.;SOLUTION: Regarding a sample colored by the molybdenum blue-ascorbic acid reducing technique of JIS K0101, an absorbance value of 880 nm light following the period of early abrupt coloring reaction of PO₄-P after reagent reaction is measured, followed by preparation of a polynomial regression formula line (y=Ax²+Bx+C) of the coloring period x and the light absorption plot y. From an intercept value C of this regression formula, a light absorption ratio T₀/T₁₅=D between T₀ after blank deduction and a light absorption ratio T₁₅ 15 minutes after blank deduction is set, and a PO₄-P concentration is obtained from a pre-obtained analytical curve by using the absorbance value after 15 minutes as the C/D value.;SELECTED DRAWING: Figure 1;COPYRIGHT: (C)2017,JPO&INPIT