A Source of Error in the Colorimetric Estimation of Uranium

Abstract

FOR several years I have obtained consistent results with the hydrogen peroxide method¹ for the estimation of uranium, the intensity of the peruranate colour being measured with a Pulfrich photometer with filter S.43 (effective filter gravity, 434 mµ). In the hope of achieving greater accuracy and reproducibility, a modern type of spectrophotometer was recently substituted for the visual photometer, the colours being measured at 360 mµ (where the extinction for a given uranium content is nearly three times greater than at 434 mµ). It was found, however, that results were frequently low by as much as 30 per cent, although the same solutions gave the correct result when the absorption was measured with the Pulfrich photometer.