Abstract
Studies on the conditions necessary to the determination of phosphate ions mainly in polluted river water were made. After extractable substances being removed beforehand with n-butylacetate in the acidic medium of 0.7N perchloric acid (with separating funnel), phosphate ions were transformed to molybdenum blue and colorimetric measurements were carried out at a wave length of 725mμ. Almost constant values are obtained even when the solution is kept standing for several hours for the coloration after the extraction, in the region of 0.41.0 N acidity, at 532°C. Any preparation of the calibration curves are unnecessary for at least 50 days within an error of about 5%. Any influences caused by the presence of less than 100mg of urea, less than 10 mg of di- and tri-carboxylic acids and less than 2 mg of lignin have not been found. No effect was observed in the coexistence of 100mg of mono-sugar, volatile mono-carboxylic acids, formaldehyde and phenols. When this method was employed to some of the samples such as highly polluted river water in Nagoya City, Kiso River and drainage from factories, it was determined at 94108% recovery rate by the additive test of 10μg of phosphate ions.
