ISO 3359:1975

Phosphoric acid for industrial use — Determination of arsenic content — Silver diethyldithiocarbamate photometric method

Applicable to products having As contents of more than 0.1 mg/kg. Relates to the method of analysis according to ISO 2590. Reduction of the As by zinc in a hydrochloric acid solution with the formation of arsine. Absorption of the arsine in a solution of silver diethyldithiocarbamate in pyridine. Photometric measurement of the purplish-red colour produced by the colloidally dispersed silver at the maximum of the absorption curve at a wavelength of about 540 nm. Determination of the quantity of As by means of the calibration curve.