ISO 2590:1973

Applicable to determining the quantities contained either in all the test solution or in the aliquot portion of between 1 g and 20 g that is taken for the determination. The principle bases on the reduction of the arsenic by zinc in a hydrochloric acid medium 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.