Abstract / scope
The method is applicable tp products with a content greater than 0,1 mg/kg. It is applied to a test portion as it is, and to another identical portion with a known quantity of arsenic added. The principle consists in 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.