Isoperthiocyanic acid (3-amino-5-thione-l, 2, 4-dithiazole) as a new reagent for the selective detection of nitrite ion

Abstract

A new, simple, and selective test is described for the detection of nitrite ion with isoperthiocyanic acid (I) as the reagent. The test is based on the reaction of a 5% solution ofI with the nitrite ion solution, a deep orange precipitate being formed. Conversely, the test can be used in the identification ofI itself. Presumably, the coloured product is 3-hydroxy-5-thione-1, 2, 4-dithiazole, formed by the action of nitrous acid (producedin situ by the action of sulphuric acid and nitrite) on the 3-amino group ofI. The limit of detection is 300μg of NO2− in a drop (0.05 ml). Most anions (including IO3−) do not interfere. Only I−, thiourea, and hydrogen peroxide interfere; S2O32− interferes only when present in large amounts.