Sulfanilic acid is an off-white crystalline solid which finds application in quantitative analysis of nitrate and nitrite ions. The solid acid exists as a zwitterion, and has an unusually high melting point. As the compound readily form diazo compounds, it is used to make dyes and sulpha drugs.This property is also used for the quantitative analysis of nitrate and nitrite ions by diazonium coupling reaction with N-(1-Naphthyl)ethylenediamine, resulting in an azo dye, and the concentration of nitrate or nitrite ions were deduced from the color intensity of the resulting red solution by colorimetry. The effects of sulfanilic acid, a major azo food dye metabolite, were studied in normal developing rat pups and pups treated with 6-hydroxydopamine (60HDA). Chronic daily intraperitoneal injection of sulfanilic acid during the first postnatal month elicited hyperactivity and impaired shock escape performance in vehicle pups.
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