Sulphanilic acid (tech. & pure)

As the compound readily form diazo compounds, it is used to make dyes and sulpha drugs.^[2] 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.