Oily liquid compounds, colourless when pure. It was isolated in 1826 by distilling natural indigo with lime and discovered in coal tar in 1834. In 1841 it was found that it could also be obtained by heating caustic potash with indigo, and it then received its name, which is derived from nila (Sanskrit for indigo), an-nil (Arabic) and anilera (Portugese). In 1856 William Henry Perkin revolutionized the dyeing industry by using aniline to produce the first synthetic dye, ‘mauveine’. Obtained from coal tar derivates, it provides the chemical base of many modern synthetic dyes.