A category of synthetic dyes made with a base material of coal-tar derivatives. Aniline is an organic compound derived from coal and oil, which was first isolated in the early 1820s. Its use as a base for dyes emerged in 1856, when William Henry Perkin identified mauveine, a substance that produces a purple colour, from coal-tar benzene. Following this discovery, several dyes using aniline as a base were synthesized, including indigo, reds, yellows and blacks.