Eilhardt Mitscherlich was a German chemist who discovered (1819) that compounds of similar composition tend to have the same crystal structure – the phenomenon known as isomorphism. This helped in the understanding of the relationship between the molecular composition and crystalline structures of compounds. In 1823, Mitscherlich discovered the monoclinic form of sulfur and in 1827 he discovered selenic acid. Mitscherlich named benzene and was the first to synthesize nitrobenzene (1832); he was also among the first to recognize catalysis (see catalyst.