Illustration of Jean Dumas (1800-1884), French chemist. In 1830 Dumas challenged the views of Berzelius on chemical structure, proposing in its place his own 'type theory'. This showed that there existed families of atoms or groups in organic compounds that could be substituted for each other without seriously altering the properties of the compound. Later, he devised an analytical method for the determination of nitrogen in organic compounds, a major step in quantitative organic analysis. In 1848 he entered politics, retiring in 1870. Illustration published in 1879.