1. In contrast, the 'empirical formula' only expressed the stoichiometric composition of a substance. The distinction was originally Berzelius's, but the precise meaning of 'rational' formula changed with constitutional theories: Berzelius J., Jahresberichte, xiii (1834), 186
2. Crosland M. P., Historical studies in the language of chemistry (London, 1962), 323.
3. Organic Classification Before Kekulé