The Liesegang Phenomenon—an Historical Note

THE discovery of the phenomenon of periodic stratification in gels is attributed to Liesegang (Phot. Archiv, 1896, 221). Historical accounts of earlier experimental work on the formation of precipitates of sparingly soluble substances in gels are given by Wo. Ostwald (``Grundriss der Kolloidchemie,'' Dresden, 1909, 208) and by Bradford (Biochemical Journal, 29, 29, 1920). The latter author states (loc. cit., p. 29): ``The first observation of a series of layers (produced by periodic precipitation in gels) must be ascribed to Lupton (NATURE, 47, 13 (1892)).'' It may be observed that Ord published experiments before this date on the formation of calcium oxalate in isinglass gels. Details of these experiments are given in his book (``The influence of Colloids upon Crystalline Form and Cohesion,'' London, 1879), which, in the writer's opinion, has not received the attention it deserves. It appears from the passage quoted below (op. cit., p. 108) that Ord before 1879 (the actual date of the experiment is given in the text as March 12, 1869) had obtained stratified precipitates of calcium oxalate: