LIEBIG, JUSTUS VON, BARON (1803-1873), German chemist, was born at Darmstadt in May, 1803. His father, a dry salter and dealer in colours, used sometimes to make experiments in the hope of improving his processes and thus the son early acquired familiarity with practical chemistry. For the theoretical side he read all the text-books which he could find. At the age of fifteen he entered the shop of an apothecary at Appenheim, near Darmstadt ; but he soon found how great is the difference be tween practical pharmacy and scientific chemistry. He next entered the university of Bonn, but migrated to Erlangen with the professor of chemistry, K. W. G. Kastner (1783-1857). He then went to Paris, where, by the help of L. J. Thenard he gained admis sion to the private laboratory of H. F. Gaultier de Claubry (1792— 1873), professor of chemistry at the Ecole de Pharmacie, Paris, and soon afterwards, by the influence of A. von Humboldt, to that of Gay-Lussac. There he concluded, in 1824, his investiga tions on the composition of the fulminates. On Humboldt's ad vice he determined to become a teacher of chemistry, and after overcoming many difficulties he was appointed extraordinary pro fessor of chemistry at Giessen in 1824, becoming ordinary pro fessor two years later. His most important work was accom plished at Giessen. He persuaded the Darmstadt government to provide a chemical laboratory in which the students might obtain a proper practical training. This laboratory, unique of its kind at the time, in conjunction with Liebig's unrivalled gifts as a teacher, soon rendered Giessen the most famous chemical school in the world. In it were trained many accomplished chemists and it gave a great impetus to the progress of chemical education throughout Germany. Liebig remained at Giessen for twenty-eight years, until, in 1852, he became professor of chemistry at Munich University. He died at Munich on April Io, 1873.
Work on Pure Chemistry includes improvements in tech nique of organic analysis, his plan for determining the natural alkaloids and for ascertaining the molecular weights of organic bases by means of their chloroplatinates, his process for determin ing the quantity of urea in a solution, and his invention of the simple form of condenser known in every laboratory. His con
tributions to inorganic chemistry were numerous, including inves tigations on the compounds of antimony, aluminium, silicon, etc., on the separation of nickel and cobalt, and on the analysis of mineral waters, but they are outweighed in importance by his work on organic substances. In this domain his first research was on the fulminates of mercury and silver, and his study of these bodies led him to the discovery of the isomerism of cyanic and fulminic acids. Further work on cyanogen and connected substances yielded a great number of interesting derivatives, and he described an improved method for the manufacture of potas sium cyanide.
In 1832 he published, jointly with \\Tallier, one of the most famous papers in the history of chemistry, that on the oil of bitter almonds (benzaldehyde), wherein it was shown that the radicle benzoyl might be regarded as forming an unchanging con stituent of a long series of compounds. Berzelius hailed this dis covert' as marking the dawn of a new era in organic chemistry. A continuation of their work on bitter almond oil by Liebig and \Willer resulted in the elucidation of the mode of forma tion of that substance and in the discovery of the ferment emul sin as well as the recognition of the first glucoside, amygdalin; another and not less important and far-reaching inquiry in which they collaborated was that on uric acid, published in 1837. About 1832 he began his investigations into the constitution of ether and alcohol and their derivatives. These on the one hand resulted in the enunciation of his ethyl theory, by the light of which he looked upon those substances as compounds of the radicle ethyl ; on the other they yielded chloroform, chloral and aldehyde, as well as other compounds, and also the method of forming mirrors by depositing silver from a slightly ammoniacal solution by acetalde hyde. In 1837, with Dumas, he published a note on the constitu tion of organic acids, and in the following year an elaborate paper on the same subject appeared under his name alone; by this work T. Graham's doctrine of polybasicity was extended to the organic acids. Liebig also did much to further the hydrogen the ory of acids.