# The New International Encyclopædia/Liebig, Justus von

Edition of 1905. See also Justus von Liebig on Wikipedia; and the disclaimer.
LIEBIG, lē'bĭK, Justus von, Baron (1803-73). One of the greatest chemists of the nineteenth century. He was born at Darmstadt, Germany, the son of a dealer in dyestuffs. He early showed a strong predilection for natural science. At the age of fifteen he became apprenticed to an apothecary at Heppenheim, near Darmstadt. Soon after he entered the University of Bonn, then went to Erlangen, where he took his doctor's degree in 1822. In that year he published a paper on fulminating mercury, and in 1823 went to Paris, where, by further researches on the fulminates, he soon attracted the attention of Alexander von Humboldt. Humboldt introduced Liebig to Gay-Lussac, Thénard, and Dulong, and the young German chemist was hospitably received in the laboratory of Gay-Lussac. At the recommendation again of Humboldt, Liebig
was made professor of chemistry at the University of Giessen (1824), where he remained for more than a quarter of a century, attracting students from all parts of Germany and from foreign countries. In 1845 the Grand Duke of Hesse raised him to the rank of baron. In 1852 he became professor of chemistry at Munich, and in 1860 president of the Academy of Sciences and curator-general of the scientific collections of Bavaria. He remained in Munich until his death.
When Liebig began his career chemistry was in its infancy. Above all, organic analysis was in an extremely undeveloped state; so that a great deal of ingenuity was required in carrying out what are now very simple analytical determinations. At the time of Liebig's death chemistry, both pure and applied, had developed beyond all expectations; and Liebig had contributed more than any one of his contemporaries to its prodigious growth. Liebig established the first laboratory where students might receive a thorough practical training in chemistry, to supplement the instruction given in the lecture-room (see Laboratory), and in Liebig's own laboratory some of the most distinguished nineteenth-century chemists were trained. Another great service was his introduction of the well-known method of organic analysis. (See Chemistry, section Organic Chemistry.) The number of carbon compounds discovered and studied by Liebig himself was very great. He analyzed many important natural alkaloids; investigated the action of chlorine on alcohol and discovered chloral and chloroform; studied the products of oxidation of alcohol and discovered aldehyde; determined the basicity of many organic acids: investigated the chemical composition of urine and the derivatives of uric acid; analyzed the juice of flesh, etc. His theory of the constitution of alcohol, ether, and chloroethane, and the celebrated research carried out jointly with Wöhler (q.v. ) on the benzoyl compounds, gave a powerful impulse to the development of chemical theory. Among his contributions to chemical technology may be mentioned his method of making the cyanide of potassium, a compound extensively used in electroplating and in the manufacture of ferrocyanides. The discovery of aldehyde, mentioned above, has led to important improvements in the manufacture of mirrors and of vinegar.
The phenomena of animal and vegetable life formed one of Liebig's favorite branches of research, and he was the first to advance the theory that the activity of physical and chemical forces is the same in the organized as in the mineral world. He proved experimentally that animal heat is nothing but the energy liberated by the combustion in the organism mainly of fats and carbohydrates. Foods which serve as fuel and supply the heat of the body he termed respiratory foods. Nitrogenous substances, which — as he showed — serve to build up the tissues of the body, he termed plastic foods. He was also the first to prove that the transformation of inorganic into organic substances takes place exclusively in the organisms of plants, from which animals receive ready-formed the principal substances of their flesh and blood. Plants, on the other hand, receive their nourishment from the soil and the air, the former supplying them with the sulphates, sulphites, and phosphates of sodium, potassium, calcium, magnesium, and iron; while the atmospheric air supplies them with
carbonic acid, water, ammonia, and nitric acid. It thus became clear that, in order to maintain the fertility of the soil, the saline ingredients necessary for the growth of plants must from time to time be restored to it, either in isolated form or in the form of the sewage of towns, in which they are contained in considerable quantity. The importance to agriculture of the manufacture of saline fertilizers, which has thus originated in Liebig's researches, is inestimable, and Liebig may justly be considered as one of the founders of agricultural chemistry. See Chemistry, Agricultural.
Liebig's Chemistry in Its Application to Agriculture and Physiology appeared in Brunswick and in London in 1840. The second part of this epoch-making work was published under the title. The Natural Law of Husbandry (Brunswick, 1862; London, 1863). His Animal Chemistry, or Chemistry in Its Application to Physiology and Pathology, appeared in 1842 (Brunswick and London; 3d German ed., Brunswick, 1846). An English translation of his paper on foods appeared in London in 1847, under the title, Researches on the Chemistry of Food. The celebrated Handbook of Organic Analysis was published in Brunswick and in London in 1853. Liebig's publications further include: Handwörterbuch der Chemie, the compilation of which he began in conjunction with Poggendorff (9 vols., Brunswick, 1836-64, and a later edition); Handbuch der organischen Chemie (Heidelberg, 1839-43); Theorie und Praxis in der Landwirtschaft (Brunswick, 1856); Naturwissenschaftliche Briefe über die moderne Landwrtschaft (Leipzig, 1859), etc. The celebrated Chemische Briefe (Familiar Letters on Chemistry) first appeared in the Augsburger Allgemeine Zeitung (6th German ed. Leipzig, 1878); it has been translated into most European languages. The list of Liebig's scientific papers comprises more than 300 titles, each paper forming a valuable contribution to organic science. In his private life Liebig was kind and hospitable, noble in thought and generous in feeling. Numberless honors were bestowed upon him. Consult Hofmann, The Life-Work of Liebig in Experimental and Philosophic Chemistry (London, 1876).