│Justus von Liebig│, was born at Darmstadt on May 12, 1803, and after graduating at Erlangen, where he worked on the fulminates, he repaired to Paris and entered the laboratory of Gay Lussac, with whom he continued his inquiries. Returning to Germany, he was appointed Professor of Chemistry at Giessen in 1826, and began those remarkable series of scientific contributions upon which the superstructure of organic chemistry largely rests. He investigated the _cyanates_, _cyanides_, _ferrocyanides_, _thiocyanates_, and their derivatives. In conjunction with Wöhler he discovered the group of the _benzoic compounds_ and created the _radical theory_. With Wöhler also he investigated _uric acid and its derivatives_. He discovered _hippuric acid_, _fulminuric acid_, _chloral_, _chloroform_, _aldehyde_, _thialdine_, _benzil_, and elucidated the _constitution of the organic acids_ and the _amides_. He greatly improved the methods of organic analysis, and was thereby enabled to determine the empirical formulæ of a number of carbon compounds of which the composition was imperfectly known. He practically laid the foundations of modern agricultural chemistry, and to his teaching is due the establishment of an important branch of technology—the manufacture of chemical fertilisers. He worked on physiological chemistry, especially on the elaboration of fat, on the nature of blood, bile, and on the juice of flesh. He studied the processes of fermentation, and of the decay of organised matter. He was a most prolific writer. The Royal Society’s Catalogue of Scientific Papers enumerates no fewer than 317 contributions from his pen. He was the founder of the _Annalen der Chemie_, which is now associated with his name, and of the _Jahresbericht_; he published an _Encyclopædia of Pure and Applied Chemistry_ and a _Handbook of Organic Chemistry_. His _Familiar Letters on Chemistry_ was translated into every modern language, and exercised a powerful influence in developing popular appreciation of the value and utility of science. Liebig left Giessen in 1852 to become Professor of Chemistry at the University of Munich and President of the Academy of Sciences. He died at Munich on April 18, 1874. With the name of Liebig that of Wöhler is indissolubly connected. Although the greater part of their work was not published in conjunction, what they did together exercised a profound influence on the development of chemical theory.