August Wilhelm von Hofmann

August Wilhelm Hofmann was born at Giessen, Grand Duchy of Hesse, on 8 April 1818. He was the son of Johann Philipp Hofmann, privy councillor and provincial architect to the court at Darmstadt. As a young man, he travelled widely with his father. August Wilhelm matriculated at the University of Giessen in 1836. He obtained his PhD there in 1841. In 1843, after his father's death, he became one of Liebig's assistants. He had eleven children. ==Career==

Royal College of Chemistry in London Trading Card, 1929 As president of the Royal Society in London, Albert, Prince Consort to Queen Victoria, was determined to foster scientific advancement in Britain. In 1845, he proposed to start a school of practical chemistry in London, under the style of the Royal College of Chemistry. Liebig was approached for advice, and recommended Hofmann to the directorship of the new institution. Hofmann and the Prince met when Prince Albert, on a visit to his alma mater at Bonn, found his old rooms now occupied by Hofmann and his chemical apparatus. With the support of Prince Albert, and funding from a variety of private sources, the institution opened in 1845 with Hofmann as its first director. The financial position of the new institution was somewhat precarious. In 1853, the Royal College of Chemistry became part of the governmental Department of Science and Art, under the new School of Mines, putting it in a position to receive governmental funding on a somewhat more secure basis. Berlin University In 1864 Hofmann was offered a chair of chemistry at the University of Bonn, and another at the University of Berlin. While taking his time to decide which offer to accept, Hofmann designed laboratory buildings for both universities, which were both subsequently built. In 1865 he succeeded Eilhard Mitscherlich at the University of Berlin as professor of chemistry and director of the chemical laboratory. He held the position until his death in 1892. Following his return to Germany Hofmann was the principal founder of the German Chemical Society (Deutsche Chemische Gesellschaft zu Berlin) (1867) and served 14 terms as its president. ==Contributions==

Hofmann's work covered a wide range of organic chemistry. Organic synthesis Hofmann was a major contributor to the development of techniques for organic synthesis, which originated at Liebig's laboratory in Giessen. Hofmann and John Blyth were the first to use the term "synthesis", in their paper "On Styrole, and Some of the Products of Its Decomposition," predating Kolbe's use of the term by some months. What Blyth and Hofmann called "synthesis" enabled them to make inferences about the constitution of styrole. A subsequent paper, Muspratt and Hofmann's "On Toluidine", described some of the first "synthetical experiments" (synthetische Versuche) in the field of organic chemistry. While the ultimate goal of such experiments was to artificially produce naturally occurring substances, such a goal was not practically attainable at the time. The immediate purpose of the technique was the application of known reactions to a variety of materials to discover what products could be formed. Understanding a substance's method of formation was an important step in placing it within a developing taxonomy of substances. This technique became the basis of Hofmann's research program. He used organic synthesis as a method of investigation, to increase chemical understanding of reaction products and the processes by which they were formed. Coal tar and anilines Hofmann's first research investigations, carried out in Liebig's laboratory at Giessen, was an examination of the organic bases of coal tar. Hofmann successfully isolated Kyanol and Leucol, bases previously reported by Friedlieb Ferdinand Runge, and showed that Kyanol was almost entirely aniline, previously shown to be a decomposition product of the plant dye indigo. In his first publication (1843) he demonstrated that a variety of substances which had been identified in contemporary chemical literature as obtainable from coal tar naphtha and its derivatives were all a single nitrogenous base, aniline. These included Kyanol, Carl Julius Fritzsche's Anilin, Otto Unverdorben's Krystallin, and Nikolai Zinin's Benzidam. In 1856, Hofmann's student William Henry Perkin was attempting to synthesize quinine at the Royal College of Chemistry in London, when he discovered the first aniline dye, mauveine. The discovery led to the creation of a wide range of artificially created colourful textile dyes, revolutionising the fashion world. Hofmann's researches on rosaniline, which he first prepared in 1858, were the beginning of a series of investigations on colouring matter. In 1863, Hofmann showed that aniline blue is a triphenyl derivative of rosaniline and discovered that different alkyl groups could be introduced into the rosaniline molecule to produce dyes of various purple or violet colours, which became known as 'Hofmann's violets'. After his return to Germany, Hofmann continued to experiment with dyestuffs, finally creating quinoline red in 1887. Hofmann's original colour scheme (carbon = black, hydrogen = white, nitrogen = blue, oxygen = red, chlorine = green, and sulphur = yellow) has evolved into the CPK colour scheme and is in use even today. After 1874, when van't Hoff and Le Bel independently suggested organic molecules can be three-dimensional, molecular models began to assume their modern appearance. Hofmann voltameter The Hofmann voltameter is an apparatus for electrolyzing water, invented by August Wilhelm von Hofmann in 1866. It consists of three joined upright cylinders, usually glass. The inner cylinder is open at the top to allow addition of water and an ionic compound to improve conductivity, such as a small amount of sulphuric acid. A platinum electrode is placed inside the bottom of each of the two side cylinders, connected to the positive and negative terminals of a source of electricity. When current is run through Hofmann's Voltameter, gaseous oxygen forms at the anode and gaseous hydrogen at the cathode. Each gas displaces water and collects at the top of the two outer tubes. ==Publications==

Hofmann was multilingual and published extensively, particularly about his work on coal tar and its derivatives. In 1865 Hofmann published An Introduction to Modern Chemistry, summarising type theory and emerging ideas about chemical structure. Type theory modelled four inorganic molecules, hydrogen, hydrogen chloride, water, and ammonia, and used them as a basis for systematising and categorising both organic and inorganic compounds by exploring the substitution of one or more atoms of hydrogen for an equivalent atom or group. Hofmann himself had focused on researching ammonia, but discussed all four models in his book. In it, he also first introduced the term valence, under its longer variant quantivalence, to describe the combining capacity of an atom. His textbook strongly influenced introductory textbooks in both Europe and the United States. In addition to his scientific works, Hofmann wrote biographical notices and essays on the history of chemistry, including a study of Liebig. == Awards and honours ==

He was elected a fellow of the Royal Society in 1851. He was awarded the society's Royal Medal in 1854 and their Copley Medal in 1875 "for his numerous contributions to the science of chemistry, and especially for his researches on the derivatives of ammonia". On his 70th birthday, in 1888, he was ennobled, enabling him to add the prefix "von" before his last name. ==Later life==

Hofmann died in 1892 and was buried in Berlin's Dorotheenstadt Cemetery. == See also ==