1911 Encyclopædia Britannica/van't Hoff, Jacobus Hendricus

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4867961911 Encyclopædia Britannica, Volume 27 — van't Hoff, Jacobus Hendricus

VAN’T HOFF, JACOBUS HENDRICUS (1852–  ), Dutch chemist and physicist, was born in Rotterdam on the 30th of August 1852. He studied from 1869 to 1871 at the polytechnic at Delft, in 1871 at the university of Leiden, in 1872 with F. A. Kekulé at Bonn, in 1873 with C. A. Wurtz at Paris, and in 1874, when he took his doctor’s degree, with E. Mulder at Utrecht. In 1876 he became lecturer on physics at the veterinary school at Utrecht, and two years later he was chosen professor of chemistry, mineralogy and geology in Amsterdam University. In 1894 he declined an invitation to the chair of physics at Berlin University, but in 1896 he went to Berlin as professor to the Prussian Academy of Sciences, with a salary and a laboratory, but freedom to do whatever he liked; and at the same time he accepted an honorary professorship in the university so that he might lecture if he were so minded. On taking up these appointments he announced that, the application of mathematics to chemistry remaining his chief aim, he proposed to devote himself to the study of the formation of oceanic salt deposits, with special reference to the Stassfurt deposits. He may be regarded as the founder of the doctrine of stereoisomerism (q.v.), for he was the first, in 1874, to introduce a definite mechanical theory of valency, and to connect the optical activity exhibited by many carbon compounds with their chemical constitution. In respect of this doctrine of the “asymmetric carbon atom,” van’t Hoff’s name is generally linked with that of J. A. le Bel (born on the 21st of January 1847, at Pechelbronn, Lower Alsace), who, only two months later, independently enunciated the theory of asymmetric combinations with carbon; though it must be noted that J. Wislicenus, to whom van’t Hoff, in fact, acknowledged his indebtedness, had already suggested that in order to explain the constitution of certain organic bodies, the tridimensional arrangement of atoms in space must be taken into account. For this work van’t Hoff and Le Bel received the Davy medal jointly from the Royal Society in 1893. From 1874 to 1884 van't Hoff's attention was mainly given to the law of mass-action, and he established the theorem known by his name, which connects quantitative displacement of equilibrium with change of temperature. From 1885 to 1895 he was engaged on the theory of solutions, and developing the analogy between dilute solutions and gases he showed that the osmotic pressure of a solution has the same value as the pressure that solute would exert if it were contained as a gas in the same volume as is occupied by the solution. From 1885 he published the Zeitschrift für physikalische Chemie, in collaboration with Professor W. Ostwald of Leipzig.