Gibbs, Josiah Willard (1839-1903) was a US scientist who laid the foundation of modern chemical thermodynamics. He devised the phase rule and formulated Gibbs' adsorption isotherm. Gibbs was born on 11 February 1839 in New Haven, Connecticut, into an academic family. His father was Professor of Sacred Literature at the Divinity School of Yale University, and Gibbs excelled at classics at school. He attended Yale in 1854, winning prizes for Latin and mathematics before graduating in 1858 at the age of only 19. During the next five years he continued his studies by specializing in engineering and in 1863 gained the first Yale PhD in this subject for a thesis on the design of gears. He then accepted teaching posts at Yale, first in Latin and then in natural philosophy. In 1866 he patented a railway braking system. Also in 1866 Gibbs went abroad for three years to attend lectures (mainly in physics) in Paris, Berlin and Heidelberg. In 1871, two years after his return to the United States, he was appointed Professor of Mathematical Physics at Yale, a post he retained until his death despite offers from other academic institutions. He never married but lived with his sister and her family. He died in New Haven on 28 April 1903. Gibbs did not publish his first papers until 1873, which were preliminaries to his 300-page series On the Equilibrium of Heterogeneous Substances (1876-1878). In it he formulated the phase rule, which may be stated as: f = n + 2 - r, where f is the number of degrees of freedom, n the number of chemical components, and r the number of phases - solid, liquid or gas; degrees of freedom are quantities such as temperature and pressure which may be altered without changing the number of phases. Gibbs did not explore the chemical applications of the phase rule, later done by others who came to realize its importance. In the same work he also described his concept of free energy, which can be used as a measure of the feasibility of a given chemical reaction. It is defined in terms of the enthalpy, or heat content, and entropy, a measure of the disorder of a chemical system. From this Gibbs developed the notion of chemical potential, which is a measure of how the free energy of a particular phase depends on changes in composition (expressed mathematically as the differential coefficient of the free energy with respect to the number of moles of the chemical). The fourth fundamental contribution in this extensive work was a thermodynamic analysis which showed that changes in the concentration of a component of a solution in contact with a surface occur if there is an alteration in the surface tension - the Gibbs' adsorption isotherm. All of these very technical discoveries now form part of the armoury of the physical chemist and thermodynamicist, together with their extension to electrochemistry and the subsequent developments of other scientists. But for many years Gibbs' work was unknown outside the United States, until it was translated into German by Friedrich Ostwald in 1891 and into French by Henri Le Châtelier in 1899. During his teaching studies Gibbs adapted the work of the mathematicians William Hamilton (1805-1865) and Hermann Grassman (1809-1877) into a vector analysis which was both simple to use and easily applicable to physics, particularly electricity and magnetism. It was left to one of Gibb's students, E.B. Wilson, to write a textbook on the subject, which was largely responsible for the popularization of vector analysis. Also during the 1880s Gibbs worked on the electromagnetic theory of light. From an entirely theoretical viewpoint and making very few assumptions he accounted correctly for most of the properties of light using only an electrical theory. In his last major work, Elementary Principles of Statistical Mechanics , Gibbs turned his attention to heat and showed how many thermodynamic laws could be interpreted in terms of the results of the movements of enormous numbers of bodies such as molecules. His ensemble method equated the behaviour of a large number of systems at once to that of a single system over a period of time. Author not available, Gibbs, Josiah Willard (1839-1903). , The Hutchinson Dictionary of Scientific Biography, 01-01-1998. |