René Marcelin (12 June 1885 – 24 September 1914) was a French physical chemist, who died in World War I at a young age. He was a pupil of

Jean Baptiste Perrin Jean Baptiste Perrin (; 30 September 1870 – 17 April 1942) was a French atomic physicist who, in his studies of the Brownian motion of minute particles suspended in liquids (sedimentation equilibrium), verified Albert Einstein's explanation o ...

at the Faculty of Sciences in

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

and performed theoretical studies in the field of

chemical kinetics Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a ...

Work

René Marcelin developed the first theoretical treatment of the rate of

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

s that goes beyond a simple empirical description. He showed that the expression of the

rate constant In chemical kinetics, a reaction rate constant or reaction rate coefficient () is a proportionality constant which quantifies the rate and direction of a chemical reaction by relating it with the concentration of reactants. For a reaction between ...

given by the

Arrhenius equation In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 188 ...

had to be composed of two terms. In addition to the

activation energy In the Arrhenius model of reaction rates, activation energy is the minimum amount of energy that must be available to reactants for a chemical reaction to occur. The activation energy (''E''a) of a reaction is measured in kilojoules per mole (k ...

term, he considered that there had to be an activation entropy term. In 1910, Rene Marcelin introduced the concept of standard Gibbs energy of activation. In 1912, he treated the progress of a chemical reaction as a motion of a point in

phase space The phase space of a physical system is the set of all possible physical states of the system when described by a given parameterization. Each possible state corresponds uniquely to a point in the phase space. For mechanical systems, the p ...

. Using Gibbs' statistical-mechanical methods, he obtained an expression similar to the one which he had obtained earlier from thermodynamic consideration. In 1913, René Marcelin was also the first to use the term

potential energy surface A potential energy surface (PES) or energy landscape describes the energy of a Physical system, system, especially a collection of atoms, in terms of certain Parameter, parameters, normally the positions of the atoms. The Surface (mathematics), ...

. He theorized that the progress of a chemical reaction could be described as a point in a potential energy surface with coordinates in atomic momenta and distances. In his PhD thesis, which he defended in 1914, he developed a general theory on absolute reaction rates, in which he used concepts of both thermodynamic and kinetic origin, describing the activation dependent phenomena as the movement of representative points in space. His 1915 publication, published shortly after his death, describes a chemical reaction between N atomic species in a 2N-dimensional phase space, using statistical mechanics to formally obtain the pre-exponential factor before the exponential term containing the Gibbs free energy of activation. The foundations of his theoretical treatment were correct, but René Marcelin was not able to evaluate the remaining integrals in his expressions, as the solution of these equations was not achievable at that time. René Marcellin also developed the dividing surface approach to study rates of transport in Hamiltonian systems. These results were published after his death by his brother André in 1918.Keith J. Laidler, The World of Physical Chemistry. Oxford University Press, Oxford, 1993.

References

{{DEFAULTSORT:Marcelin, Rene Chemical kinetics 1885 births 1914 deaths French military personnel killed in World War I University of Paris alumni