Perrin, radiation theory

Perrin J 1922 On the radiation theory of chemical action Trans. Faraday Soc. 17 546-72... 

Perrin s theory was flawed both in his failure to clearly express the radiation hypothesis in quantum terms and in his concrete examples of monomolecular reactions. Thomas Martin Lowry, recently appointed to a new chair of physical chemistry at Cambridge University, argued that Perrin s choices of chemical examples were unfortunate. 

In addition, Perrin tended to interest himself in individual atomic events rather than in the molecule as a complex entity. The radiation theory of chemical activation attempted a mathematical representation in simple and general formulas, based on axiomatic principles. Perrin s work in radiation bears more resemblance to his reformulation of thermodynamics in the early 1900s than to his experimental work on x-rays and cathode rays in the 1890s or on colloids and Brownian motion in the early 1900s. What binds all his work together is interest in single events or the individual corpuscle. 106... 

Still, Perrin s commitment ran deep, and when he edited Job s lecture, "Mecanismes chimiques," for publication in a collection of essays after his death in 1928, Perrin added references to his own revisions of the radiation theory published in 1926 and 1928. He also appended a reprint of his 1928 article from the Comptes Rendus of the Academy of Sciences. See Formes chimiques, 154, n. 2 156, n. 2 and 160164. 

Perrin s argument that the very nature of a unimolecular reaction demands independence of collisions, and therefore dependence on radiation, is adequately met both by the theory of Lindemann and by that of Christiansen and Kramers. Both these theories have the essential element in common that the distribution of energy among the molecules is not appreciably disturbed by the chemical transformation of the activated molecules thus the rate of reaction is proportional simply to the number of activated molecules and therefore to the total number of molecules, sinc in statistical equilibrium the activated molecules are a constant fraction of the whole. Thus the radiation theory is not necessary to explain the existence of reactions which are unimolecular over a wide range of pressures. 

Radiation screen theory. Midgley 188 adopted Perrin s theory, that radiations from the initial flame activate and accelerate reaction by splitting the hydrocarbons into a more reactive condition, in explaining knocking and assumed that antiknocks acted as screens for absorbing the radiation and controlling the velocity of flame movement. Experimental proof in support of this theory has not been obtained and its merit will be difficult to demonstrate. The theory is not adequate, however, to explain the action of knock inducers. 

In the early twenties, several scientists puzzled over how a reacting molecule in an unimolecular reaction could acquire sufficient internal energy to react. Jean Perrin proposed in 1919 that energy was provided by radiation from the walls of the reaction vessel. Frederick Lindemann, the later Lord Cherwell, strongly objected against this Radiation Theory of Chemical Action and presented an alternative view in 1921, which is still regarded as essentially correct. It explains a remarkable feature of unimolecular reactions The rate of a unimolecular reaction is first order in the reactant at normal pressure, but may become second order at low pressure. 

Perhaps best known of Perrin s work is his spirited defense of kinetic theory and physical atomism entitled Les atomes (1913), in which he made use of his own work on Brownian motion, in combination with studies of cathode rays and x-rays, ionization, radioactivity, radiation, and quantum theory.72 About the time of the 1911 Solvay physics conference, Perrin shifted from Brownian motion to work on thin films, fluorescence, and photochemistry, partly to test the early quantum theory and especially to study individual atom-based fluctuations. 

Attempts to find a satisfactory microscopic theory for unimolecular reactions in the gas phase started in 1919, when Perrin [1] suggested that infrared radiation must be absorbed by the reactants in the activation step of such reactions. He argued that since the phenomenological rate law... 

In this period there was a great attention about the molecularity of mechanisms and of particularly interest was a debate about unimolecular reactions. The debate was that about the so called Radiative Theory (King Laidler, 1984), proposed mainly by Jean Baptiste Perrin (1870-1942), around 1917. Perrin propwsed that unimolecular processes was activated only by blackbody radiation. The hypwthesis, fallacious, continued for nearly ten years involving many and important figures as Einstein for example. Even being wrong Radiative Theory represents an interesting case study and boosted the research on different activation causes other than thermal collisions. 

A revival of interest in this area began around 1913 with the radiation hypothesis , due to M. Trautz, Jean Perrin and WilUam Lewis. The particular challenge they tackled would probably have escaped notice of the scientific community, except for the fact that Perrin and Lewis were two highly respected scientists. Their developments required a strong mathematical preparation. Lewis was the first chemist to develop a theory of chemical... 

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