Principle of Berthelot

Melting-point.—It did not escape Berthelot that his principle is not applicable to processes like the melting of crystalline substances. As a matter of fact, the heat of fusion is always positive, i.e. heat is always evolved in the transition from the liquid to the crystalline state. At low temperatures the process does proceed as required by the principle of Berthelot, i.e. in the direction in which heat is... 

Similar considerations were advanced by M. Berthelot (1805), and this so-called Principle of Maximum Work found its way in some form or other, into all chemical treatises. The following, among other, objections were later brought against it ... 

From Pierre Duhem, Traite elementaire de mecanique chimique fondee sur la thermodynamique, 2 vols. (Paris Hermann, 1897), I vi. The doctoral thesis, Lepotentiel thermodynamique et ses application a la mecanique chimique et a la theorie des phenomenes electriques (1886), was rejected, partly because of its criticism of the "principle of maximum work" developed by the influential Collee de France chemist Marcellin Berthelot. 

So the idea, the concept of enzyme action as a general principle in biochemical reactions was that of Berthelot in the 1850 s, as to the priority. The experimental verification however was Buchner s work, and he earned the merit for it. 

Analogous considerations lead to the conclusion that the reverse must be true at high temperatures. Both conclusions are most completely verified by experience. Indeed a law was stated by Thomsen, and especially by Berthelot —by the latter under the name of the principle of maximum work — that all chemical reactions which take place of their own accord are accompanied by evolution of heat. 

In 1854 J. Thomsen stated the following proposition, which Berthelot has called the Principle of Maximum Work ... 

In their endeavours to measure chemical forces by means of thermal quantities, Berthelot and Thomsen were undoubtedly guided by the law of the conservation of energy, but the principle of maximum work is by no means a necessary consequence of this law. The first law merely states that the (positive or negative) heat evolved in a chemical reaction is equal to the change in energy of the transformed substances. Under what conditions the reaction will take place or fail to take place is a question which it is beyond the scope of the first law of thermodynamics to decide. The direction in which an energy change will proceed can only be determined with the aid of the second law of thermodynamics. 

This equation demonstrates the falseness of Berthelot s principle (p. 128), which states that the affinity and the heat of reaction are equal to one another. We see further that A and Qp approach one another as the temperature is diminished to the absolute dA... 

The hydrogen-oxygen or Knall-gas cell, as it is often called, offers a very striking lllustiation of the inapplicability of the Berthelot principle of considering heat as the measure of affinity Thus m the case of the cell,... 

This served as the guiding principle of extended researches by Berthelot (1827-1907) and by Thomsen (1826-1909), to whom the greater part of our data on thermochemistry is due. However, it can be seen from equation (38) that the available work (not including mechanical work which is usually very small) can only be equal to the heat of reaction (a) at absolute zero or (b) if the Gibbs free energy does not change with the temperature. This latter statement also means, of course, that the electromotive force of a cell in which the reaction takes place does not change with the temperature, i.e.,... 

Here, in contrast with the examples of pages 139 and 143, the value which has to be added to the first term on the right-hand side is, as we have already indicated, not inconsiderable, and is, moreover, of the opposite sign thus, according to our formula, we must be encountering a totally different behaviour, namely, a complete breakdown of Berthelot s Principle this has been fully confirmed quantitatively. When... 

Berthelot, Marcellin (or Marcelin) Pierre Eugene (1827-1907) French chemist and politician noted for the Thomsen-Berthelot principle of thermochemistry he synthesized many organic compounds from inorganic substances and disproved the theory of vitalism. 

Berthelot was aware that some reactions occur spontaneously with absorption of heat, but he supposed that here foreign energies were involved. He later restricted the principle of maximum work (although heat was really used instead of work ) to reactions between solids, when it is approximately correct, and defined chemical heat, to which the principle applies, as that transformable into work, which is really free energy (see below). 

Van t Hoff then deals with chemical equilibrium on the basis of the law of mass action, and the change of equilibrium constant with temperature, introducing the case of condensed systems in the absence of vapour and a transition point (point de transition). Physical equilibria are special cases of chemical equilibria. Graphical methods with vapour pressure curves (e.g. for the allotropic forms of sulphur) are introduced. The principle of mobile equilibrium is explained for homogeneous and heterogeneous equilibria, and the Thomsen-Berthelot principle criticised (see pp. 614, 620). The last chapter, on affinity ,gives the definition The work of affinity (A) is equal to the heat produced in the transformation (q), divided by the absolute temperature of the transition point (P) and multiplied by the difference between this and the given temperature (P) ... 

Berthelot, M.-P. Chimie organique fondee sur la synthese, 1860 Mendeleev, D. L origine du petrole. Revue Scientifique, 1877,2e Sen, Vni, 409 16. Mendeleev, D. The Principles of Chemistry, vol. 1. Second English edition translated from the sixth Russian edition. Collier New York, 1902 552 pp. 

Berthelot Marcelin (1827-1907) Fr. chem., enunciated the principle of maximum work, known for his sharp criticism ( Essai de mecanique chimique fondee sur la thermochimie 1879)... 

Few measurements of important parameters are as simple to make as the partition coefficient of a solute between water and octanol. The principles of the shake-flask measurements remain the same as in the Berthelot and Jungfleisch reports of 1872 and the further analysis by Nemst. Yet the interplay of solvation forces in both the water and octanol phases are so involved and complex that current molecular mechanics and quantum chemical calculations can dispel very little of the empiricism that now dominates logP estimation. It is difficult to predict how soon ab initio calculations will give us dependable information regarding the conformation, the tautomeric form, and the electron distribution of complex solutes, not just as they exist in a vacuum or crystal, but also as they exist in the aqueous phase as well as the water-saturated octanol phase. At present the quantum chemical methods that look the most promising for the complex solutes seem to fail when applied to the simplest hydrophobic organic structures of all the aliphatic hydrocarbons. 

In spite of the fact that the general statement of this principle has been shown to be false from all standpoints, it must be admitted that its enunciation was quite in harmony with the spirit of the times the great physicists Lord Kelvin (1851) and Helmholtz (1847) had previously formulated an identical principle in connection with galvanic cells. Thomsen and Berthelot went wrong, not in tlieir enunciation of the so-called theorem as a working hypothesis, but rather in their... 

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