The concepts and theories of modern physics / By J.B. Stallo.

  • John Stallo
Date:
1900
Catalogue details

Licence: In copyright

Credit: The concepts and theories of modern physics / By J.B. Stallo. Source: Wellcome Collection.

    351/376 (page 301)
    The next noteworthy result of thermo-chemical re- search was the discovery that the nature of the chemi- cal reactions between different substances depends upon the relations between the specific energies of the re- agents as determined by the quantities of heat evolved or involved in the progress of these reactions. It was found that there are certain elements—oxygen and hydrogen, for example—which combine readily, and, under proper conditions, spontaneously, the combina- tion ({IS Berthelot expresses it) taking place directly, without the aid of extrinsic energy, and being at- tended with the evolution of light, or heat, or both. Such combinations are termed by M. Berthelot, exo- thertnic. They result in the formation of compounds, which can not be resolved again into their original elements without a restoration of the amount of en- ergy lost in the combimition. On the other hand, there are cases of endothermic combination in which conversely the composition of the elements is attended with an absorption, and the decomposition of the result- ing compound with a liberation, of heat. The com- bination of carbon and sulphur, for instance, is endo- thermic. Carbonic disulphide is formed by passing vaporous sulphur over red-hot charcoal; the union of carbon and sulphur is possible only on condition of the continuous supply, during the progress of the union, of heat, which is given out again when the disulphide is resolved into its elements. The facts here referred to are explained, by the modern chemist, on the theory that chemical affinity is transformed heat, both heat and affinity being forms of energy; that in the cases of ex- othermic combination the sum of the speciiic energies of the component elements exceeds the specific energy of the compound formed, while in endothermic com-