Bidrag til et thermochemisk System. - [THE FIRST ENUNCIATION OF THE THERMOCHEMICAL AFFINITY PRINCIPLE]

(Copenhagen, 1852). 4to. Bound in fine recent marbled boards with leather-title on frontcover with gilt lettering. pp. (115)-165 (as issued in: Det Kongelige Danske Videnskabernes Selskabs Skrifter volume 5:III, 1852).

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First edition of Thomsen's main contribution in the field of Thermochemistry, undoubtly the main contribution by a Dane in chemistry in the 19th Century. The paper from 1852 is famous as it is the first statement of a new thermochemical nomenclatura, and the paper contains the first enunciation of the thermochemical affinity principle, which states that chemical affinity, or the attraction between substances, can be measured by the heat evolved when bodies combine. His fundamental thought was that the evolution of heat accompanying a chemical reaction (which he calls 'varmetoning', equivalent to enthalpy change) is an exact expression of the chemical affinity of the reaction.