Germain Henri Hess studied heat changes accompanying chemical reactions. Hess's law expresses the additivity of compatible reaction enthalpies: reversing a reaction reverses the sign, and combining reaction equations combines their enthalpy changes. This makes it possible to obtain an otherwise inaccessible heat change from an enthalpy cycle.[ref]
Royal Society of Chemistry biographical notice: edu.rsc.org/resources/on-this-day-aug-08--henri-hess-was-born/10808.article
Portrait of Germain Henri Hess
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