Germain Henri Hess

Germain Henri Hess (7 August 1802 to 12 December 1850; in Russian, German Ivanovich Gess) was a Swiss-Russian chemist and medical doctor who formulated Hess' law, an early principle of thermochemistry. He was born in Geneva, moved with his family to the Russian Empire in 1805, studied medicine at the Imperial University of Dorpat and qualified as a physician in 1825. A visit to the Swedish chemist Jöns Jakob Berzelius turned him to chemistry for good, and from 1830 he researched and taught it full time, later as an adjunct professor of chemistry at the St. Petersburg Academy of Sciences. His 1840 paper stated that the total energy gained or lost in a series of chemical reactions depends only on the initial and final states, a special case of the conservation of energy that he formulated two years before Julius Robert von Mayer stated the more general principle. In 1842 he proposed the law of thermoneutrality, and his textbook Fundamentals of Pure Chemistry was the standard Russian undergraduate text until 1861. The mineral hessite is named after him, and he died in St. Petersburg at the age of 48.