Germain Henri Hess (Russian: Герман Иванович Гесс, romanized: German Ivanovich Gess; 7 August 1802 – 12 December [O.S.

Hess graduated with honors from Dorpat University receiving a doctor of medicine degree with his dissertation entitled Something about Curative Waters, Especially Those in Russia.

[1] By application of Professors Osann and Engelhardt, Hess was sent to Sweden, to visit Swedish chemist Jöns Jakob Berzelius.

On his return to Russia, Hess joined an expedition to study the geology of the Urals before he was appointed a medical doctor at Irkutsk.

His experiments on various hydrates of sulfuric acid showed that the heat released when they formed was always the same, whether the reactions proceeded directly or through intermediates (1840).

Hess thus formulated a special case of the conservation of energy two years before Julius Robert von Mayer stated a more general principle, in 1842.

In 1842, Hess proposed the law of thermoneutrality, which states that no heat is evolved in the exchange reactions of neutral salts in aqueous solution.