Germain Henri Hess

Germain Henri Hess
Germain Henri Hess
Born	7 August 1802 Geneva, Canton of Léman, Helvetic Republic
Died	13 December 1850 St. Petersburg, Russia
Nationality	Russian
Fields	Chemistry
Known for	Hess's law, Thermochemistry

Germain Henri Hess (Russian: Герман Иванович Гесс German Ivanovich Gess; 7 August 1802 – 30 November 1850) was a Swiss-born Russian chemist and doctor who formulated Hess's law, an early principle of thermochemistry.

Early days

Born in Geneva, Switzerland, his father was an artist and in 1805 moved the family to Russia to find work. In 1817, Hess moved to Tartu, Estonia, to attend high-school. In 1822, Hess studied medicine at the University of Tartu. He qualified as a physician in 1825.

Hess turned to chemistry after a meeting with Jöns Jakob Berzelius, the famous Swedish chemist, and went to Stockholm University to study under him. On his return to Russia, Hess joined an expedition to study the geology of the Urals before setting up a medical practice in Irkutsk.

Contributions to chemistry

In 1830, Hess took up chemistry full-time, researching and teaching, and later became a professor at the Saint Petersburg Technological Institute. His most famous paper, outlining his law on thermochemistry, was published there in 1840. His principle, a progenitor for the first law of thermodynamics, came to be called Hess's law. It states that in a series of chemical reactions, the total energy gained or lost depends only on the initial and final states, regardless of the number or path of the steps. This is also known as the law of constant heat summation.

Further studies and final days

Hess's other work concerned the investigation of minerals, including analysis of silver telluride (Ag₂Te), which was named Hessite in his honour. He also discovered that the oxidation of sugars yielded saccharic acid.

Hess was the author of a textbook on chemistry that was the standard Russian work for several decades. He died in St. Petersburg.