Germain Henri Hess

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

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Early days

Born in Geneva, Switzerland, his father was an artist and in 1805 moved the family to Russia to find work. Beginning 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 came to be called Hess's Law, which holds 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 of 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.