Germain Henri Ivanovitch Hess was a chemist born in Geneva, Switzerland, on August 7, 1802. He studied one of the most important principles of thermochemistry and developed Hess's Law.

He studied medicine, chemistry and geology at Tartu University from 1822 until 1825. He was a physician until he became professor of chemistry at the University of St. Petersburg in 1830. His initial research was the oxidation of sugars.

His main research was on Russian mineral and natural gas deposits in the Baku region on the Caspian shores. In 1834, he wrote a chemistry textbook that was adopted by students from many Russian schools and universities.

In 1840, he enunciated Hess's Law. This law states that in a chemical reaction the amount of heat produced is constant and independent of the number of reaction steps. In fact, it would be a special case of the general principle of energy conservation.

Hess published the book Fundamentals of Chemistry, one of the best chemistry texts in Russia for years.

Henri Hess died in St. Petersburg on November 30, 1850.