Germain Hess
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Germain Henri Hess (; 7 August 1802 – ) was a Swiss-Russian chemist and doctor who formulated Hess' law, an early principle of thermochemistry.


Early life and education

Hess was born on 7 August 1802 in
Geneva Geneva ( , ; ) ; ; . is the List of cities in Switzerland, second-most populous city in Switzerland and the most populous in French-speaking Romandy. Situated in the southwest of the country, where the Rhône exits Lake Geneva, it is the ca ...
,
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
(Switzerland after 1815). His father was an artist and in 1805 moved the family to the Russian Empire to work as a tutor to a rich family. His mother was a tutor as well and Hess learned German and French at home. In 1817, his family moved to
Dorpat Tartu is the second largest city in Estonia after Tallinn. Tartu has a population of 97,759 (as of 2024). It is southeast of Tallinn and 245 kilometres (152 miles) northeast of Riga, Latvia. Tartu lies on the Emajõgi river, which connects the ...
,
Russian Empire The Russian Empire was an empire that spanned most of northern Eurasia from its establishment in November 1721 until the proclamation of the Russian Republic in September 1917. At its height in the late 19th century, it covered about , roughl ...
(now
Tartu Tartu is the second largest city in Estonia after Tallinn. Tartu has a population of 97,759 (as of 2024). It is southeast of Tallinn and 245 kilometres (152 miles) northeast of Riga, Latvia. Tartu lies on the Emajõgi river, which connects the ...
,
Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...
), where he went to a private school for two years, and then to Dorpat Gymnasium, which he finished in 1822. In autumn of the same year Hess studied medicine at the University of Dorpat. During that time, the chemistry department was responsible for the Chemistry courses of the Medicine and Pharmacy departments and Professor Gottfried W. Osann was giving the lectures in German (an obvious advance for Hess). Under Osann's supervision, Hess made chemical analyses, but also had an interest in the lectures of Professor of Physics Georges-Frédéric Parrot and Professor of Mineralogy Moritz von Engelhardt. 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''. He qualified as a physician in 1825. By application of Professors Osann and Engelhardt, Hess was sent to Sweden, to visit Swedish chemist
Jöns Jakob Berzelius Jöns is a Swedish given name and a surname. Notable people with the given name include: * Jöns Jacob Berzelius (1779–1848), Swedish chemist * Jöns Budde (1435–1495), Franciscan friar from the Brigittine monastery in NaantaliVallis Grati ...
. After this meeting Hess turned once and for all to chemistry. On his return to Russia, Hess joined an expedition to study the
geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
of the
Urals The Ural Mountains ( ),; , ; , or simply the Urals, are a mountain range in Eurasia that runs north–south mostly through Russia, from the coast of the Arctic Ocean to the river Ural (river), Ural and northwestern Kazakhstan.
before he was appointed a medical doctor at
Irkutsk Irkutsk ( ; rus, Иркутск, p=ɪrˈkutsk; Buryat language, Buryat and , ''Erhüü'', ) is the largest city and administrative center of Irkutsk Oblast, Russia. With a population of 587,891 Irkutsk is the List of cities and towns in Russ ...
. According to the regulations of that time, new doctors had to practice at a Russian frontier town after having graduated. Hess went to
Irkutsk Irkutsk ( ; rus, Иркутск, p=ɪrˈkutsk; Buryat language, Buryat and , ''Erhüü'', ) is the largest city and administrative center of Irkutsk Oblast, Russia. With a population of 587,891 Irkutsk is the List of cities and towns in Russ ...
in August 1826.


Contributions to chemistry

In 1830, Hess took up chemistry full-time, researching and teaching, and later became an adjunct professor of Chemistry at the St. Petersburg Academy of Sciences. His most famous paper, outlining his law on thermochemistry, was published there in 1840. His principle, a progenitor for the
first law of thermodynamics The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. For a thermodynamic process affecting a thermodynamic system without transfer of matter, the law distinguishes two ...
, came to be called Hess' 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. Like most of his colleagues, Hess was primarily an experimental chemist interested in the discovery and analysis of new substances. However, he also developed a strong interest for theoretical investigations. In particular, he wondered how
chemical affinity In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds. Chemical affinity can also refer to the tendency of an atom or compound to com ...
relates to heat in chemical reactions. His experiments on various hydrates of
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
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 The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be Conservation law, ''conserved'' over time. In the case of a Closed system#In thermodynamics, closed system, the principle s ...
two years before Julius Robert von Mayer stated a more general principle, in 1842. Hess was fully aware of the importance of his own contribution. In 1842, Hess proposed the law of thermoneutrality, which states that no heat is evolved in the exchange reactions of neutral
salts In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions (anions), which results in a compound with no net electric charge (electrically neutral). ...
in
aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water ...
. A full explanation would only be given 45 years later, in terms of electrolytic dissociation, by the Swedish chemist
Svante Arrhenius Svante August Arrhenius ( , ; 19 February 1859 – 2 October 1927) was a Swedish scientist. Originally a physicist, but often referred to as a chemist, Arrhenius was one of the founders of the science of physical chemistry. In 1903, he received ...
. After these two major discoveries, Hess was influential in the development of chemistry in Russia. His book ''Osnovania Chistoy Khimii'' (''Fundamentals of Pure Chemistry'') went through seven editions and remained the standard Russian textbook for undergraduate chemistry until 1861. Hess was active as a teacher and mentor of young scientists, until his poor health forced him to retire, in 1848.


Later research and final days

Hess' investigation of minerals included the analysis of silver telluride (Ag2Te), which was named hessite in his honour. He also discovered that the
oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
of sugars yielded saccharic acid. Hess died prematurely in 1850, at the age of 48, in St. Petersburg. He was buried at Smolenskoe Lutheran cemetery.


References


Further reading

* * {{DEFAULTSORT:Hess, Germain Henri 1802 births 1850 deaths Swiss emigrants to the Russian Empire Chemists from the Russian Empire Saint Petersburg State Institute of Technology alumni Full members of the Saint Petersburg Academy of Sciences Burials at Smolensky Lutheran Cemetery