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 (Ag
2Te), 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