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


Early life and education

Hess was born on 26 July (7 August) in
Geneva Geneva ( ; french: Genève ) frp, Genèva ; german: link=no, Genf ; it, Ginevra ; rm, Genevra is the List of cities in Switzerland, second-most populous city in Switzerland (after Zürich) and the most populous city of Romandy, the French-speaki ...
,
Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
. His father was an artist and in 1805 moved the family to Russia to work as a tutor to a rich family. His Swiss-born mother was a tutor as well and Hess had the benefit of learning German and French at home. In 1817, his family moved to Dorpat,
Russian Empire The Russian Empire was an empire and the final period of the Russian monarchy from 1721 to 1917, ruling across large parts of Eurasia. It succeeded the Tsardom of Russia following the Treaty of Nystad, which ended the Great Northern War. ...
(now
Tartu Tartu is the second largest city in Estonia after the Northern European country's political and financial capital, Tallinn. Tartu has a population of 91,407 (as of 2021). It is southeast of Tallinn and 245 kilometres (152 miles) northeast of ...
,
Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, a ...
), 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 Otto Moritz (I) Ludwig von Engelhardt ( - ) was a Baltic German mineralogist. He was a member of the Engelhardt family. Biography He was born in 1778 in his family'manor Wiesoan estate in Viisu, Viisu, Estonia. He studied Physics and Chemistry a ...
. 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 Gratiae ...
. 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 Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...
of the
Urals The Ural Mountains ( ; rus, Ура́льские го́ры, r=Uralskiye gory, p=ʊˈralʲskʲɪjə ˈɡorɨ; ba, Урал тауҙары) or simply the Urals, are a mountain range that runs approximately from north to south through European ...
before he was appointed a doctor at
Irkutsk Irkutsk ( ; rus, Иркутск, p=ɪrˈkutsk; Buryat language, Buryat and mn, Эрхүү, ''Erhüü'', ) is the largest city and administrative center of Irkutsk Oblast, Russia. With a population of 617,473 as of the 2010 Census, Irkutsk is ...
. 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 mn, Эрхүү, ''Erhüü'', ) is the largest city and administrative center of Irkutsk Oblast, Russia. With a population of 617,473 as of the 2010 Census, Irkutsk is ...
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 The Russian Academy of Sciences (RAS; russian: Росси́йская акаде́мия нау́к (РАН) ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across t ...
. 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, adapted for thermodynamic processes. It distinguishes in principle two forms of energy transfer, heat and thermodynamic work for a system of a constant amoun ...
, 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. 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 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 ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
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 In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be ''conserved'' over time. This law, first proposed and tested by Émilie du Châtelet, means th ...
two years before
Julius Robert von Mayer Julius Robert von Mayer (25 November 1814 – 20 March 1878) was a German physician, chemist, and physicist and one of the founders of thermodynamics. He is best known for enunciating in 1841 one of the original statements of the conservation ...
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 Exchange may refer to: Physics *Gas exchange is the movement of oxygen and carbon dioxide molecules from a region of higher concentration to a region of lower concentration. Places United States * Exchange, Indiana, an unincorporated community * ...
of neutral salts 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, or sodium chloride (NaCl), in water would be re ...
. A full explanation would only be given 45 years later, in terms of
electrolytic dissociation An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon diss ...
, by the Swedish chemist Svante Arrhenius. 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's investigation of minerals included the analysis of
silver telluride Silver telluride (Ag2Te) is a chemical compound, a telluride of silver, also known as disilver telluride or silver(I) telluride. It forms a monoclinic crystal. In a wider sense, ''silver telluride'' can be used to denote AgTe (silver(II) telluride ...
(Ag2Te), which was named
hessite Hessite is a mineral form of disilver telluride (Ag2Te). It is a soft, dark grey telluride mineral which forms monoclinic crystals. It is named after Germain Henri Hess (1802–1850). Hessite is found in the US in Eagle County, Colorado and in ...
in his honour. He also discovered that the
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
of sugars yielded
saccharic acid Saccharic acid, also called glucaric acid, is a chemical compound with the formula C6H10O8. It is derived by oxidizing a sugar such as glucose with nitric acid. Hess died prematurely in 1850, at the age of 48, in St. Petersburg. He was buried at
Smolenskoe Lutheran cemetery The Smolenskoye Cemetery (in German ''Smolensker Friedhof'') is a Lutheran cemetery on Dekabristov Island in Saint Petersburg, Russia. It is one of the largest and oldest non-orthodox cemeteries in the city. Until the early 20th century it was on ...
.


Further reading

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References

{{DEFAULTSORT:Hess, Germain Henri 1802 births 1850 deaths Russian chemists Saint Petersburg State Institute of Technology alumni Full members of the Saint Petersburg Academy of Sciences Burials at Smolensky Lutheran Cemetery