Germain Henri Hess
Germain Henri Hess was a notable Swiss-born Russian chemist, born on August 7, 1802, in Geneva, Switzerland. He spent his early years in Russia, where he pursued an education in medicine and chemistry at the University of Tartu, later studying under the esteemed chemist Jöns Jakob Berzelius. Hess became a prominent figure in the scientific community after settling in St. Petersburg, where he established a modern chemical laboratory and contributed significantly to the field of thermodynamics.
Hess is best known for formulating Hess's law, which posits that the total heat change during a chemical reaction is the same, regardless of the pathway taken. This principle has been foundational in thermodynamics and has enduring applications in chemistry today. His research also included the discovery of saccharic acid and the principle of thermal neutrality, which was later theorized by Svante Arrhenius.
Throughout his career, Hess played a key role in advancing chemical education in Russia, authoring influential textbooks, and mentoring students. He passed away on December 12, 1850, leaving a lasting impact on the scientific community and paving the way for future research in thermodynamics.
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Germain Henri Hess
Swiss-born Russian chemist
- Born: August 7, 1802; Geneva, Switzerland
- Died: December 12, 1850; St. Petersburg, Russian Empire (now Russia)
Early nineteenth-century chemist Germain Henri Hess discovered the law of constant heat summation, which is a key ancestor of the first law of thermodynamics. Hess also investigated minerals, and contributed to education and research in chemistry in Russia.
Also known as: Hermann Heinrich Hess, German Ivanovich Gess
Primary field: Chemistry
Specialties: Thermodynamics; physical chemistry; analytical chemistry; organic chemistry
Early Life
Germain Henri Hess was born in Geneva, Switzerland, on August 7, 1802. His father was a painter and also taught French. Shortly after Hess was born, his father moved to Russia, where he took a position as French tutor and general manager at the farm of a Russian nobleman close to Moscow. In 1805, Hess and his mother, Louisa, relocated to Russia as well. Hess’s mother took a position as governess and he took classes with the children of the farm’s owner. His studies included natural sciences, humanities, and foreign languages.
At age fifteen, Hess went to Tartu (in contemporary Estonia), where he graduated from high school in 1822. In the fall, Hess enrolled at the University of Tartu to study medicine. He also attended lectures in chemistry, physics and geology, and enjoyed work in the chemistry laboratory. On October 3, 1825, Hess graduated with honors as medical doctor. For his thesis, he studied the chemical and medicinal properties of mineral water.
Impressed by Hess’s academic performance, his professors of chemistry, Gottfried Wilhelm Osann and Moritz von Engelhardt, recommended him for a postdoctoral scholarship. Soon after his graduation, Hess left for the University of Stockholm, where he studied with renowned chemist Jöns Jakob Berzelius.
Back in Russia, Hess settled as a physician in the Siberian city of Irkutsk in 1826. In Irkutsk, Hess specialized in obstetrics and ophthalmology. However, he also undertook scientific excursions to the Ural Mountains and Lake Baikal. He published his findings from these expeditions on which he studied minerals, salt deposits, and mineral waters.
Life’s Work
In 1828, Hess was elected as an adjunct faculty member at the Imperial Academy of Sciences in St. Petersburg. On March 5, 1829, Hess left Irkutsk for St. Petersburg. At the academy, Hess established a state of the art chemical laboratory. On August 11, 1830, Hess was promoted to become an extraordinary member of the Academy of Sciences.
In 1831, Hess became an inspector of courses at the new St. Petersburg Institute of Technology. That year, he published his two-volume Russian textbook, Fundamentals of Pure Chemistry. The book remained the standard Russian chemistry text until 1861. In St. Petersburg, Hess also taught at the University of St. Petersburg, the Michailovsky Artillery School, and the Petersburg Institute of the Corps of Mining Engineers.
Hess undertook a study of St. Petersburg’s Neva River, which was published in 1831. He also pursued his interest in minerals. Hess’s detailed analysis of disilver telluride (Ag2Te), which German mineralogist Gustav Rose first described in 1830, led to the compound being named hessite in his honor in 1843.
Around 1830, Hess began studying the amount of heat generated during chemical reactions. He hoped that analysis of the heat released during reactions might further scientists’ understanding of the composition of chemical compounds. In the winter of 1833, Hess began documenting the results of his first calorimetric or heat-measuring experiments.
On May 14, 1834, Hess was elected full member of the Academy of Sciences in St. Petersburg. For the thirty-two-year-old scientist, this was a major achievement. While Hess pursued his calorimetric studies, he also discovered saccharic acid when he oxidized sugars with nitric acid; he published this result in 1838.
Some of Hess’s most important discoveries were published in a series of articles from 1840 to 1842. In 1840, Hess discovered that no heat was gained or lost from the exchange reactions of neutral salts dissolved in water. He called this fact thermal neutrality.
Hess’s second major discovery would become known as Hess’s law. It has been defined as the law of constant heat summation. According to Hess’s law, the heat or energy released or consumed in a chemical reaction is always the same if the first and last conditions for the reaction are the same. For example, if the final reaction can be reached by different ways, the sum of the heat or energy gained or lost in the end will be the same for each variant of intermediate steps if the initial situation is the same. Hess showed this for the neutralization of sulfuric acid with ammonia. He determined that regardless of how much water is added to dilute the acid in a preliminary step, the heat gained at the final step of the reaction is always the same.
Based on this discovery, Hess developed the idea that the amount of heat generated or lost in a chemical reaction is an indication of the chemical affinity of the substances involved.
In 1848, Hess fell sick in St. Petersburg. He finally succumbed to his illness and died on December 12, 1850. He was buried at the Smolensk cemetery in St. Petersburg.
Impact
Hess’s contributions to the field of thermodynamics have been widely acknowledged. His law laid the foundation for further research into the heat, or energy, of closed systems. His ability to develop a general law from the results of his methodical research is still a model for achieving success in scientific inquiry and endeavor.
Contemporaries were quick to grasp the significance of Hess’s thermodynamic discovery. His articles, which appeared first in the Franco-Russian scientific journal Bulletin scientifique Académie impériale des sciences, were quickly republished in the more widely disseminated and read Poggendorffs Annalen der Physik, the influential journal that would later publish Albert Einstein’s papers of 1905.
Hess’s law has been called a key forerunner of the first law of thermodynamics. Its validity has stood up in contemporary chemistry. It has been particularly useful for calculating the total amount of heat or energy of complicated chemical processes where a direct measurement of the energy values at the beginning and end of the process is defined. In this case, using Hess’s law, the total of energy change can be calculated by adding up the amount of energy changes from each intermediary step.
Hess’s observation of thermal neutrality, derived from his experiments with neutral salts diluted in water, received its theoretical explanation only after Hess’s own lifetime. In 1887, Swedish scientist Svante Arrhenius developed his theory of electrolytic dissociation. This explained the reason for Hess’s observation, as the ions of the salts did not react with each other, creating no heat.
Hess not only discovered a thermodynamic law but also contributed to the education of Russian and international students in St. Petersburg. He showed a wide range of scientific interests and was part of a new generation of chemists in the first half of the nineteenth century who took part in advancing the revolution of chemical knowledge.
Bibliography
Kondepudi, Dilip. Introduction to Modern Thermodynamics. New York: Wiley, 2008. Print. Places Hess’s pioneering work and Hess’s law in the context of the development of the first law of thermodynamics. Discusses Hess’s original experiment leading to his discovery.
Leicester, Henry M. “Germain Henri Hess and the Foundations of Thermochemistry.” Journal of Chemical Education 28.11 (1951): 581–83. Print. Presents a portrait of Hess’s life and discusses the scientific contribution of Hess’s law toward the development of the first law of thermodynamics.
Sandler, Stanley I., and Leslie V. Woodcock. “Historical Observations on Laws of Thermodynamics.” Journal of Chemical and Engineering Data 55.10 (2010): 4485–90. Print. Credits Hess for his pioneering work toward the articulation of laws of equilibrium thermodynamics and outlines the development of these laws based on his initial research and subsequent theory.
Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change. 6th ed. New York: McGraw-Hill, 2011. Print. Explains Hess’s law in detail and places it in the context of contemporary thermodynamics.