Heidelberg University, named after Ruprecht and Charles, known as Ruprecht-Karls-Universität Heidelberg, is the oldest and one of the most prestigious universities in modern Germany. Founded in 1386, it originally included four faculties. Most university buildings are located in the Old Town of Heidelberg, as well as in the districts of Bergheim and Neuenheimer Feld. Heidelberg University played a key role in the establishment of the League of European Research Universities and the Coimbra Group. It is associated with 56 Nobel Prize laureates.

In the 19th century, the university became a center for natural sciences, especially physics and chemistry. This was due to the development of German industry, which began in 1848 with the construction of railways. Germany had already been a leader in the mining industry since the late Middle Ages, and by the 1850s, textile and chemical production was developing, relying on local resources for the production of acids and alkalis. Although the Grand Duchy of Baden, where Heidelberg is located, did not have its own mineral resources, its industry thrived due to its proximity to major mining regions in Germany and its border location at the upper Rhine, near Switzerland and France. This contributed to the prosperity of production and trade, which, in turn, stimulated the development of the sciences necessary for industry. Heidelberg University was known for its outstanding scholars, attracting young researchers like Dmitri Mendeleev.

In Heidelberg, Dmitri Ivanovich Mendeleev began working in Robert Bunsen's laboratory, also attending university lectures. Bunsen, whom Mendeleev chose as his mentor, was one of the significant figures in the history of chemistry. He avoided participating in scientific disputes, preferring to focus on targeted research work that yielded more results than discussions. By the time Mendeleev arrived at his laboratory, Bunsen was known for his research on crocodile compounds and electrolytic aluminum, which he discovered in 1854.

Despite the warm welcome, Mendeleev did not work long with Bunsen. He explained his departure by saying that his desk neighbor, Karius, was working with sulfur compounds, the smell of which caused Mendeleev chest pain. Fume hoods were not yet a mandatory part of laboratories, and the lack of the ability to work with precise instruments also contributed to his departure.

After that, Mendeleev set about organizing his own laboratory. He intended to study liquids and ordered a new device for precise determination of specific gravity from Bonn mechanic Geisler, which became known in Russia as the 'Mendeleev Pycnometer.' To achieve maximum accuracy of scales and balances, he had them custom-made. Despite the limited funds allocated for his trip, Mendeleev was able to equip the laboratory to fully dedicate himself to work. As a result, he wrote and published studies on the capillarity of liquids, the expansion of liquids under the influence of temperature and pressure, as well as on absolute boiling temperatures.

Particularly interesting was the work on absolute boiling temperature. In the first half of the 19th century, this concept was not yet known; there was only a division of gases into those that could be condensed into liquid and those that were permanent, that is, non-condensable. However, the research of Cagnard de la Tour, Drioux, Mendeleev, and Andrews on critical temperatures showed that for each gas there is a temperature above which it cannot be converted into a liquid by any pressure. At this temperature, the movements of gas particles become so rapid that they cannot form even temporary bonds characteristic of the liquid state.

Mendeleev explained that for successes in molecular mechanics, which should explain the physical and chemical properties of substances, it is necessary to have accurate data on the weight of particles, the specific weight of solids and liquids, and its change when heated. This data allows one to judge the distance between the centers of particles. The weight and distance of particles are insufficient to solve the questions of the mechanics of solids and liquids, as the distances between particles are not so great that one can neglect their shape and size. The determination of the adhesion of bodies can serve as a means for successes in partial mechanics, as it is related to the measure of mutual attraction of particles, which determines physical and chemical phenomena.