History of the development of ideas about adsorption in the late 18th and 19th century
In the history-chemical literature there is almost no information about the development of adsorption in the late 18th and 19th century, the original works of researchers are practically not analyzed. This article is the first attempt to give a general outline of the development of adsorption studies in the period under consideration, analyzing the original work of scientists. The article shows the first experiments on the adsorption of gases in the works of C.W. Scheele and A.F. Fontana during the rapid development of pneumatic chemistry. They were the first to experimentally investigate the adsorption of many gases with coal. J.T. Lowitz and D.M. Kehl were the first scientists who investigated the adsorption of coal in a liquid phase and suggested using this phenomenon for many practical laboratory and industrial purposes. The article shows that in the 18th century the first theories of adsorption began to appear, such as phlogistic, mechanical (physical), and chemical at the gas-solid and liquid-solid boundaries. In the 19th century, researchers first pointed out the fact of heat release during gas adsorption, and also determined the heats of adsorption. Scientists have found that the magnitude of adsorption is influenced by many factors: the nature of the adsorbed substance and the adsorbent, the physical structure of the adsorbent, the size of its surface, as well as temperature and pressure. In the experiments of scientists it was found that the heat of adsorption of various gases on the coal exceeds the heat of liquefaction. In addition to the adsorption of gases by solids, the absorption of gases by liquids, as well as mixtures of gases by solid sorbents and liquids using the laws of Henry and Dalton, was also studied. Also, the adsorption of gases by glass surfaces was investigated. H. Kayser was clearly formulated many factors affecting adsorption. The article also shows the beginning of the study of the phenomenon of capillary condensation, and its mathematical description by scientists. The attempts of a theoretical description of the adsorption process are also shown. The 19th century scientists graphically constructed isotherms (H. Kayser, P. Chappuis) and isobars (P. Chap-puis) of adsorption and introduced the first linear mathematical dependencies to describe them (H. Kayser), which are still used. The most important research and achievements of scientists of the 19th century are summarized in this article.