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MOST IMPORTANT SCIENTIFIC DISCOVERIES
The law of active masses. History and essence of scientific discovery
Directory / The most important scientific discoveries The law of mass action is included in the scientific and educational literature as one of the basic laws of chemistry. The fact that the process of chemical interaction depends on the number of active masses was confirmed by facts coming from both the field of organic and inorganic chemistry. G. Rose (1851), R. Bunsen (1853), D. Gladstone (1855) provided material to prove the existence of reversible chemical transformations and the possibility of changing the direction of the reaction by selecting the appropriate conditions for its course. The French chemist Saint-Clair Deville (1818–1881) in 1857 proved that the decomposition of chemical compounds can begin even below the temperature of their complete decomposition. By the time of this discovery, Henri Etienne Sainte-Clair Deville was already a professor at the Higher Normal School in Paris. In 1861 he became a member of the Paris Academy of Sciences. It was St. Clair Deville who developed the first industrial method for producing aluminum (1854). The French scientist also proposed a new method for melting and refining platinum. He also synthesized various minerals. It is interesting that in 1869 St. Clair Deville was elected a corresponding member of the St. Petersburg Academy of Sciences. So, in the article of 1857 "On the dissociation, or spontaneous decomposition of substances under the influence of heat" (1857), St. Clair Deville showed that under the influence of temperature, water vapor decomposes into oxygen and hydrogen at the melting point of platinum (1750 ° C) and at the melting point of silver (950 °C). Later, in lectures on dissociation given in 1864 to the French Chemical Society, Saint-Clair Deville formulates the final conclusion of his experiments: "The transformation of water vapor into a mixture of hydrogen and oxygen is a complete change of state corresponding to a certain temperature, and this temperature is constant during the transition from one state to another, in whatever direction these changes may take place. This "phenomenon of spontaneous decomposition of water, I propose to call dissociation." It should be noted that this definition only covered cases "in which the decomposition takes place partially and at a temperature lower than the temperature which corresponds to the absolute destruction of the compound". The French scientist showed that some compounds, even the most stable ones, easily dissociate at high temperatures (1200–1500 °C). The chemical equilibrium established in this case can be controlled by changing the temperature and pressure. St. Clair Deville also proposed a method of "hardening" chemical reactions. “It turned out,” writes Yu. "cold-hot tube" was as follows. Through a porcelain tube heated to a high temperature, the test gas was slowly passed. In the center of the porcelain tube, a thin silver tube passed through which cold water flowed. When passing through a hot porcelain tube in the opposite direction, carbon monoxide on silver carbon was deposited in the tube, and silver chloride was obtained by passing hydrogen chloride.V. Saint Clair Deville associated chemical equilibrium with two interdependent processes: combination and decomposition. His works on thermal dissociation were of paramount importance for the further development of the theory of chemical equilibrium. "... The studies of Henri Saint-Clair Deville, devoted to the phenomenon of dissociation," wrote J. Dumas, "are the greatest acquisition not only of chemistry, but also of physics. Thanks to the discovery of this capital phenomenon (thermal dissociation. - Approx. Aut.), he discovered a new path in science - the path of convergence of chemical phenomena with purely physical ones. The work of St. Clair Deville on dissociation was highly valued by his successor, the Russian physical chemist N. N. Beketov. They constitute not only a "historical epoch in the development of chemistry", but also "a turn in the direction of the study of chemistry. Since then, the (almost abandoned) study of chemical phenomena has begun again (instead of the almost exclusive study of the composition and structure of compounds), that is, the study of static chemistry went side by side with the study of dynamic chemistry. Nikolai Nikolaevich Beketov (1827–1911) graduated from Kazan University in 1848. From 1859 to 1887 he was a professor of chemistry at Kharkov University. In 1886, Nikolai Nikolaevich became an academician of the St. Petersburg Academy of Sciences. The main works of the scientist are devoted to the study of the nature of chemical affinity, chemical equilibrium and thermochemistry. In 1864, Beketov organized a physical and chemical department at the Faculty of Physics and Mathematics of Kharkov University, where he himself gave a systematic course of lectures on physical chemistry. In 1859-1865, Beketov studied the dependence of the phenomena of displacement of some elements by others on external physical conditions (temperature, pressure, etc.). On the example of one of the reactions - the displacement of metals by hydrogen from solutions of their salts - he showed that "this action of hydrogen depends on the pressure of the gas and the strength of the metal solution, or, in other words, on the chemical mass of the recovered body." He found that "the chemical action of gases depends on pressure and, depending on the magnitude of the pressure, can even be performed in the opposite direction." The scientist clarifies the position by saying that the action of a gas is proportional to pressure or mass. Undoubtedly, the research data of the Russian scientist were of great importance for the development of the theory of chemical equilibrium and for the preparation of the discovery of the law of mass action. In 1862, the work of M. Berthelot and L. Pean de Saint-Gilles appeared, summarizing a large amount of factual material on the dependence of the limit of esterification and saponification reactions on the amounts of interacting substances - "Studies on Affinity. On the Formation and Decomposition of Ethers." The next step is taken by Henri Debret (1827-1888), a French chemist who worked in 1855-1868 as an assistant to St. Clair Deville at the Higher Normal School. In 1867-1868 a teacher at the École Polytechnique in Paris makes a generalization that the pressure of a gaseous constituent or constituents obtained in the process of dissociation is constant at any given temperature and does not depend on the amount of the original substance that has undergone decomposition. Debreux showed that in many cases when a solid dissociates, the dissociation pressure does not depend on the amount of substances present, but only on temperature. Initially, attempts were made to establish the affinity coefficients for each ratio of taken masses separately. However, later the idea arises to find a general way to calculate the equilibrium conditions for any amount of reactants. Kato Maximilian Guldberg (1836–1902), Norwegian physico-chemist, professor of technology at the University of Christiania (now Oslo), and Peter Waage (1833–1900), Norwegian chemist, professor of chemistry at the University of Christiania, presented the equilibrium in 1862–1867 reversible exchange reaction as the equality of two affinity forces acting in opposite directions. The authors mathematically formulated the law of mass action, building their theory on the general equilibrium condition. In doing so, they relied on the experimental data of M. Berthelot and Pean de Saint-Gilles, as well as their own results. They adhered to the mechanical interpretation of the nature of the forces of affinity adopted in the sixties. Guldberg and Waage wrote: “We believe that in order to determine the magnitude of chemical forces, it is necessary to study chemical processes always under such conditions that both of their opposite directions simultaneously manifest themselves ... If we assume that two opposite forces act in a given chemical process: one, tending form new substances, and the other is to restore the original compounds from new ones, then it becomes obvious that when these forces in the chemical process become the same, the system is in equilibrium. In 1867, in their monograph "Investigations into the Forces of Chemical Affinity", Guldberg and Waage showed that chemical reactions proceed both in the forward and in the reverse direction. "The force causing the formation of A and B increases in proportion to the affinity coefficient for the reaction A + B = A' + B', but, moreover, it depends on the masses of A and B. We deduced from our experiments that the force is proportional to the product of the acting masses two bodies A and B ... "Forces" of direct and reverse reactions are balanced..." This is the law of acting masses. Guldberg and Waage conclude their work as follows: “Although we have not solved the problem of chemical affinity, we hope that we have expressed a general theory of chemical reactions, namely the consideration of those reactions in which a state of equilibrium between opposite forces takes place ... The purpose of our work was to show , firstly, that our theory explains chemical phenomena in general, and, secondly, that the formulas based on this theory agree quite well with quantitative experiments ... All our desires would be fulfilled if, through this work, we had time to draw the serious attention of chemists to a branch of chemistry which has undoubtedly been too neglected since the beginning of this century." In 1879, a new article by Guldberg and Waage appeared - "On chemical affinity". Here, scientists give a molecular-kinetic explanation of chemical reactions and equilibria instead of ideas about the action of static "forces". Explaining the process of equilibrium of opposite reactions, the authors believe that “a simple assumption about the forces of attraction between substances or their constituent parts is not enough ... It is necessary to take into account the movement of atoms and molecules ... The state of equilibrium that occurs in such chemical processes is the state mobile equilibrium, since two opposite chemical reactions take place simultaneously: not only the formation of A' and B' proceeds, but also the reverse formation of A and B. If equal amounts of each of these pairs are formed per unit time, there is an equilibrium. Based on their interpretation of chemical equilibrium, Guldberg and Waage for the first time give a kinetic derivation of the law of mass action. They conclude that the reaction rate is determined by the probability of collision of interacting particles. In 1880, a large number of works appeared in support of the law of mass action. Subsequently, it was possible to establish the inapplicability of this law to nonideal systems. The "modernization" of the concentration formula made it possible to successfully apply the law of mass action to study the equilibrium of chemical reactions. Today, the law serves as the basic equation of chemical kinetics used to calculate technological processes. Author: Samin D.K.
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