Inorganic Chemistry

INORGANIC CHEMISTRY. The name I. ch., or chemistry of inorganic mineral compounds, was given in opposition to organic chemistry at a time when it was believed (see Organic Chemistry) that organic compounds, unlike inorganic ones, could only be formed in living organisms of plants and animals.-- The history of I. ch. is at the same time the history of chemistry in general. Only gradually did individual chapters develop into independent chemical disciplines (analytical, organic, physical chemistry) with various subdivisions, some of which also became independent (for example, colloid chemistry). The initial history of chemistry is predominantly the history of I. ch. Strictly scientific chemistry begins with Lavoisier, but the facts that formed the basis of Lavoisier's chemical views were experimentally obtained even earlier, mainly during the period of phlogiston chemistry. A number of the greatest researchers of the phlogiston period made extremely important discoveries without which the further development of chemistry would have been unthinkable. In the terms of phlogiston theory were the works of Priestley and Scheele, who discovered oxygen, and all the works of Cavendish, who studied hydrogen as a special gas, carbon dioxide, established the composition of water and air. The essence of phlogiston theory is as follows: according to the teaching of Stahl, the founder of this theory, all combustible bodies contain a common constituent part--phlogiston, which volatilizes during combustion and calcination. The more easily a substance burns, the more phlogiston it contains; for example, coal, which burns almost completely, was considered as almost pure phlogiston. To restore the original substances, it is necessary to add phlogiston to the combustion product. In this way, metals are obtained from "earths" (oxides); the source of phlogiston can be coal. Thus, a metal consists of "earth" and phlogiston; during calcination, phlogiston flies away, leaving "earth" (oxide); when the latter is heated with coal, metal is obtained again. These are reactions now known as oxidation and reduction. The phlogiston theory then explained the known facts. However, even during the phlogiston period, it was pointed out that the weight of a body during calcination, combustion should decrease, during the reverse process - increase, while in reality the opposite takes place. But in view of the absence at that time of quantitative research of chemical phenomena, this was not initially given sufficient attention. Later, when it was already impossible to ignore this fact, various explanations were proposed: for example, some assumed that "earths" (oxides), "earths" have a greater specific gravity than metals; others believed that phlogiston has negative weight, others simply believed that the explanation of such a phenomenon is a matter of physics, not chemistry. Much later, when the phlogiston theory had long since fallen, it was pointed out that phlogiston could be considered as energy, released or absorbed during reactions. M. V. Lomonosov and later, independently of him, Lavoisier, by applying quantitative research methods, clarified the contradictions that had arisen on the basis of phlogiston theory. The theory of combustion correctly explained the increase in weight during calcination and combustion of bodies. Lomonosov made many discoveries, subsequently made by Lavoisier. Lomonosov was the first professor of chemistry as a separate subject from medicine and natural history, and the founder of the first chemical laboratory in Russia. Lomonosov, even before Lavoisier, applied the law of conservation of mass to physics and chemistry. In his "Elements of Mathematical Chemistry" Lomonosov applied the laws of mechanics to chemistry, striving to turn chemistry into a part of mechanics; he proposed the corpuscular theory of matter; he owns a number of experiments and theoretical reasoning on the theory of solutions. With all these works, Lomonosov laid the foundation for a new branch of chemistry. Lomonosov conducted a series of experiments on the causes of oxidation of metals, anticipating the application of quantitative methods in chemistry and Lavoisier's theory of combustion. The main provisions of the theory of combustion consist in the recognition that bodies burn in "pure air" (oxygen) and the gain in weight of the body is equal to the loss in weight of the air; at the same time, metals pass into "earths", combustible bodies into acids. During the combustion of hydrogen, Lavoisier also expected and sought acid, and only Cavendish showed that during the combustion of hydrogen water is formed, on the basis of which Lavoisier determined the qualitative and approximate quantitative composition of water. The atomic theory, developed by Dalton, the law of multiple proportions, derived by him, the law of constant composition and conservation of substance, Avogadro's rule made possible the further correct development of chemistry. According to Dalton, each element consists of homogeneous atoms of unchanging weight; complex bodies are formed by the combination of atoms of elements in simple numerical ratios; the molecular weight of a compound is equal to the sum of the atomic weights of the elements it contains. The law of multiple proportions was derived by Dalton from the determination of the composition of ethylene and methane, carbon monoxide and CO₂, nitrous and nitric oxides, nitric and nitrous acids. Dalton also found the relative atomic weights of elements, based on the quantitative ratios in which elements enter into compounds; Dalton's atomic weights do not correspond to modern ones, but the principle of determination was given correctly.-Gay-Lussac (law of volumes) and Duma with their works supported the atomic theory. Especially much was done to strengthen and develop the atomic theory by Berzelius. Berzelius introduced a system of notation for elements close to the modern one, investigated the oxidation states of metals and metalloids, gave mostly correct atomic weights of elements, simultaneously with Davy developed the electrochemical theory. According to this theory, atoms possess electrical energy; each particle has two poles with different amounts of opposite electricity-positive and negative. During electrolysis, some substances are released at the positive, others at the negative pole. Unequal polar tension of particles is the cause of chemical affinity. Electropositive elements give with oxygen basic compounds, electronegative ones-acidic. Berzelius arranged all elements in a row, starting with oxygen, followed by metalloids, hydrogen, metals, ending with Na and K. Berzelius' dualistic theory explained all the facts then available, but soon a number of new facts gradually began to undermine this theory. Thus, according to Lavoisier and Berzelius, acids and their salts must necessarily contain oxygen, but the discovery of halogen acids showed that the presence of oxygen is not necessary, that hydrogen is the carrier of acidic properties, capable of being replaced by a metal. The theory of hydrogen acids and the theory of polybasic acids (Graham, Liebig) erased the line between oxygen and hydrogen acids and established that both types of acids are similar to each other in properties in all respects. A number of facts of replacement of hydrogen by halogen (metallesia) broke a breach in the dualistic theory, and in its place came the unitary theory, which considered a chemical compound as a whole. These new views developed mainly on the basis of organic chemistry; as for I. ch., by this time a special branch of chemistry-physical chemistry-begins to definitely isolate itself, to which should be attributed works of such paramount importance as those of van't Hoff and Ostwald on the theory of solutions, Arrhenius (theory of electrolytic dissociation) and others. - The area of research proper to I. ch. now narrows. First of all, the subject of I. ch. is the discovery and study of a long series of new elements. Recently, after the discovery and study of the so-called "noble" gases (argon, helium, neon, krypton, xenon) and radioactive substances, the study of rare earths has become one of the main tasks of I. ch. Another major area of it is the study of complex compounds, but to a large extent this area should be attributed to physical, analytical and organic chemistry. The study of radioactive substances also constitutes the subject of I. ch., but the numerous theoretical questions arising from the study of radioactive substances are closely related to physical chemistry and physics (radioactive decay, structure of matter). The same can be said about isotopes; their study raised a number of questions, the solution of which belongs to both physics and physical chemistry, for example, the question of element and atom; the content of these concepts essentially changes compared to the classical one. The abundance of inorganic compounds, the diversity of forms, force in one way or another to classify these compounds. The basis for the classification of elements is the periodic system of chemical elements by D. I. Mendeleev (see Periodic system of elements); as for the classification of compounds, I. ch. distinguishes basic oxides (oxides, suboxides) and acidic oxides (anhydrides), which give with water hydrates: suboxides, oxides, on the one hand, and acids-on the other.

The products of the interaction of these oxides are salts (normal, acidic, basic). A more detailed division of these major groups (bases, acids, and salts) is closely connected with the questions of nomenclature of inorganic compounds. The question of Russian nomenclature has its own history. At the end of the 18th and beginning of the 19th centuries, Russian chemists had to translate chemical terms into Russian. Severgin in his book "Assaying Art" (St. Petersburg, 1801) uses the following terms: acid-forming, water-forming, suffocating, carbon substance (O, H, N, C), known, talc, clay, siliceous earth (CaO, MgO, Al₂O₃, SiO₂), vitriol normal salts (neutral sulfates), saltpeter normal salts (nitrates), salt normal salts (hydrochlorides), boron, arsenic normal salts (salts of boric, arsenic acids), wolfham acid (tungstic), acids of growths (vegetable), compositions of metals (alloys). Scherer (1807) calls O, H, N acid-forming, water-forming, saltpeter-forming; carbonates are called carbons, sulfates - sulfurs [clay sulfur, Al₂(SO₄)₃], sulfites - sulfites, nitrates - saltpeters. Giese (1813) calls C carbon principle, PH₃, H₂S, CH₄ - phosphorus, sulfur, carbon hydrogen, copper hydroxide - copper hydrate. In the book of Iovsky "Chemical Equations" (St. Petersburg, 1827) there are such terms: acid-forming, water-forming, salt-forming (O, H, Cl), iron (Ba), alum (Al), oxide and dioxide of salt-forming (Cl₂O, ClO₂), salt-formic acid and oxidized salt-formic acid (Cl₂O₅, Cl₂O₇), air-forming ammonium (NH₃), first-salt and double salt mercury (HgCl, HgCl₂), water-forming-iodic acid (HJ), bodies "instrumental" (organic substances) and etc. N. Shcheglov (1830) in his chemistry guide uses the following terms: silicium (Si), clay-earth (Al), lime-earth (Ca), bitter-earth (Mg), beryllium (Be), potash (K), soda (Na), selenium (Se), wolfham (W), first and second sulfuric iron (FeS, FeS₂), first and second chloric acid mercury (HgCl, HgCl₂). In 1831-33 Hess in his guide "Foundations of Pure Chemistry" gave a nomenclature much of which has been preserved in modern nomenclature. In 1868 Mendeleev, making some changes, introduced this nomenclature into "Foundations of Chemistry". In 1869 V.V. Markovnikov at the 2nd Congress of Russian Naturalists and Physicians raised the question of nomenclature. N.E. Lyaskovsky made a report on the question of nomenclature; on the proposal of A.M. Butlerov a special commission was created, which in 1870 in the Chem. Soc. made a report in which it pointed to the lack of essential need for a radical change in chemical nomenclature. The Chemical Society postponed the decision of this question. Later the "International Association of Chem. Soc." raised the question of nomenclature in general. At the end of the 1920s the question of Russian nomenclature of inorganic compounds arose again. In the Russian Physico-Chemical Society and at the V Mendeleev Congress named after A.M. Butlerov in Kazan A.Kh. Bork, A. Sementsov, E.Kh. Fritsman made reports on the question of the need for reform of Russian inorganic nomenclature, and the congress allocated a special commission, which together with the permanent bureau of congresses should develop the question for the next - VI congress, to be held in Kharkov in 1931. In the reports in the chemical societies and at the V Mendeleev Congress it was pointed out the lack of a strictly maintained scientific Russian nomenclature of inorganic compounds, as well as the fact that the nomenclature we use does not correspond either to the number of compounds or to the requirements of rationality, does not express valence. The nomenclature proposed by Stock and adopted in some German guides is not entirely convenient for translation into Russian; the peculiarity of Stock's nomenclature lies in the designation of valence by a number placed after the name, e.g. Hg₂O - oxide of mercury (1), HgO - oxide of mercury (2), Mn₂O₇ - oxide of manganese (7), SO₃ - oxide of sulfur (6) and etc. Special difficulties are encountered in the designation of complex compounds; the nomenclature of Werner in Russian translation does not always sound Russian, and it is necessary to somewhat modify it in accordance with the properties of the Russian language. Laboratories of inorganic chemistry - see Chemistry.