Chemistry

Chemistry, the science of substances, their transformations, interaction, and the phenomena that occur during these processes. The determination of the basic concepts with which Chemistry operates, such as atom, molecule, element, simple substance, reaction, and others, the study of molecular, atomic, and equivalent weights, and the investigation of the general laws governing simple and complex substances, is the domain of general Chemistry. The differences in properties of substances containing carbon from compounds of other elements, the special laws and the large number of known carbon compounds have led to the separation of Chemistry into the chemistry of carbon—organic chemistry (see)—from inorganic chemistry (see), which studies compounds of the remaining elements. Some branches of these sciences in turn have developed into independent disciplines, such as biological chemistry (see), chemistry of reactive substances, chemistry of rare elements, and others. From the standpoint of the methods used by Chemistry for studying substances, the following are distinguished: analytical chemistry, which aims to determine the composition of a given substance, for which it decomposes it into its constituent parts, isolates pure substances from them, and determines of what elements they are composed (qualitative analysis), in what quantities these elements are present (quantitative analysis), and how they are connected to each other. Analytical Chemistry solves these questions by studying the reactions of the given substance with other already known substances (reagents). The conclusions and findings of analytical Chemistry are verified by synthetic Chemistry, which, guided by the data of analysis and general laws, seeks to construct, obtain a substance, starting from simpler substances whose structure is known, or from elements. Synthetic Chemistry not artificially obtains substances found in nature but also prepares completely new substances, sometimes possessing very valuable properties (syntheses of many dyes, pharmaceutical preparations, explosives, chemical warfare agents, etc.). The application of physical methods to the study of substances and chemical reactions led to the creation of physical chemistry (see), a discipline that encompasses chemical phenomena with mathematical laws and in turn breaks down into a number of disciplines: thermochemistry, electrochemistry, photochemistry, and others. The change in properties of a substance depending on its degree of subdivision, dispersion, and the very widespread occurrence in nature of substances in a state of finest subdivision, in a colloidal state—served as the reason for the separation into an independent discipline of another branch of theoretical Chemistry—colloidal chemistry (see Colloids, colloidal chemistry). The achievements and conclusions of theoretical Chemistry form the basis of applied Chemistry, which also divides into a number of branches, depending on the field in which it finds application. Thus, technical Chemistry studies the most appropriate methods for obtaining various substances in practice. Agrochemistry investigates the chemical composition and properties of various soils in connection with the cultivation of certain plants on them, and considers the rational use of fertilizers. Food Chemistry studies food products from the point of view of their nutritional value, researches their wholesomeness, detects falsifications, and explores the possibility of replacing one product with another (the problem of substitutes). Pharmaceutical chemistry (see) deals with the synthesis of medicinal substances and clarifies the connection between the composition and structure of a substance and its effect on the organism. Forensic chemistry (see), by revealing poisons and impurities of foreign substances in various products and organs, contributes to the solving of crimes. Some branches of technical Chemistry, having given rise to special branches of industry, have grown into special disciplines, such as: chemistry of dyes, chemistry of artificial fiber, chemistry of rubber, etc. If Chemistry in its development must use data and resort to the help of mathematics, mechanics, and mainly physics, with which Chemistry in some branches, such as in the doctrine of atomic structure, is inextricably fused, then conversely: the data of Chemistry are widely used in a number of disciplines. The development of geology and mineralogy is in close connection with the chemical investigation of minerals, useful minerals, and rocks. Botany in its major branches—plant physiology and agronomy—is based on the data of Chemistry. Microbiology, dealing with the change of substances under the influence of microorganisms, thus comes into close contact with Chemistry. Medicine in its most diverse branches makes wide use of the successes of Chemistry. Biological Chemistry studies the processes occurring in the organism from a chemical point of view. Physiology, pharmacology, pharmacy, chemotherapy, experimental hygiene, and a number of other disciplines that study the transformations of substances in the organism or their interaction with the organism are thus in close connection with Chemistry. Brief outline of the development of Chemistry. The period of initial acquaintance with chemical phenomena, the period of accumulation of disparate experimental data, individual observations, facts began in Egypt, where in the hands of priests were gathered information about the processing of metals, the production of glass, enamel, the preparation of alloys, medicines, methods of embalming corpses. All these processes were accompanied by a mystical ritual, kept secret, and apparently the name Chemistry originated from the Egyptian word chemi, meaning black, dark. This period continued with the Arabs (8-9th centuries), who called the science of the preparation of alloys, the purification of tin, lead, methods of coloring, the multiplication of gold, the preparation of medicines, love potions, etc., alchemy (see). From the Arabs, alchemy passed to Europe (13-14th centuries). The expansion of trade relations and the increase in the value of gold in trade transactions brought to the forefront the problem of obtaining gold from other substances. Guided by the ideas of Aristotle and widely using experiment, alchemists in their search for the philosopher's stone for the transformation of substances and elixirs that give health and youth, accumulated a wealth of experimental material, which is the main significance of this era. The works of Boyle (1627-1691), who placed experiment in the first place, not preconceived ideas, open a new era in the development of Chemistry. Studying the decomposition of substances, Boyle arrives at the concept of a chemical element as a simple substance that does not undergo further decomposition. The development of industry (17th and beginning of 18th centuries) and in particular metallurgy focused the attention of chemists of that time on the phenomena of oxidation and reduction of metals, the phenomena of combustion, and the accumulated facts inevitably required generalization, without which further development was impossible. Such a generalization was the theory of phlogiston by G. Stahl (1660-1734) (see Inorganic Chemistry), which served as a guiding thread in further research for almost a whole century. By this time, the young, then revolutionary class—the bourgeoisie—was replacing feudalism. The end of the 18th century is characterized by the rapid growth of productive forces and the development of natural sciences; in Chemistry we have a whole galaxy of talented chemists. Cavendish (1766) discovers hydrogen, Priestley (1774) obtains and describes oxygen, Scheele—chlorine and a number of organic compounds, D. Rutherford (1772) discovers nitrogen. The theory of phlogiston in its development accumulates a number of contradictions, and Lavoisier (1743-1794), based on the experimental material of the theory of phlogiston, refutes the latter, discovering in the oxygen obtained by Priestly the real opposite of phlogiston. By introducing a strictly quantitative method into Chemistry (weighing substances before and after reaction), Lavoisier substantiates the correct theory of oxidation and experimentally confirms the law of conservation of matter, formulated earlier by Lomonosov (1711-1765). The quantitative researches of Richter (1762-1807), Bergman, Wenzel and other chemists led to the discovery of the laws of constant composition, equivalents, and finally Dalton (1766-1844), discovering the law of multiple proportions, sees in it experimental proof of the atomic theory of the structure of matter, a theory that underlies all concepts of modern Chemistry. The research of G. Gay-Lussac (1805) and Avogadro (1811) on the volumes of reacting gases contributed to the further development of the atomic and molecular theory of matter. W. Prout (1785-1850) went even further and on the basis of simple ratios observed in some atomic weights, concluded about the existence of atoms of primitive matter, from which all atoms of elements are built. Prout's hypothesis was completely abandoned after more accurate determinations of atomic weights, made by Stas (1813-1891), and only in modern Chemistry after the discovery of isotopes (see) this hypothesis found brilliant confirmation in the electronic theory of atoms. The works of Berzelius (1779-1848) had a great influence on the further development of Chemistry, who put forward the electrochemical theory of affinity and determined with great accuracy for that time the atomic weights of the then known elements. He also introduced modern chemical symbolism. The transition from handicraft to machine production influenced the development of metallurgy, which in turn required high-quality coal. The coal tar obtained in the coking of coal gave a number of substances for the rapid development of the organic chemical industry, first of all dyes needed for the textile industry. Closely connected with the above is the rapid development of organic Chemistry starting from the 1840s of the 19th century.

(the works of Gerhardt in France, Berthelot in England, Faraday in England, Liebig, Wöhler, Bunsen, Kekulé in Germany, and Voskresensky, Zinin, Butlerov in Russia). The basic concepts of the difference between an atom and a molecule, atomic weight and equivalent are established (the works of Laurent, Gerhardt, Cannizzaro). The generalization of the vast material of chemistry was the periodic law, discovered by D. I. Mendeleev (1837-1907). The periodic system of elements (see) not only allowed for the systematization of existing material, but also predicted a number of elements discovered later, indicated the connection existing between elements, and served as the basis for all modern teaching on the structure of atoms. The end of the 19th century and the beginning of the 20th century is characterized by the development of physical chemistry. The laws found by thermochemistry made it possible for the first time to approach the determination of chemical affinity from a quantitative point of view. The theory of solutions by van't Hoff, the theory of electrolytic dissociation by Arrhenius served as the foundation for the creation of the teaching on ions (see). The discovery of X-rays, the phenomena of radioactivity, isotopes, the development of spectroscopy made it possible to more deeply penetrate into the structure of atoms and approach the resolution of such questions of modern chemistry as the nature of chemical affinity, catalysis, the transformation of elements, the structure of high-molecular compounds, etc. (the works of Bohr, Langmuir, Rutherford, Debye, Planck, Kossel, Aston, Lewis, Taylor, Staudinger, etc.). The role of chemistry in tsarist Russia was very modest. Indeed, in the field of theoretical chemistry, individual Russian scientists occupied a prominent place (Lomonosov, Zinin, Butlerov, Mendeleev, Markovnikov, etc.), but in the development of the chemical industry, Russia occupied one of the last places. Only after the October Revolution was the problem of the chemicalization of the entire economy of the USSR posed in its full breadth. By the beginning of the second five-year plan, the basic chemical and fertilizer industry had been strengthened, coke-chemical production had been expanded and reconstructed. Industries of aniline and lacquer-paint, artificial fiber, plastics, rubber, pharmaceutical, etc. were created. Chemical combines are growing: Berezniki, Bobriki, Khibiny. The network of scientific research institutes, laboratories, departments has been immeasurably expanded. The most important chemical laboratories and institutes in the USSR are: laboratories of the chemical and biological associations of the Academy of Sciences of the USSR, the N. D. Zelinsky Institute of Organic Chemistry, the Karpov Physicochemical Institute, the State Institute of Applied Chemistry, the Chemical-Pharmaceutical Institute, the Institute of Organic Intermediates and Dyes, the chemical sector of the VIEM, and laboratories of departments of higher educational institutions (laboratories of chemistry at Moscow State University, the Military Chemical Academy, Leningrad University, Kazan University, etc.). All this contributes to the growth of the chemical power of the Union and its advancement in the chemical industry to one of the first places, and along with this, the growth of chemical scientific forces and chemistry itself. To exchange experience and jointly discuss their work, chemists unite into chemical societies (the Mendeleev Chemical Society in the USSR, the Deutsche chemische Gesellschaft, the Société chimique de France, the American Chemical Society, etc.), international congresses are periodically held (e.g., the Mendeleev congresses held in the USSR), and a number of periodicals are published (such as the Journal of General and Physical Chemistry, the Journal of the Chemical Industry, the Chemical-Pharmaceutical Journal in the USSR, Berichte der deutschen chemischen Gesellschaft, Zeitschrift für analytische Chemie, Zeitschrift für physikalische Chemie, Zeitschrift für anorganische und allgemeine Chemie, Mikrochemie, Kolloid-Zeitschrift in Germany, the Journal of the American Chemical Society in America, the Journal of the Chemical Society in England, Bulletin de la Société chimique, Annales de chimie in France, etc.). The teaching of chemistry in medical educational institutions pursues two goals: 1) to provide a stock of chemical knowledge, thanks to which a physician can consciously understand the chemical processes occurring in a healthy and diseased organism, compare them with the picture obtained during clinical examination of blood, urine, feces, etc., orient themselves in pharmacology, chemotherapy, understand the causes of occupational diseases and carry out preventive work in chemical industries; 2) to teach the student to draw conclusions and comparisons from the experimental material with which he becomes acquainted in practical exercises, and to expand the general cultural horizons of the student. Since individual chemical disciplines are in a genetic connection with each other, it is advisable to teach chemistry in the following sequence: inorganic chemistry, analytical chemistry, organic chemistry, physical chemistry, colloid chemistry, and biological chemistry.