PHYSICAL CHEMISTRY

From Big Medical Encyclopedia

PHYSICAL CHEMISTRY — the section of chemistry devoted to studying of interrelation of the chemical and physical phenomena in the nature. Provisions and methods F. x. methods F are important for medicine and medicobiological sciences. x. are used for studying of vital processes as is normal, and at pathology.

Main objects of studying F. x. are a structure of atoms (see. And volume) and molecules (see the Molecule), the nature of chemical bonds, chemical balance (see a chemical equilibrium) and kinetics (see Kinetics chemical, Kinetics of biological processes), a catalysis (see), a gas theory (see), liquids and solutions (see), structure and chemical properties of crystals (see) and polymers (see. High-molecular compounds), thermodynamics (see) and heat effects of chemical reactions (see Thermochemistry), the superficial phenomena (see Detergents, Surface intention, Wetting), properties of solutions of electrolytes (see), electrode processes (see Electrodes) and the electromotive forces, metallic corrosion, photochemical and radiation processes (see. Photochemical reactions, Electromagnetic radiation). Majority of theories F. x. is based on laws of a statics, quantum (wave) mechanics and thermodynamics. During the studying of the put problems in F. x. widely apply various combinations of experimental methods of physics and chemistry, so-called physical. - chemical methods of the analysis, a basis to-rykh were developed in 1900 — 1915.

Use of effect of Messbaue-r (a nuclear gamma resonance), radiospectroscopy (see Spectroscopy), a spektrofotometriya concern to the most widespread fi-ziko-himicheskikhm to methods of the second half of 20 century an electronic paramagnetic resonance (see), nuclear magnetic resonance (see), mass spectrometry (see), (see) and a flyuorimetriya (see), the X-ray crystallographic analysis (see), a submicroscopy (see), an ulypratsentrifu-girovaniye (see), gas and solution chromatography (see), an electrophoresis (see), isoelectric focusing (see), a polyarografiya (see), a potentsiometriya (see. Electrometric it is titrated iye), a conductometry (see), an osmometriya (see. Osmotic pressure), ebull an ometriya (see) etc.

The term «physical chemistry» for the first time appeared in works it. the alchemist Kunrat (H. Kuhnrath, 1599), however long time the sense put in this term did not correspond to its true value. Tasks F. x., close to their modern understanding, M. V. Lomonosov for the first time formulated «Introduction to true physical chemistry», read to them in 1752 to students of the St. Petersburg akadekhmiya of sciences is aware: the physical chemistry, according to M. V. Lomonosov, is the science explaining on the basis of provisions and experiences of physics what occurs in the mixed bodies at chemical reactions. Systematic teaching F. x. it was begun since 1860 in Kharkiv un-those H. N. Beketov, to-ry for the first time on natural f-those it un-that organized physical and chemical department. After Kharkiv un-volume teaching F. x. it was entered in Kazan (1874), Yuryevsky (1880) and the Moscow (1886) high fur boots. Since 1869 the magazine of Russian physical and chemical begins to appear about-va. Abroad the department of physical chemistry was for the first time founded in Leipzig in 1887.

Formation F. x. as independent scientific discipline it is connected with atomic theory, i.e. first of all with opening in 1748 — 1756 by M. V. Lomonosov and in 1770 — 1774 A. Lavoisier of conservation law of mass of substances at chemical reactions. Richter's works (J. Century of Richter, 1791 — 1802), opened the law of shares (equivalents), Proust (J. L. Proust, 1808) who opened the law of definite proportions, etc. promoted creation in 1802 — 1810 by J. Dalton to the atomic theory and opening of the law of multiple proportions determining consistent patterns of formation of chemical connections. In 1811 A. Avogadro entered the concept «molecule» connecting the atomic theory of a structure of substance with laws of ideal gases. Logical conclusion of formation of atomistic views of the nature of matter was opening by D. I. Mendeleyev in 1869 of the periodic law of chemical elements (see the Periodic Table).

Modern idea of an atomic structure developed at the beginning of

20 century. The most important milestones on this way are experimental opening of an electron and establishment of its charge, creation of the quantum theory (see) Planck (M. Plank) in 1900, Bohr's works (N. Bohr, 1913) who assumed existence at atom of an electron shell and created its planetary model, and other researches which served as confirmation of the quantum theory of an atomic structure. The final stage of formation of modern ideas of an atomic structure was development of quantum (wave) mechanics, by means of methods the cut in the subsequent was succeeded to explain the nature and an orientation of chemical bonds, to theoretically calculate physical. - chemical constants of the elementary molecules to develop the theory of intermolecular forces, etc.

Initial development of the chemical thermodynamics studying laws of interconversions of various forms of energy in equilibrium systems is connected with S. Carnot's researches in 1824. Further works of R. Mayer, J. Joule and G. Helmholtz led to opening of the law of energy conservation — the so-called first beginning, or the first law of thermodynamics. Introduction by Klauzius (R. Clausius) in 1865 of the concept «entropy» as a measure of free energy, led to development of the second law of thermodynamics. The third fundamental law of thermodynamics was output from the thermal theorem of Nernst of asymptotic rapprochement of free energy and heat content of system, in 1907 A. Einstein worked out the equation of heat capacity of simple harmonious oscillators, and in

1911 Planck drew a conclusion: entropy of pure substances at absolute zero is equal to zero.

The beginning to independent existence of thermochemistry — sciences about heat effects of chemical reactions, was necessary works of G. I. Hess who established the law of constancy of the sums of warmth in 1840. Bertlo's works were of great importance for development of thermochemistry (R. E. M of Berthelot), to-ry developed calorimetric methods of the analysis (see the Calorimetry) and opened the principle of the maximum work. In 1859 H. Kirch-hoff formulated the law connecting heat effect of reaction with heat capacities of reactants and reaction products. In

1909 — 1912 of W. H. Nernst, Einstein and P. Debye developed the theory of quantum heat capacity.

Development of the electrochemistry which is engaged izucheniyekhm bonds between the chemical and electric phenomena and a research of action of electric current on various substances in solutions is connected with creation by A. Volta in 1792 — 1794 of a galvanic cell. In 1800 there were first works of V. Nicolson and Karleyl (And. Kag-leil) on decomposition of water, and in 1803 — 1807 of work of I. Bertselius and W. Hisinger about electrolysis (see) solutions of salts. In 1833 — 1834 Faraday (M. of Faraday) formulated the fundamental laws of electrolysis connecting an exit of electrochemical reactions with amount of electricity and chemical equivalents of substances. In 1853 — 1859 J. W. Hittorf established dependence between electrochemical action and ionic mobility, and in 1879 F. W. Kohlrausch opened the law of the independent movement of ions (see) also established connection between equivalent conductivity and mobility of cations and anions. In 1875 — 1878 Gibbs (J. VV. Gibbs) and in 1882 Helmholtz developed the mathematical model connecting the electromotive force of a galvanic cell with an internal energy of chemical reactions. In 1879 Helmholtz created the doctrine about a double electric layer. In 1930 — 1932 Folmer (M. of Vol-mer) and A. N. Frumkin offered the quantitative theory of electrode processes.

The foundation was laid for the doctrine about solutions by Gassenfratts's works (J. H. Hassenfratz, 1798) and Ge. Gay-Lussac (1819) about solubility of salts. In 1881 — 1884 D. P. Konovalov laid the scientific foundation of the theory and practice of distillation of solutions, and in 1882 Raul (F. M of Raoult) opened the law of fall of temperature of freezing of solutions (see Kriometriya). The first quantitative measurements of osmotic pressure (see) were performed in 1877 by W. F. Ph. Pfeffer, and in 1887 Ja. Vant Hoff created the thermodynamic theory of the diluted solutions and removed the equation connecting osmotic pressure with concentration of solution, its volume and absolute temperature. S. Arrhenius in 1887 formulated the theory of electrolytic dissociation and ionization of salts in solutions (see Electrolytes), and Nernst in 1888 — the osmotic theory. W. Ostwald found the patterns connecting extent of dissociation of electrolyte with its concentration. In 1911 Mr. Donnan (F. G. Don-fathers) created the theory of distribution of electrolytes on both sides of a semipermeable membrane (see. Membrane equilibrium), edge found broad application in biophysical chemistry (see) and colloid chemistry (see). In 1923 Debye and E. Huckel developed the statistical theory of strong electrolytes.

Development of the doctrine about kinetics of chemical reactions, balance and a catalysis began with works of L. Wil-helmy who created the first quantitative theory of chemical reactions in 1850 and A. W. Williamson who presented balance as a condition of equality of speeds of direct and return reactions. The concept «catalysis» was entered into a physical hikhmiya by I. Bertselius in

1835. Philosophy of the doctrine

about chemical balance were formulated in Bertholet's works (Page L. Veg-thollet). The foundation of the dynamic theory of balances is laid by A. W. Williamson and Klauzius's works, the principle of mobile equilibrium is developed by Ya. V ant-Goffy, Gibbs and Le Sha H. Le Chatelier. Bertlo and Pean - st L. Pean-saint-Gilles established connection between the speed of response and balanced state. The fundamental law of chemical kinetics about proportionality of speed of response to the work of active masses (i.e. concentration) reactants — the mass action law — was formulated in 1864 — 1867 by Guldberg (S. M. Guldberg) and P. Waage. In 1893 — 1897 A. N. Bach and Engler (To. Engler) created the peroxide theory of slow oxidation (see Peroxides), in 1899 — 1904 of R. Abegg and H. Bodlander developed idea of valency as abilities of atom to accept or give electrons, in 1913 — 1914 L. V. Pisar-zhevsky and S. V. Dine developed the electronic theory of redoxreactions (see). In 1903 — 1905 N. A. Shilov offered the theory of coupled reactions, and in 1913 Mr. Bodenstein (M. Waugh-denstein) opened chain reactions (see), theoretical bases of course to-rykh were developed in 1926 — 1932 of H. N. Semenov and Hinshelvud (Page N. Hinsheiwood).

The phenomenon of radioactive decay of atoms (radioactivity) was open in 1896. A. Bekkerel. Since then (see) much attention is paid to studying of radioactivity and in this area significant progress is achieved, since artificial splitting of atoms and finishing developments on the managed thermonuclear fusion. Among problems F. x. it is necessary to allocate studying of influence on molecules of gamma radiations (see), a particle flux of high energy (see the Alpha radiation, Yass-michesky radiation, Neutron emission, Lrotonny radiation), laser radiation (see the Laser), and also studying of reactions in electric discharges and low-temperature plasma (plasma chemistry). Successfully physical develops. - the chemical mechanic, investigating influence of the superficial phenomena on properties of solids.

One of sections F. x. — the photochemistry (see), studies the reactions proceeding at absorption by substance of light energy from an external source of radiation.

V F. x. there is no such section, to-ry would not matter for a medico-biol. disciplines and eventually for applied medicine (see. Biophysical chemistry). Physical. - chemical methods allow to study living cell and in vivo fabrics, without subjecting them to destruction. For medicine physical have not smaller value. - chemical theories and representation. So, the doctrine about osmotic properties of solutions was extremely essential to understanding of water exchange (see the Water salt metabolism) at the person normal and at pathology. Creation of the theory of electrolytic dissociation significantly influenced idea of the bioelectric phenomena (see) and laid the foundation for the ionic theory of excitement (see) and braking (see). The theory of acids, and the bases (see) gave the chance to explain constancy of internal environment of an organism and formed a basis for studying of acid-base equilibrium (see). For understanding of power of vital processes (e.g., functioning of ATP) the researches conducted by means of methods of chemical thermodynamics widely use. Development physical. - chemical ideas of superficial processes (surface intention, wetting, etc.) it is essential to understanding of reactions of cellular immunity (see), a rasplastyvaniye of cells on noncellular surfaces, adhesions, etc. The theory and methods of chemical kinetics are a basis for studying of kinetics of biological, first of all enzymatic, processes. A big role in understanding of essence biol. processes plays studying of a bioluminescence, hemolyuminestsention (see Biokhemilyuminestsention), use of the luminescing antibodies (see the Immunofluorescence), flyuo-r okhr ohms (see), etc. for studying of properties of fabric and subcellular localization of proteins, nucleinic to - t, etc. Physical. - chemical methods of definition of basal metabolic rate (see) are extremely important during the diagnosing of many diseases, including endocrine.

It should be noted that studying physical. - chemical properties biol. the systems and processes proceeding in a live organism gives the chance to glance more deeply in an essence and to reveal specifics of living matter and these phenomena.

The main research centers in the field of physical chemistry in the USSR are research in-you are Academy of Sciences of the USSR, its branches and departments, AN of federal republics: Physical and chemical in-t of L. Ya. Karpov, Ying t of physical chemistry, Ying t of chemical physics, Ying t of new chemical problems, Ying t of organic and physical chemistry of A. E. Arbuzov, Ying t of a catalysis, Ying t of chemical kinetics and burning, Ying t of physical chemistry of AN of USSR, etc., and also the relevant departments in high fur boots.

The main publications which are systematically publishing articles on F. x., are: «Magazine of physical chemistry», «Kinetics and catalysis», «Magazine of structural chemistry», «Radiochemistry», Elektrokhimiya. Abroad articles on F. x. are printed in «Zeitschrift fiir physi-kalische Chemie», «Journal of Physical Chemistry», «Journal de chimie physique et de physico-chimie bio-logique».

Bibliography: Babko A. K., etc.

Physical and chemical methods of the analysis, M., 1968; Kireev V. A. Course of physical chemistry, M., 1975;

Melvin-Hughes E. A. Physical chemistry, the lane with English, t. 1 — 2, M., 1962; Nikolaev L. A. Physical chemistry, M., 1972; Development

of physical chemistry in the USSR, under the editorship of Ya. I. Gerasimov, M., 1967; Solo

vyev Yu. I. Sketches on stories of physical chemistry, M., 1964; Physical

chemistry, Modern problems, under the editorship of. I. M. Kolotyrkina, M., 1980.

Periodicals — the Magazine of structural chemistry, M., since 1960; The Magazine of physical chemistry, M., since 1930; Kinetics and a catalysis, M., since 1960; Radiochemistry, M. — L., since 1959; Electrochemistry, M., since 1965; Journal de chimie physique et de physico-chimie biologique, P., since 1903; Journal of Physical Chemistry, Baltimore, since 1896; Zeitschrift fiir physikalische Chemie, Lpz., since 1887.

V. A. Pekkel.

Яндекс.Метрика