ELECTROLYTES

From Big Medical Encyclopedia

ELECTROLYTES — substances, conductivity to-rykh in the firm, melted or dissolved state partially or it is completely caused by transfer positively and negatively charged ions — cations and anions. AA. are indispensable components of all vegetable and animal organisms where they participate in functioning of the majority of the vital systems. AA. create membrane potentials (see. Bioelectric potential ), provide carrying out nervous impulse (see. Nervous impulse ), conductivity of biological systems (see), is maintained turgor (see) cells, etc. Set of processes of receipt in an organism of water and AA., their distributions in internal environment and removal from an organism are defined by a condition of a water salt metabolism (see) and acid-base equilibrium (see), and also the volume and qualitative composition of liquids of an organism. Concentration separate E. in blood serum, urine and others biol. liquids is important diagnostic test at a number of diseases of cardiovascular system, endocrine diseases, diseases of kidneys, etc. Deficit E. at a diabetes mellitus (see. diabetes mellitus ) and not diabetes mellitus (see Diabetes not sugar), the nefropatiya which are followed by a polyuria, insufficiency of bark of adrenal glands, profuse ponosa, pernicious vomiting, prolonged use of salurichesky diuretics, hypersecretion of parathormone (see), a hypervitaminosis of D (see Calciferols), etc. leads to the heavy disturbances of a water salt metabolism which are followed by a severe headache and spasms; in hard cases at deficit E. the collapse can develop (see). Surplus E. at disturbance of secretory function of kidneys, dehydration of an organism and at other morbid conditions leads to an angidremiya (see), hyperpotassemias (see), hypercalcemias (see).

Low-molecular salts (see), acids and the bases (see), high-molecular compounds (polyelectrolytes) supporting multiple ionogenic groups — proteins (see), nucleic acids (see), hyaluronic acids (see), polyglutaminic to - you belong to the electrolytes which are breaking up to ions (see) in solutions (see) (see. Glutamic acid ), phosphatides (see) and the substances at dissolution giving colloid solutions (see Colloids) — soaps (see), detergents (see).

Firm E. the substances forming ionic crystals (see) are generally. Ionic conduction nek-ry crystals of other nature, and also amorphous bodies — ion-exchange resins have (see. Ionites ), nek-ry glasses and polymers (see. High-molecular compounds ).

Disintegration E. on ions happens owing to interaction of solute to solvent and is called electrolytic dissociation. If at dissociation from a molecule E. about one cation and anion with equal charges, such E is formed. call symmetric, or binary, and depending on the size of a charge 1 — 1-, 2 — 2-valent etc. If at dissociation of a molecule E. the different number of cations _i anions is formed, e.g. , electrolytes call asymmetrical, 1 — 2-, 1 — 3-valent etc. On number of ions asymmetrical E. subdivide on ternary (3 ions), kvarternarny (4 ions) etc.

In case of incomplete dissociation E. extent of dissociation (a) — the relation of number of the dissociated molecules E. to initial number of not dissociated molecules — determine according to the classical theory of electrolytic dissociation by the equation and = (i-1)/(n-1) where i — so-called coefficient of Vant Hoff, n — number of ions, on to-rye the molecule E dissociates. In infinitely diluted solutions and = ~ 1. The dynamic equilibrium between not dissociated molecules and ions is described by the mass action law (see. The operating masses the law): , where To — a dissociation constant, Joint stock company, Aa, Am — efficiency concentrations of cations, anions and not dissociated molecules respectively. Values and and Kd depend by nature E., solvent and temperature, however size unlike but does not depend on concentration of substance. Communication between and and Kd binary E. it is described by the Ostwald's dilution law and expressed by the equation .

Macromolecules of the polymers containing ionizable group are polyelectrolytes. Distinguish polyacids, the polybases and polymeric ampholytes, to-rye contain both acid, and basic groups (see Ampholytes). In solution a macropier Coolah of polyelectrolyte exists in the form of the polyion surrounded with equivalent number of small antiions. The dissociation constant To weak polyelectrolytes decreases at increase in extent of dissociation and since at the same time the boundary space charge of a polyion increases and for the subsequent dissociation of ions it is necessary to make a lot of work. In the solutions containing low molecular E., the effect of their exception of the areas occupied with a polyion (so-called donnanovsky distribution) is observed.

Extent of dissociation is the important factor defining efficiency fiziol. actions biologically active E., such as alkaloids (see), amines (see), auxins (see), carbonic acid (see), etc. As a rule, the value is higher and, the less these substances are capable to get into cells therefore their physiological and pharmacological effects weaken.

Usually in solutions E. efficiency concentration of ions (activity) is less than their valid concentration, generally because of interaction of ions with molecules dipoles of solvent, i.e. because of solvation (see) and electrostatic interaction of ions among themselves, a cut depends on distance between ions (concentration) and size of their charges (valency). A measure of electrostatic intensity, created by the ions which are in solution, ionic strength (μ) of solution serves, edges is calculated on the equation: , where Z — the valency of ions of this look, With — their concentration, n — number of the ions which are formed at dissociation E. Velichina of activity (A) of electrolyte is defined by concentration (C) and the coefficient of activity (f) depending on a charge and ionic radius, dielectric permeability (see) solvent and temperature and also from concentration (see) substances: And = f*C. In case of the concentrated solutions f depends also by nature E. and solvent. In some cases ions E. thanks to an electrostatic attraction of heteronymic charges associate and form in solution associates — the so-called ion pairs, tees, quadrupoles etc. in general deprived of a charge. At the same time ions can come into direct contact with each other or to be the divided molecules of solvent, i.e. to make the contact or divided by solvent (solvatorazdelenny) ion pairs. Unlike not dissociated molecules ion pairs are not the isolated particles, and are connected with molecules of solvent, i.e. represent very difficult educations. Balance between separate ions and ion pairs is characterized by an association constant or the dissociation similar to Kd. Ion pairs usually arise in solutions asymmetrical E., formed by multiply charged anions and monovalent cations (or on the contrary).

On extent of dissociation E. conditionally divide on weak and strong. Group weak E. includes almost all organic salts, to - you and the bases (see. Organic compounds ), and also the substances forming multiply charged ions. To strong E. carry the substances which are completely dissociating on ions and not forming associates, e.g. mineral salts of alkali metals (see) and alkaline earth metals (see), halogenides, perchlorates and nitrates of nek-ry transition metals.

See also Potassium , Magnesium , Sodium , Carbonic acid , Phosphoric acids , Chlorine .

Bibliography: Bogolyubov V. M. Pathogeny and clinic of water and electrolytic frustration, L., 1968, bibliogr.; Izmaylov N. A. Electrochemistry of solutions, M., 1976; Krokhalev A. A. Water and electrolytic exchange (acute frustration), M., 1972, bibliogr.; Wilkinson A. U. Water and electrolytic exchange in surgery, the lane with English, M., 1974, bibliogr.; Hladik D., etc. Physics of electrolytes: Processes of transfer in solid electrolytes and electrodes, the lane with English, M., 1978.

V. A. Pekkel.

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