REACTANTS CHEMICAL — the substances used in laboratory practice for implementation of various chemical changes. In R.'s medicine x. are used with the analytical and diagnostic purposes in clinical, a dignity. - a gigabyte., biochemical and medical - biol. laboratories. The methods of a research applied and developed in a yole. and a wedge, chemistry, forensic medicine etc., demand the big range of R. x., to-rye shall meet the most various requirements. E.g., for kliniko-biochemical laboratories high cleaning substrates are necessary for enzymes, enzymes, reagents on specific groups (SH-, NH 2 -, COOH-group-y, etc.) etc. For carrying out inorganic and organic sintez, and also in qualitative and quantitative analyses, including at a dignity. - a gigabyte. control in various productions, the analysis of pharmaceuticals, by production of medical analyses, a dignity. - a gigabyte. the analysis of foodstuff, air etc., use a large number of the most various R. x. high extent of cleaning. In most cases R. x. are individual substances, however quite often they have complex structure.
Standard classification of R. x. does not exist. Most often they are divided into analytical R. x. and all others. Analytical R. x. subdivide into standard groups: dissolving (acids and their mixes, alkali, complexing substances, organic solvents, etc.), dividing (the group or specific precipitators extracting substances, complexing substances, etc.); diagnosing (specific — the forming rainfall or the painted products with the analyzed substance or an ion, and also R. x. for preparation of the titrated solutions); auxiliary action, the carrying out necessary applied to creating favorable conditions chemical change (see) — indicators (see), the oxidizers and reducers used for transfer of elements in other valence state, substance for preparation of buffer mixtures, etc.
Value and practical value of analytical R. x. hl depend. obr. from their sensitivity and specificity. R.'s sensitivity x. is defined by sensitivity of analytical reaction, i.e. the smallest quantity or the smallest concentration of that substance (ion), a cut it can be revealed by means of this reactant. River x., serving for detection of this substance (Nona) in the presence of other substances, call specific, however strictly specific R. x. it is not enough since almost always specific R. x. find ability to react with several ions.
One of the main requirements imposed to R. x., their purity is. Extreme impurity level in R. x. it is strictly regulated by the performance specification caused by GOST or technical specifications.
Depending on the content of the main substance and admissible impurity for R. x. the following qualifications are established: «pure» («h»), «pure for the analysis» («chda»), «chemically pure» («hch»). Content of the main substance in reactants of qualification of «h» shall be not less than 98%, «chda» — not less than 99%, «хч» — more than 99%; reactants «хч» contain the smallest amount of impurity (0,001 — 0,00001%). The increased requirements to purity of chemical soyedrsheniye which arose with development of nek-ry new fields of science and technology (radio electronics, production of semiconductors, the analysis of microelements, etc.), caused emergence of production of so-called high-pure substances, for to-rykh two qualifications are established: «standardly pure» («vech») and «especially pure» («ultra high purity»). The corresponding brands are appropriated to high-pure substances, to-rye designate a certain symbol with the number indicating the general content of admissible impurity, and after it — number of the limited impurity and the most admissible summary contents of these impurity. Besides, the large number P. is issued x. required purity and their sets for specific ranges of application: indicators, sets for ultrafiltrations (see), electrophoresis (see), chromatography (see), ion-exchange resins (see. Ionites ), different types of polymers. In research and a wedge, laboratories widely use R. x., marked various isotopes — 14C, 3H, 32P, etc. (see. Isotopes ).
The industry releases special sets P. x. for qualitative and quantitative test of components a yole. liquids of the person in various ways, including by means of autoanalyzers.
Many R. x. over time can change the properties as a result of decomposition, an ovodneniye, oxidation, etc. For the purpose of prevention of the similar phenomena for R.'s most x. certain storage conditions — the low temperature, carefully corked ware from dark glass, storage in exsiccators over water absorbers etc. are necessary. As a rule, R. x., marked isotopes, store at a low temperature (— 20 °), at their use it is necessary to consider time of half-decay of each specific isotope. Strong, explosive or flammable R. x. demand special storage conditions.
Scientific center on development of techniques of preparation and R.'s testing x. in the USSR the all-Union scientific research institute of chemical reactants and osobochisty chemical in-in in Moscow is.
Bibliography: Brudz V. G., Rakovskaya V. A. and Uskova L. E. Reference book of indicators of quality of chemical reactants, book 1 — 2, M., 1968; Modern methods in biochemistry, under the editorship of V. N. Orekhovich, t. 3, M., 1977; The Reference book of the chemist, under the editorship of B. P. Nikolsky, etc., t. 4, M. — L., 1965; F r pi rn of t and D. M t. Reactants and drugs for microscopy, the Reference book, M., 1980; Chemical reactants and drugs, under the editorship of V. I. Kuznetsov, M. — L., 1953.
A. E. Morokhovets.