Reagents

REAGENTS, individual chemical substances or mixtures used in laboratories to carry out chemical reactions in a pure form, without side processes that obscure or distort the given reaction. The necessity of carrying out chemical reactions in a pure form is most clearly expressed in the practice of chemical analysis; therefore, the word "reagents" usually primarily implies analytical R. and indicators. However, reactions in a pure form are necessary not only in analysis but also in each detailed study under laboratory conditions of any chemical process, phenomenon, method, etc. This concept of R. is thus extremely broadened, and from this point of view, all known elements and compounds in chemistry can be classified as R. In practice, however, the range of laboratory preparations considered as R. and constantly manufactured by reagent factories is limited by the size and constancy of demand. Primarily, it includes substances used in various chemical practical courses in higher and secondary schools, and then the most characteristic representatives of various classes and types of chemical compounds most frequently used in chemical research. The noted indefiniteness of the concept of R., increasing as the number of studied compounds grows, has led reagent firms to divide the assortment produced in catalogs into R. for analytical purposes and R. for scientific purposes. The development of analytical chemistry in the direction of replacing classical methods of analysis with new ones based on the use of specific organic R. continuously increases the division of analytical reagents. Along with these two categories, several categories of preparations used not for carrying out reactions but for fixing and verifying the physical properties of substances or for calibrating measuring instruments are also included in the group of laboratory preparations united under the general concept "reagents." Examples of such preparations can be liquids with a precisely established high specific gravity used for rapid determination of the specific gravity of ores and rocks. This also includes substances with constant and precisely verified heat of combustion, used for determining the constants of calorimeters; substances with a specific refractive index for calibration and verification of refractometers, solvents for determining molecular weights, etc. At the present time, such preparations as normal metals used as reference points for high-temperature measuring instruments, or purest gases and organic liquids with precisely established freezing points must also be included among such preparations. All these preparations can be united under the general name physicochemical R. A special group of R. consists of preparations specially intended for microbiological work. This includes stains for microscopy, fixing liquids and mixtures, some nutrient media, characteristic substances in chemically pure form used for identification of microorganisms, etc. Thus we have four groups of laboratory preparations united under the general term "reagents": 1) proper analytical R., 2) R. for scientific work, 3) physicochemical R. and 4) R. (and stains) for bacteriology and microscopy. The systematic manufacture of R. as a special branch of chemical production began to develop in the 1860s. Almost simultaneously, Merck in the laboratory at his pharmacy in Darmstadt and Kahlbaum at the alcohol factory in Adlershof near Berlin began to manufacture pure preparations for laboratory needs. The further development of the reagent business coincided with the flourishing of the German chemical industry, and by the beginning of the 20th century, Germany became almost the monopolistic supplier of R. for laboratories worldwide, which it remained until the beginning of the imperialist war. During the war, R. production was organized in other countries as well. One of the most complex issues in the reagent business is the question of the quality of R. and their proper qualification designation. In the early periods of the development of the reagent business, the quality of R. was usually determined in accordance with the requirements of the pharmacopoeia; however, as the assortment of R. and their specialization developed, it became necessary to develop special methods for their testing. One of the first to compile a preparation and testing guide for 75 of the most important analytical R. was Fresenius in his classic guide to analytical chemistry. Then in 1888, a book by Krauch "Testing of Reagents for Purity" was published in Germany. In the nineties (and in a second edition in 1902), the Russian book by A. Korenblit "Chemical Reagents, Their Preparation and Testing" was published. In 1905, the firm Merck published the book "Testing of Reagents for Purity," subsequently reissued in 1912 and 1922. All the aforementioned "Tests" are exclusively qualitative in nature and do not provide information about the quantities of impurities remaining in R.; in addition, they lack indications of the qualification divisions of R. according to their degree of purity. Based on these guides, as well as their own analytical archives and experience, reagent firms issued their preparations with the most varied qualification designations: chemically pure, for analysis, purest, pure, etc. Some firms issued the most valuable preparations with indication on the labels of the quantities of the most important impurities contained in them, however these figures could only have approximate value, as there was no data on the methods by which these figures were obtained. The indefiniteness of the question of the universally obligatory quality of R. became especially noticeable after the war, when the production of reagents began to develop in different countries, and consumer laboratories ceased to base their trust in R. on the authority of the supplying firm. Individual firms and scientific societies were forced to engage in the thorough development of methods for testing R., based on the precise fixing of permissible quantities of impurities. The first to take this path was Murray in his book "Standards and Testing of Reagents," published in 1920 in America and reissued in 1927. Then between 1923 and 1930, the question of standardization of R. was dealt with by a special commission of the International Bureau for Standardization of Reagents of the American Chemical Society, which has published over a hundred standards to this day. During the same period, the firm de Haan (Germany) began to issue guaranteed R. according to a catalog in which not only the permissible quantities of impurities but also the methods for their determination, developed by the school of Prof. Bottger in Leipzig, are indicated. In the USSR, the Reagent Institute has been working on the standardization of R. since 1927, based on the division of R. into three qualifications according to purity: "chemically pure," "pure for analysis" and "pure." For each qualification, the permissible quantities of impurities are fixed, verified, and methods for their determination are given. "Chemically pure" R. are preparations of the highest achievable degree of purity in serial production. The permissible quantities of impurities usually stand at the limit of sensitivity of modern analytical methods. Such R. are intended for analytical work of exceptional accuracy (primarily for the analysis of the reagents themselves) and for physicochemical research. "Pure for analysis" preparations are the normal R. for all precise analytical determinations. The content of impurities in them corresponds on average to the standards of Merck, Murray, and American standards, i.e., in quality they correspond to the best foreign R. "Pure" are preparations for less critical quantitative determinations, for educational purposes, for synthesis needs, or preparations for special purposes in which noticeable quantities of some impurities do not hinder their application. As of November 1, 1932, standards have been developed for 104 reagents, of which 90 have been approved by the STO Committee. In pre-revolutionary Russia, there was absolutely no production of R. The educational and few industrial laboratories of the country used R. exclusively of German origin. During the war, laboratories worked mainly on the remnants of reagents from previous stocks and on pharmaceutical salts. The pioneers of reagent production in the USSR were the cooperative association Kooperakhimia (since 1917) and the Reagent Institute of the VSNKh (since 1919). Since 1927, R. began to be produced by the Chemical Trust (now the Rare Metals Association), and the work on R. of the chemical-pharmaceutical plants of Gosmedtorgprom (Vokhimpharma) was intensified. Subsequently, the Rare Metals Association specialized mainly in the production of R. from rare elements (preparations of molybdenum, vanadium, tungsten, lithium, cobalt, etc.), and the main production of R. is concentrated in the plants of Vokhimpharma, mainly in Moscow. Along with them, a number of local organizations prepare R. in laboratory conditions (Kiev experimental laboratory, Odessa reagent laboratory, etc.); the production of these manufacturers is negligible in comparison with the centralized production of Vokhimpharma plants. The following table shows the growth of general reagent production in the USSR: | Indicators 1921- | 1925- 1925 g. ! 1926 g. 1926- 1927 g. 1927- 1928 G. 1928- 1929 G. 1929-30 g. and a special quarter of 1931g. i Quantity in thousands kg . .

The number of names.... 9(5 100 178 229 ' 205 254 377 294 512 366 1035 390 868 4Ь7 ! Import ! Quantity in thousands of kg.... i 29 369 81 4U no data Approximate data on the USSR's need for R. for 1932: 1,750 thousand kg in 900 names. The plans of Vokhimpharma for the second five-year period provide for the possibility of covering the increasing need of laboratories for R. with domestic production only by 1936. The scales of production and needs given above refer only to R. of laboratory significance. However, many R. are also used directly in technology, and technology imposes on their purity completely the same, and often even higher, requirements than laboratory practice. Such mass application of the purest preparations for technical purposes with the development and complication of technology continuously increases. The supply of R. in the USSR is carried out by Goslabreactivsbyt and its local branches; medical institutions are supplied mainly through health departments and pharmacy administrations along with drug supply. A catalog of R. was published in 1926, its nomenclature and prices are outdated.