CHROME (Chromium, Sg) — chemical element VI of group of a periodic system of elements of D. I. Mendeleyev. Chrome and its connections find broad application as oxidizers at organic synthesis, including synthesis of pharmaceuticals, in production of dyes, the textile and tanning industry, at production of a film, in metallurgy, etc. Chrome on the productions connected with use of its connections represents essential professional harm since chrome, its oxides, bikhromatt, etc. have properties to oppress fermental systems of energy fabric balance, to lower immunol. reactivity of an organism. There are data that compounds of chrome possess, besides, mutagen and oncogenous action.
For the first time chrome was emitted in 1797 by L. N. Vauque-lin from mineral of Rsg04 crocoite, and elementary chrome was received by R. W. Bunsen at electrolysis of solution of Sgs12 chromium dichloride. Crust of chrome contains 8,3-10 ~ 3% on weight, however in an elementary state it does not meet. Chromite, or the FeCr204 chromite consisting of iron oxides and chrome is most spread mineral. In vegetable and animal organisms chrome is found only in trace quantities.
Atomic number of chrome 24, atomic weight (weight) 51,996. In an elementary state it represents metal of silver-white color with a bluish shade. Natural chrome consists of four stable isotopes with mass numbers 50 (4,35%), 52 (83.79%), 53 (9,5%) and 54 (2,36%). 8 radioisotopes of chrome with mass numbers 45, 46, 47, 48, 49, 51, 55, 56 are known. Six of them are ultrako-rotkozhivushchy, radioisotopes 48 of Sg and 51 Sg have half-lives 21,56 hours and 27,7 days respectively. The last from them found practical application in medicine.
For a wedge, uses of 51 Sg receive hl. obr. radiation by neutrons in the nuclear reactor of targets from the chrome enriched 50 Sg on reaction of 50 Sg (p, s) 51 Sg, or radiation by protons or deuterons on a cyclotron of a target from natural vanadium with the subsequent allocation from it 51 Sg without carrier. 51 The Sg breaks up by electron capture (100%) with the subsequent emission of characteristic x-ray emission with mean energy apprx. 5 kev. Disintegration of 51 Sg in 9,83% of cases is followed at - radiation (with energy 320 kev), on Krom this radioisotope and detect.
For a wedge, uses b1sg usually release in the form of injection solutions of sodium of chromate and chromium dichloride. The drugs containing 51 Sg use for definition of life expectancy of erythrocytes, leukocytes and thrombocytes, volume of a blood plasma and erythrocytes, volume of the circulating blood, for diagnosis went. - kish. bleedings, and also during the studying of metabolism of chrome in an organism.
Chrome differs in the hardness and refractoriness, its density of 7,19 g/cm3, hardness across Brinnel of 110 — 170 kg! mm2, * °pl 1890 °, g°kip 2680 °, thermal conductivity coefficient of 0,16 kcal! cm • sec. • hail. (20 °), electrical resistivity 12,8 — 14,1 mky» cm (20 °). Chrome possesses is weak ym to an antifa r ro ma gnetizmo m.
Chemically chrome is a little active. Nitric, phosphoric, chloric to - you passivate chrome, i.e. form the oxide film having exclusive anticorrosive properties on metal. At 600 — 700 ° chrome interacts with alkalis, sulfur, hydrogen sulfide, sulfur dioxide, at 800 — 850 ° reacts with phosphorus, ammonia, nitrogen oxide, at 1000 ° is oxidized carbon oxide. In the connections chrome preferential shows valency +2, +3 and +6 (+1, +4, +5 is more rare). Compounds of trivalent chrome are steadiest. Chromium trioxide, or chromic Sg03 anhydride, is very strong oxidizer, apply it to electrodeposited coating (chromizing) of various materials and to receiving sesquioxy - yes Sg203 chrome. At dissolution of Sg03 in water are formed chromic to - you with the general formula p*sg03*n20 where p it is equal to 1 — 4. Chromic to - you exist only in solutions. Salts chromic to - you N2sg04 — the chromates having an appearance of yellow or yellow-orange crystals and salts two-rum to - you N2sg207 — bichromates (bright red crystals) are widely applied in chemical and biochemical laboratories and the industry. Solution of potassium bichromate in the concentrated chamois to - those represents very strong oxidizer used for washing of laboratory glasswares. Sodium bichromate is applied to coagulation of proteins at a dressing (so-called chromic skin), Rsg04 lead chromate — chromic yellow serves as dye, Sg203 — chromic green is an end product of decomposition on air of the majority of compounds of chrome and the steadiest of all its connections, it is used as dye for coloring of glass, ceramics, etc. Paints on a basis of Sg203 are steady against effect of light, fire, oxygen. The powder Sg203 is used as polishing material and the catalyst of process of cracking, etc. For an alloying of staly use ferrochrome — alloy of chrome (apprx. 70%) with iron that gives to steel the increased durability (armor) or firmness against corrosion (stainless steel). Stainless steel is widely used for production of medical tools. Electrolytic deposition of chrome on other metals is widely applied (see Electrolysis). The layer of chrome protects them from corrosion, increases wear resistance and improves outward of metal details. Chrome-plated metals are also material for production of medical tools and devices.
In acid medium ions of Sg3 + can be recovered by strong reducers, napr, zinc, to Sg2 + or [in Sg (H206)]2+. Chromous compounds are extremely unstable and decay on air. Having considerable recovery activity, ions of Sg2 + are capable to recover H+ of water to free hydrogen. From not oxygen compounds of chrome the greatest use hectares a log-nidy, napr have, the Sgs12 chromium dichloride used for chemical sedimentation of chrome (chromizing or cementation of metals chrome), and also carbides, e.g. Sg3s2 surpassing in hardness topaz and quartz, various chromic alum, e.g. KCr(S04)2 — it is lame the potash alum applied in the textile, tanning industry, in production of a film, etc.
All quantitative methods of definition of chrome in solutions are based on its oxidation to Sg20 72 ~ by persulphates, chloric to - that, Kmp04 potassium permanganate, etc. also the subsequent definition of an ion of bichromate photometric or on staining reactions with EDTA or benzidine (see Colorimetry).
Chrome as professional harm. Chrome comes to air of production rooms at galvanization, the soldering, welding, in production of cement, during the burning of nek-ry types of fuel. On productions where chromates are applied, there can be a release of their dust in air of a working zone. During the crushing of chromium ores workers can be affected by a trivalent hrokhm (Sg203), at extraction of chrome from ores — three -
the II hexavalent chromium.
At excess receipt in an organism under production conditions chrome significantly breaks processes biol. oxidations (see biological oxidation). Chrome oppresses tissue respiration and, breaking a cycle tricarboxylic to - t (see Tricarboxylic acids a cycle), leads to suppression of energy balance in cells. Nek-ry researchers consider that compounds of chrome (chromium trioxide, bichromates, etc.) on the action on an organism remind m - and N cholinolytics.
Chrome is capable to accumulate in a human body, it easily gets into lungs and collects in them; at the persons working in contact with chrome, this metal is found in lungs in many years after stoppage with it. Toxic effect of chrome correlates with its valency: with increase in its valency it amplifies. The highest chromium oxides are much more aggressive than the lowest and render more expressed irritant action on a mucous membrane of respiratory tracts and pulmonary fabric.
Compounds of hexavalent chromium possess all-toxic, hepatotoxic and nephrotoxic action, causing specific damage of skin, mucous membrane of a nose and a cartilaginous part of a nasal partition, the pneumosclerosis, an inflammation of bodies went. - kish. path, dystrophic changes of a liver and kidneys. At working at the productions connected with chrome assume existence in bodies and fabrics of «toxic depots» also the possibility of activation of endogenous pro-oncogenes by it is lame (see the Carcinogenesis).
Almost insoluble connections of three - and hexavalent chromium have bigger oncogenous activity io to comparison with its readily soluble connections as in fabrics and liquids of an organism concentration of readily soluble compounds of chrome quickly decreases due to their diffusion. Compounds of hexavalent chromium have mutagen activity more than compounds of trekhvylentny chrome that is aggravated with its property to accumulate in an organism.
At the heart of allergic reactions and the wedge, manifestations of toxic effect of chrome lies its ability to formation of complex connections (see). Hexavalent chromium in skin and internals can be recovered to trivalent and form complex bonds with salts of nitrogen, sulfur, fabric proteins.
Ability to be absorbed and collect in pulmonary fabric and to migrate in bodies of system of mononuclear phagocytes (see) are identical to connections of three - and hexavalent chromium. At parenteral receipt chrome is quickly soaked up in blood, at intake of chrome in its absorption in blood is much lower. Irrespective of a way of receipt in an organism chrome accumulates on a long term in a liver, kidneys, a spleen, bones, marrow and lungs. Removal of chrome from an organism is carried out more through kidneys and to a lesser extent — through intestines. Hexavalent chromium has ability to get through a placental barrier and to collect in fabrics of a fruit, chrome can also come to an organism of the child with breast milk.
Hron. poisoning with chrome and its connections is shown by its local (cauterizing) action on a mucous membrane of airways and skin, and also symptoms of all-toxic action. The contact with compounds of chrome leads to subatrophic changes of a mucous membrane of upper respiratory tracts, is followed by dryness in a nose and a nasopharynx, irritation in a throat, sharp dry cough. Within a year after the beginning of contact with compounds of chrome damage of upper airways can develop from surface erosions of a mucous membrane of nasal sinks and a nasal partition before extensive perforation.
Damage of skin is explained by irritant action of chrome and its connections (so-called chromic burns and ulcers) and their sensibilizing influence (allergic dermatitis and eczemas). Local action of chrome on skin can cause an independent occupational disease or be combined about a wedge, manifestations of all-toxic effect of chrome.
At chromic intoxication digestive organs and respiratory organs preferential are surprised. Develop widespread gastritis (see) with symptoms of endogenous (preferential fundal) and exogenous (preferential antral) gastritis, a peptic ulcer (see) a stomach and a duodenum with a persistent pain syndrome and a tendency to a penetration and perforation of ulcers. Damage of a liver from functional disturbances without subjective symptomatology can pass into so-called chromic hepatitis eventually. Pulmonary pathology at hron. intoxications chrome it is characterized by an intersticial chromic pneumosclerosis (see). Already at early stages of intoxication develop vascular dystonia (see Dystonia vascular) with disorder of regulation of cordial activity (see. Neurocirculatory dystonia), it is preferential with hypotension and bent to bradycardia, asthenic frustration (see. Asthenic syndrome).
Acute poisonings with chrome and its connections meet extremely seldom at very high concentration of dust of potassium bichromate or other compounds of chrome in air of workrooms or hit of large numbers of compounds of chrome inside. At acute poisoning with chrome vomiting, a diarrhea, hemorrhagic diathesis, acute cardiovascular insufficiency are observed. Approximately in 8 days after intake of poison develops in an organism nekronefroz and there occurs defeat of the hemopoietic bodies, note anemia (see), a leukocytosis (see) or a leukopenia (see), cases of pernicious anemia at poisons of l are described en by AI it is lame m.
The first p about m about shch and urgent t e r and p and I. At hit of chrome and its connections on skin an affected area wash out a large amount of water with the subsequent imposing of a bandage with an emulsion hell of a reason. At hit of chrome in eyes immediate and long washing of eyes water, and then an instillation of 30% of solution of Sulfacylum-natrium is necessary (Albucid-natrium). Pharmaceuticals of cholinolytic action (see. Cholinolytic substances) reduce a wedge, displays of chromic intoxication. The most effective drugs in this case are adrenaline, ephedrine, dihydroergotamine, phentolamine, Obsidanum, amizyl. Further treatment — symptomatic.
Examination of t r at d about with p wasps about N about with t and. Questions of examination of working capacity, medical and labor rehabilitation at intoxication chrome and its connections are solved taking into account expressiveness of clinical symptoms of intoxication and the hygienic characteristic of working conditions (see Examination medical labor).
Prevention of poisonings with chrome. In prevention of poisonings with chrome and its connections on productions observance a dignity is of great importance. - a gigabyte. requirements, mechanization of productions, sealing of the equipment, use of local ventilation (see) and increase in its efficiency, use of onboard suctions for bathtubs of chromizing, individual protection equipment on pyleopasny sites of work (see Respirators, P rotivo-gases). Also periodic medical examinations are obligatory preliminary (see. Medical examination), the carried-out with participation of the otorhinolaryngologist and other specialists. The dignity is of great importance systematic. - a gleam, work. The workers connected with production of chrome and its connections receive to lay down. - the prof. food on a special diet with inclusion of a liver, fish, cheese, cottage cheese, green peas, eggs, vegetable dishes, salads, etc. Fat grades of meat, a smoked product, mutton, salty fish are excluded from a diet (see clinical nutrition). Reception of vitamins A, V, S, PP is in addition provided.
Maximum allowable concentrations for chromic anhydride, chromates, bichromates (in terms of Sg03) in air of a working zone of 0,01 mg/m3, for Cr (III) of 1 mg/m3, and in free air for Sg (VI) 0,0015 mg/m3, in water of reservoirs of 0,5 mg/l for Cr (III) and 0,1 mg/l for Cr (VI).
Minimum significant activity of open drugs from 51 Sg in a workplace which is not demanding registration or obtaining permission of bodies of the State sanitary inspection can be equal 100 mkkyur, or 3,7 MBK (on radio toxicity of 51 Sg treats group G).
Bibliography: Harmful substances in the industry, under the editorship of N. V. Lazarev and I. D. Gadaskina, t. 3, page 486, JI., 1977; 3 and with l and D. M. N, T yu sh N I to about in and N. V. and Likhachevaye. I. Klinika of chronic professional intoxication chrome, Gigabyte. work and the prof. having got sick., No. 7, page 26, 1979; L e in and V. I N. Receiving radioisotopes, M., 1972; Pa of hectare and Yu. V. N and To about z and h e N to about V. I. Mutagen activity of compounds of chrome, Gigabyte. and dignity., No. 5, page 46, 1981; Groves and A. V., Ordzhonikidze E. K. N. and P riluts-to and I am L. L. K to a question of destiny of chrome in an organism, the Gigabyte. work and the prof. having got sick., No. 9, page 14, 1982; With and l of l and A. Hr, the lane with English, M., 1958; Tsfasman A. 3. Use of radioactive chrome in clinic, M., 1964; LangardS. Carcinogenic and toxic effects of chromium, Oslo, 1980;
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V. V. Bochkaryov (I am glad.), A. V. Roshchin, E. K. Ordzhonikidze (gigabyte), V. A. Pekkel