PLATINUM METALS (synonym platinoids) — chemical elements of the 5th and 6th periods VIII In Mendeleyev's groups. To P. the m possess light metals ruthenium (see), rhodium (Rhodium, Rh), palladium (see) and heavy metals osmium (Osmium, Os), iridium (see) and platinum (Platinum, Pt). The item of m and their alloys are used in stomatology, in prosthetics, at production of electrodes, including the electrodes implanted in a brain and other tissues of experimental animals in experiments on studying of century of N of, in regulation of processes of a metabolism it. the item, at production of chemical ware and the equipment, separate details of devices, etc. Osmium tetroxide (osmium tetroxide; 0s04) it is used in a histochemistry. Serve as catalysts of many chemical reactions in a melkorazdroblenny condition of P. of m and for this purpose are widely applied in the chemical industry. Connections P. of m have toxic properties and can represent professional harm for the people having with them contact in a process of manufacture.
In P.'s nature of m meet seldom and in small amounts. Reliable data about their contents in a human body are absent. Get P. of m from scatterings and during the processing of nickel copper ores.
In total P. m have color, silver-white with a metal brilliant shade, and are characterized by high chemical inertness. Only palladium is oxidized nitric to - that, passing into Pd nitrate (NO 3 ) 2 . Platinum is oxidized aqua regia (mix salt and nitric to - t) during the heating, forming chloroplatinic to - that. M turn other P. into soluble compounds during the heating in fusion of alkali and any oxidizer (Na 2 O 2 , KNO 3 etc.). Double (binary) chemical connections P. of m with oxygen, halogens and some other nonmetals are known. However education is most characteristic of P. of m complex connections (see). (I.e. the atoms or groups of atoms connected with the central atoms P. of m) in these connections simple ions of halogens and oxygen and difficult ions and molecules can be ligands. The strongest complex connections with P. of m form amino acids, proteins, nitrogen bases and polynucleotides of bioorganic monomers and polymers. Nek-ry physical. - the chemical data characterizing P. by m are provided in the table.
In the 70th 20 century data on antineoplastic activity of some compounds of platinum appeared. For the first time these properties at cis-dichloro - diaminoplatinum (II) — [Pt (NH 3 ) 2 Cl 2 ], in abbreviated form DDP, were open in 1969 by Rosenberg (V. for Rosenberg). On primary trial it was put St. 1000 various complex connections P. of m and more than 20 compounds of platinum, perspective concerning their use in chemotherapy of patients with malignant new growths are selected. On structure the majority of these substances (nonelectrolytes, cis-the isomers derivative of bivalent platinum) is similar to DDP. So far DDP remains the most effective connection. This active substance in the chemical relation, in Krom ions of Cl - are partially replaced with water molecules with formation of an ion [Pt (NH 3 ) 2 (H 2 O) 2 ] 2+ . Process of ionization of DDP goes hl. obr. in cells where concentration of chlorides is lower, than in blood serum. The hydrolysate of DDP reacts with the DNA nitrogen bases as the bifunctional agent, causing cross-linking action between DNA threads. It serves as the main reason for disturbance of division and death of tumor cells. The additional mechanism of antineoplastic action of DDP is activation of system of immunity of an organism. However in addition to action on cells of malignant new growths of DDP has toxic effect on normally functioning cells of a number of bodies and systems. Causes in experimental animal DDP injury of a mucous membrane of a small bowel, gyrose tubules of kidneys, changes in bodies of a hemopoiesis. At small doses of DDP these phenomena have reversible character. Action of DDP on kidneys represents the major factor forcing to interrupt treatment of patients with this drug. Out of an organism of DDP it is brought preferential with urine (60 — 70% of the entered quantity are removed in the first days). The greatest number of drug is found in went. - kish. path, kidneys and liver. DDP is capable to overcome the acquired other chemotherapeutic drugs resistance of tumors that is one of basic features of this complex compound of platinum. Drug is used still restrictedly in a combination with other chemotherapeutic means. It is most effective at treatment of patients with tumors of a small egg, a bladder, ovaries, area of the head and a neck.
Connections P. of m in a varying degree have toxic properties. Flying Ru04 and 0s04 tetroxides, especially the last, easily formed at oxidation of compounds of osmium are substances most dangerous in this respect. Low concentrations 0s04t in air cause eye pain, conjunctivitis, irritation of a mucous membrane of upper respiratory tracts. More intensive influence causes the damage to a cornea leading to a blindness, bronchitis, pneumonia, a digestive disturbance. Inhalation within half an hour of air, concentration 0s04 in Krom makes 0,001 mg/l, passes without effects, however there is an opinion that presence of vapors 0s04 at air of workrooms in general is inadmissible.
In industrial, and sometimes and in vitro compounds of platinum can get to air in the form of an aerosol or vapors and to render irritant action on skin, mucous membranes and a respiratory organs. As a result of it the individuals working with connections P. of m have a symptom complex called platinozy (difficulty of breath, cough, sneezing, cold, conjunctivitis, urticaria). The disease begins in several weeks or months after the beginning of contact with compounds of platinum and further becomes aggravated. Its symptoms can disappear and appear temporarily again at repeated contacts with P. of m. At long contact with compounds of platinum asthma and eczema can develop. Sensitivity is usually shown to any P.'s connections by m, but in 30% of cases selective sensitivity to compounds of platinum is observed. At long impact of these connections on an organism there can be a sensitivity to other allergens. Believe what most often platinoz causes hexachlorine-platinate (IV) of ammonium.
At emergence of symptoms platino-for it is necessary to stop contact with P. of m; symptomatic treatment.
Measures of the prevention and protection against poisonings with toxic connections P. of m are sealing of the industrial and laboratory equipment, local ventilation, overalls, protection of skin of hands, eyes and a respiratory organs from direct contact with aerosols, couples or solutions of connections P. of m. Vessels with 0s04 shall be densely corked and be stored under draft.
Maximum allowable concentration for soluble compounds of platinum is equal in air of production rooms to 0,002 mg/m3.
Table. SOME PHYSICAL AND CHEMICAL CHARACTERISTICS of PLATINUM METALS
Bibliography: Harmful substances in the industry, under the editorship of N. V. Lazarev and I. D. Gadaskina, t. 3, page 555, L., 1977; Village of Livingston. Chemistry of ruthenium, rhodium, palladium, osmium, iridium, platinum, the lane with English, M., 1978; P r e of dreams of M. A., Konovalov A. L. and Korolchuk V. P. Complex compounds of platinum in chemotherapy of malignant tumors, Vestn. USSR Academy of Medical Sciences, No. 2, page 68, 1979; Cleare M. J. Transition metal complexes in cancer chemotherapy, Coordinat. Chem. Rev., v. 12, p. 349, 1974.
A. V. Babkov.