SILVER

From Big Medical Encyclopedia

SILVER (Argentum, Ag) — chemical element I of group of a periodic system of D. I. Mendeleyev, belongs to noble metals. In S.'s medicine and its connections use as pharmaceuticals, in stomatology silver amalgam is sealing material (see). In gistol, researches of salt C. apply to impregnation of fabrics and their components metal silver (see. Argirofilnost , Silverings methods ). Nek-ry structural elements of fabrics, napr, argentaffin cells (see), are capable to recover solution of ammoniac NH silver 4 Ag; this their property is also used in histology. Alloys and connections C. and pure S. go for production of a special laboratory glassware sensitive p supersensitive film and films, details of various devices, jewelry. The page serves as the catalyst in an inorganic p organic synthesis. All soluble compounds of S. are toxic.

S.'s maintenance in crust makes 10 - 5  %, in sea water — 0,3 — 10 mg/t. The page is a part of vegetable and animal organisms. S.'s maintenance in plants depends on its concentration in the soil; tissues of mammals and the person contain about 0,03 mg of S. on 100 g of dry weight. The daily diet of the person contains about 0,08 mg of silver. In S.'s nature meets in the form of native silver impurity of other elements, with to-rymi it forms firm solutions (see), and also in the form of connections as a part of various minerals.

Sequence number of silver 47, atomic weight (weight) 107,87. Natural S. consists of two stable isotopes with mass numbers 107 (51,35%) and 109 (48,65%). Also 14 radioisotopes C. (with mass numbers from 102 to 117) and 10 isomers with half-lives from several seconds to several years are known (see. Isomerism , Isotopes ).

Practical application as radiotracers in chemistry, metallurgy and biology was found by the radioisotopes of Page 110mAg and 111Ag received by radiation by neutrons of silver or palladic targets in the nuclear reactor (half-lives of these isotopes are equal respectively 253 days and 7,43 days). Earlier uomAg isomer was used in medical radiology in the form of a radioactive colloid, however now its serial release is stopped in connection with emergence of more effective radio pharmaceuticals (see), received, in particular, on the basis of radionuclides of yttrium ( 90 Y), technetium ( 99m CU), indium ( 113m In), etc.

S. represents metal of white color; its density at the room temperature of 10,50 g/cm 3 , t°pl 960,5 °, t°kip 2212 °. Chemically S. maloaktivno, but forms alloys with many metals. In connections C. usually odnovalentno though connections of two - and trivalent silver are known. In usual conditions of S. does not connect to oxygen, connects to hydrogen sulfide C. easily, forming AgS sulfide, water-insoluble. With halogens C. easily reacts at a usual temperature, and with sulfur — at high. Under the influence of light halogenides C. decay on the making elements (see. Photochemical reactions ); the photo is based on this reaction. In salt to - those and in alkalis C. it is not dissolved, and in nitric to - those and in hot by the concentrated chamois to - those it is dissolved freely. The majority of salts C. are almost insoluble. From soluble salts C. the greatest value has AgNO caustic silver 3 .

Villages receive generally as a by-product during the melting of the zinc-lead and copper ore concentrates, and also gold-bearing ores containing S.

Methods of definition of ions Ag + include a number of qualitative tests: 1) reaction with diluted salt to - that and its salts with formation of the chloride C. blackening on light owing to decomposition and metal S.'s allocation; 2) reaction with salts monohydroiodide to - you: KI +> AGNShch3 — AgI ↓ + KNO3 (the yellow deposit of silver iodide is formed); 3) reaction with salts chromic to - you: 2AgNO3 + K2CrO4 —> Ag2CrO4 ↓ + 2KNO3 (the deposit of chromate C. of brick-red color is formed); 4) reaction of recovery to metal S. (silver mirror reaction): Ag2O + a reducer (formaldehyde, ions of Mn2+, Sn2 +, etc.) —> 2Ag ↓.

Quantitatively silver is determined by methods of the electrometric analysis, colorimetric and nefelometrichesky methods (see. Colorimetry , Nefelometriya ).

Bactericidal properties of ions Ag + are known to mankind long ago. Silver water with it is insignificant small ion concentration of Ag + (from 2*10 - 11 the g ion/l) is applied to disinfecting of drinking water, and in pharmaceutical industry — to increase in a shelf-life of nek-ry medicines. Believe that this property C. is explained by ability of its ions to block SH groups of enzymes of microorganisms, causing death of a microbic cell. The mechanism of antimicrobic action of connections C. can be also connected with the oppression of the DNA functions of bacterial cells caused by them. In an experiment it is established that ions of Ag + can interact with nitrogen bases thymine and guanine of molecule DNA that is followed by disturbance of the DNA functions and thereof growth inhibition and reproduction of microorganisms.

At local action render the knitting effect due to formation of albuminates at interaction of ions of Ag on skin and mucous membranes of connection C. + with fabric proteins. In high concentration of connection C. possess the cauterizing action.

Through the unimpaired skin and mucous membranes ions of Ag + in blood are practically not soaked up. However their partial absorption can happen during the putting drugs of silver on extensive wound and burn surfaces. Allocation of the soaked-up S. comes from an organism hl. obr. with zhelchyo through intestines.

At long contact with S. and its connections at working at the corresponding productions metal S. it is postponed in connecting fabric, walls of capillaries, in kidneys, a spleen, in marrow, etc. Collecting in skin and mucous membranes, S. gives them a peculiar coloring from gray-green and bluish to borax or flaky-sulfur. Develops so-called. argyrosis (see). The xanthopathy and mucous membranes occurs very slowly and considerable expressiveness reduction of visual acuity, especially in twilight reaches in decades after the beginning of continuous contact from S. Vozmozhna, pointed inclusions in a crystalline lens, discoloration of a pupil and an eyeground. At long contact with S. and its connections inflammatory diseases can develop went. - kish. a path, at the same time note increase and morbidity of a liver, At working with dust of AgBr silver bromide and Ag2S silver sulfide cough, irritation in a throat, cold with bloody allocations from a nose and dacryagogue can develop.

At emergence of the specified disturbances the symptomatic treatment is carried out. Stoppage in the conditions of contact with S. and its connections is recommended.

Acute poisoning of S. and its connections meets rather seldom and usually arises at accidental or deliberate (in the suicide purposes) administration of drugs of S. inside. Under production conditions acute poisonings can take place at massive inhalation of oxide of silver. In case of oral administration of drugs C. the main symptoms of poisoning are nausea, vomiting, abdominal pains and on the course of a gullet. Emetic masses has white color (because of presence of the silver chloride which is formed in a stomach) and on light gets dark coloring. Easily dissociating drugs C. (silver nitrate, protargol) cause chemical burns of a mucous membrane of a mouth, gullet and stomach in this connection in hard cases development of burn shock is possible. At slight poisonings of resorptive effect of drugs C. usually do not observe since ions of Ag + are badly soaked up because of education on a mucosal surface of a cover of albuminates. Besides, a considerable part of ions of Agf reacts in a stomach with salt to - that therefore it is formed insoluble, a little dissociating and not soaking up AgCl silver chloride. Only at intake of large amounts of AgN03 silver nitrate emergence of signs of resorptive action of S. — spasms, falloff of the ABP is possible. disorders of breath. Death at acute poisonings with drugs of silver comes at the phenomena asphyxia (see).

First aid at acute poisonings with connections C. consists in a plentiful gastric lavage of 1 — 2% solution of sodium of chloride, to-ry transfers ions of Ag + to not soaking up chloride C. then inside appoint active coal. Further treatment — symptomatic. At poisonings with connections C. antidotes from group of complexons (Unithiolum, etc.) are inefficient, and Natrium thiosulfuricum (see) it is contraindicated since forms the soluble complexes possessing kapillyarotoksichesky action with S.

Silver in the medicolegal relation. At a research of a corpse of the person who died as a result of poisoning with connections C. note irritation of mucous membranes of a mouth, gullet and stomach, their gray color; in a liver and kidneys — destructive changes. Histologically in tissues of internals it is possible to reveal parts metal S.

Sud. - chemical definition of S. is made by a fractional method in a minerali-zata of fabrics of a corpse. The reaction consisting in S.'s sedimentation in the form of the chloride (a white amorphous deposit) which is dissolved in ammonia and again formed at action of surplus nitric to - you is specific. Use also reaction of formation of a monosubstituted ditizonat of Page. Quantitative definition of S. is made titrimetric (titrate solution of ammonium rhodanide, the indicator — dithizon) or a fotometrirovaniye on a monosubstituted ditizonatus. Sensitivity of a fractional method — 1 mg of S. in 100 g of fabric; this method C. in human organs normal did not found.

Drugs of silver

as pharmaceuticals in medical practice use nek-ry inorganic (e.g., silver nitrate) and organic (e.g., silver Sulfadiazinum) connections C. Besides, concern to group of drugs C. so-called colloid S.'s drugs — colloid silver (see) and protargol (see).

Pharmakol. properties of drugs C. are defined specific biol. ion activity of Ag+ which are formed at dissociation of its connections. The highest extent of dissociation characterizes silver nitrate, by the smallest — protargol. Drugs C., almost not water soluble (colloid silver, silver Sulfadiazinum), possess rather low extent of dissociation.

One of the main pharmakol. properties of drugs C. their antimicrobic action is. In medical practice drugs C. use preferential as antiseptic agents (see. Antiseptic agents ). Silver nitrate and protargol apply the same as astringents (see). In some cases silver per se nitrate or in the form of the concentrated solutions is used in quality caustics (see), napr, for cauterization of excess granulations, condylomas, warts, etc.

Silver nitrate (Argenti nitras; synonym: lyapis, Argentum nitri-eum; GFH, joint venture. A; AgN03) — colourless transparent crystals in the form of plates or white cylindrical sticks, inodorous, under the influence of light darken, very easily rastvorima in water, are difficult alcohol-soluble. In the presence of organic matters of silver nitrate decays, with halogens forms a deposit. Possesses the bactericidal and knitting action. In high concentration renders the cauterizing effect. Apply outwardly at erosion, cracks, acute conjunctivitis, trachoma, hron. hyperplastic laryngitis, etc. Appoint in the form of 2 — 5 — 10% of water solutions and 1 — 2% of ointments. As priishgayu-shchy means is used also in the form of so-called lyapisny pencils (Stilus Argenti nitratis). As the knitting and local anti-inflammatory drug sometimes apply inside in the form of 0,05 — 0,06% of water solution at hron. gastritis and peptic ulcer of a stomach.

The highest doses for adults inside: one-time 0,03 g, daily — 0,1 g.

Form of release: powder. Store in well corked banks with a ground stopper, in the place protected from light.

Silver nitrate together with silver chloride is used also for preparation bactericidal paper (see).

Silver Sulfadiazinum (Silver sulfadiazine; synonym: Dermasinum, Dermazin, Flamazine, Silvertone, etc.) C10H9AgN4O2S):


Antibacterial effect of drug is caused by the ions of Ag which are formed at its dissociation + and the rest of Sulfadiazinum, to-ry on a chemical structure and properties belongs to sulfanamide drugs. Apply to treatment of burns. Appoint in the form of cream, to-ry apply on burn surfaces with a layer 2 — 4 mm several times in days.

Drug is contraindicated to use for newborns and at pregnancy. With care persons should appoint drug with hypersensitivity to streptocides and persons with genetically caused insufficiency of enzyme of a glyukozo-6-phosphate-dehydrogenase in erythrocytes (in connection with danger of development of hemolitic reaction).

Form of release: 1% cream in tubas on 50 g or in banks on 250 g.



Bibliography: Glazov O. I. Poisonings and first aid at them, page 28, M., 1944; Krylova A. N. A research of biological material on «metal» poisons by a fractional method, page 47, M., 1975; Levin V. I. Receiving radioisotopes, page 180, M., 1972; M and sh to about in with to and y M. D. Pharmaceuticals, the p. 2, with. 353, M., 1977; N e-krasov B. V. Fundamentals of the general chemistry, t. 2, page 210, etc., M., 1973; Crybabies and I. N. Metallurgiya's N of noble metals, page 63, M., 1958; Fox of Page L. and. M about d a k S. M of Mechanism of silver sulfadiazine action on burn wound infections, Antimicrob. Agents Chemother., v. 5, p. 582, 1974; The pharmacological basis of therapeutics, ed. by A. G. Gilman a. o., N. Y., 1980.


V. V. Bochkaryov; A. F. Rubtsov (court.), V. K. Muratov (pharm).

Яндекс.Метрика