Silver

SILVER, Argentum (Ag), a chemical element, a metal, atomic weight 107.880, is located in the 7th row of Group I of Mendeleev's periodic system of elements. Silver occurs in nature in native form as well as in compounds with sulfur, selenium, tellurium, arsenic, and halogens. Silver is a common companion of lead ores (in the form of Ag₂S), from which it is predominantly extracted. Significant quantities of silver are mined in America (USA and Mexico); silver is also mined in the USSR (Nerchinsk, Caucasus). The specific gravity of silver is 10.5. Under ordinary conditions, silver is a rather soft metal, malleable and ductile (it can be made into the thinnest threads). Silver has good thermal and electrical conductivity. In a very thin layer, silver in transmitted light has a bluish tint. Silver melts at a temperature of about 1000°C and gives bluish vapors. Silver dissolves well in strong nitric acid, turning into silver nitrate. Strong sulfuric acid dissolves silver only when heated. Hydrochloric acid, dilute sulfuric acid, and alkalis do not act on silver. When hydrochloric acid or solutions containing chloride ions are added to solutions of silver salts, insoluble silver chloride precipitates, which is usually used to detect silver (after separating it from other substances that give precipitates with chlorine). Pure silver is used only in laboratory practice. In ordinary articles, alloys of silver with copper are used. Silver compounds are sensitive to light, especially halide compounds, which find application in photography: under the influence of light and subsequent treatment (development), the bromide compound of silver is reduced to the metallic state and gives a black image of the photographed object. According to its pharmacological action, silver belongs to the group of heavy metals. It is necessary to distinguish between the action of preparations that release free silver ions and the action of silver in the colloidal state. Preparations of silver that release its free ions are used for their local and disinfectant action. Regarding colloidal silver, see Collargol. The essence of the disinfectant action lies in the fact that silver ions form compounds with the protein of bacteria and thus lead to their death. A commonly used preparation is silver nitrate (AgN0₃). When it acts locally on the mucous membrane or wound surface, silver albuminates are formed, initially white in color, turning black under the influence of light. When using weak solutions (1:1000 and weaker), only a surface astringent effect is obtained; in the case of using more concentrated solutions (1% and higher), a cauterizing and irritating effect is obtained. The cauterizing action of silver is inferior to that of mercury but significantly exceeds the action of lead. The cauterizing action of silver is relatively superficial, since in the tissues it turns into insoluble silver chloride. The irritating action of silver promotes the dilation of local blood vessels, which may be important in a number of local processes. With accidental ingestion of silver nitrate or its strong solutions, there is severe irritation of the entire gastrointestinal tract, as a result of which vomiting, severe pain in the abdomen and esophagus, and diarrhea occur. Due to reflex influences on the central nervous system, collapse and death may occur. If survival occurs, the cauterizing action of silver on the gastrointestinal mucosa can lead to very serious consequences (perforations, strictures, etc.). When acting locally on the skin, silver does not produce a noticeable effect, but can penetrate into its thickness. Under the influence of light it turns black—black spots appear, which is sometimes observed in people dealing with silver (photographers). The phenomenon is called local argyria. Absorption of silver, when its salts are taken internally, usually does not occur. Absorption of silver is hindered by its astringent action on the mucous membrane, as well as by the fact that in the presence of hydrochloric acid of gastric juice, it can turn into insoluble silver chloride. In addition, silver in the gastrointestinal tract forms with the food masses present there poorly dissociating albuminates. However, with prolonged use of silver, it has been found in the tissues of the villi lying deeper than their epithelial covering. The presence of ulcerated surfaces devoid of epithelium may facilitate the absorption of silver. When silver is absorbed from the gastrointestinal tract, no noticeable symptoms of its action are observed, but histological examination can detect it in a number of organs: in the aorta, liver, kidneys, and the layer of proper skin. Apparently, silver in the body is quickly reduced to the metallic state, is captured by reticuloendothelial cells, and then deposited in the aforementioned organs. Silver deposited in the skin, depending on its quantity, gives the skin a light gray or even black color (see Argyria). Direct introduction of silver nitrate or other well-dissociating preparations into the blood is impossible, because due to blood clotting, death will occur from embolism. For the purpose of studying the resorptive action in experiments on animals, soluble silver albuminates or other poorly dissociated compounds were used. In this case, at first there was a short-term increase in respiration, an increase in blood pressure, a slowing of the pulse (exciting action on the medulla oblongata), soon however respiration slowed, blood pressure fell, and death occurred from paralysis of the respiratory center. The heart survived the cessation of respiration. It is interesting to note that with acute poisoning by silver, death occurs with symptoms of pulmonary edema due to transudation of fluid into the lumen of the bronchi. In non-fatal poisonings, paralysis of the hind limbs was observed. In frogs, convulsions are noted. When silver is absorbed from the gastrointestinal tract, it is not found in the urine. When silver is introduced into the blood (in experiments on animals) with a relatively small dose, increased kidney activity is observed, with large doses—anuria, i.e., phenomena similar to those with other heavy metals. Silver salts are used on mucous and wound surfaces for their astringent, cauterizing, and antiseptic action. The strength of action of different silver preparations depends on their degree of dissociation. Salts of inorganic acids (nitrate) have a stronger effect than weakly ionized organic compounds of silver or its compounds with protein. At the same time, the action of the anion must also be taken into account: the nitric acid released from AgN0₃ will also act cauterizingly. Silver is widely used in the treatment of gonorrhea (douches). The irritating action of ordinary silver nitrate led to the search for a number of other preparations with a milder effect. Most often these are some combination of silver with protein. In gonorrhea, silver is also used prophylactically: after suspicious coitus, relatively strong solutions of it (up to 5% AgN0₃) are introduced into the fossa navicularis of the urethra. Silver is used in soft chancre; in purulent processes on wound and mucous surfaces. In sluggish purulent granulations, on the one hand, the antiseptic and astringent action of silver is expected, on the other hand, it is expected that the removal of mucoid degenerated granulations (cauterizing action) and irritation of the tissues will lead to more powerful development of new granulations. At present, silver is almost never administered internally. Previously, it was often prescribed for its astringent action in stomach ulcers and various intestinal disorders, however, the conversion of silver into insoluble compounds in the stomach, painfulness, the danger of argyria, and the lack of sufficient therapeutic effect make its use useless. Silver was also prescribed for a number of nervous diseases: chorea, epilepsy, tabes dorsalis, some mental diseases. However, no improvement was noted with this. Ionized silver preparations are not administered intravenously. Regarding the oligodynamic action of silver, see Oligodynamic action. Silver preparations are used: in substance for cauterizing action; in solutions—for cauterizing or astringent and antiseptic action. The strength of the solutions depends on the properties of the preparation. Internally, silver is prescribed in the form of drops or pills. When making pills of silver nitrate, organic substances cannot be used to avoid the decomposition of AgN0₃ upon contact with organic substances, therefore silver pills are usually prescribed with bolus alba. All silver preparations must be protected from the action of light. 1. Argentum nitricum crystallisatum, s. Lapis infernalis—silver nitrate, lapis, infernal stone (Ph VII). White crystals, readily soluble in water (1 part in 0.4 parts of water), less soluble in alcohol (1:26), difficult to dissolve in ether. When calcined, it decomposes with the formation of nitrogen oxides. A widely distributed preparation; well dissociates in solutions. It can be cast into sticks, pencils. Used cauterizingly in substance or in 5-10% solutions; as an astringent—0.1-0.2%. 2. Argentum nitricum cum kalio nitrico, s. Lapis mitigatus—silver nitrate, fused with potassium nitrate. Made in the form of cast sticks.

The ratio of salts varies in different pharmacopoeias, ranging from 1 part AgNO₃ to 2 parts KNO₃ (German pharmacopoeia) to 9 parts AgNO₃ to 1 part KNO₃ (Belgian pharmacopoeia). In the USSR, it is not official. Its use is similar to the previous one, but due to the addition of another salt, its effect is milder. - 3. Argentum chloratum, m-chloride of S. Insoluble in water. Soluble in 10% ammonia solution. Prescribed internally as an astringent for diseases of the gastrointestinal tract (gastralgia, chronic diarrhea) and, which is hardly justified, for nervous diseases (epilepsy, chorea); internally 0.02 in pills.-4. Actol, s. Argentum lacticum- actol, lactic acid S. White crystalline powder. Soluble in 15 parts water. 5. Argonin, s. Argentum caseinicum (see Protargol). Poorly soluble in cold water, well in hot water. Used in gonorrhea (douches) in 1.5-3% solutions. Internally--0.1, daily dose up to 0.3.--6. Nesagol, necaron--obtained by precipitating with alcohol or acetone a solution of 1 mole of potassium silver cyanide and 1 mole of potassium chloride. Soluble in water, difficult in alcohol. Has a faint smell of hydrocyanic acid. Prescribed like the previous one.-7. Itrol, s. Argentum citricum, citric acid S, itrol. White, heavy powder, poorly soluble (1:3,800). Used in solutions of 1:4,000-1:10,000 for washing in gonorrhea. Does not irritate. Also used in ointments (1:100) and suppositories (2%). Internally-0.03, daily dose-0.1.--8. Nargol, s. Argentum nucleinicum-nargol, or nucleinic acid S. Light brown powder. Contains 10% S. Soluble in water. Externally in gonorrhea in 1-2% solutions. Prophylactically 10% solutions.-9. Argyrol--compound of S. with egg nucleoalbumin. Contains 30% S. Soluble in water. Used in ophthalmic practice.-10. Sorhol, sorhol - formaldehyde-nucleinic acid S. Used in ophthalmic practice, especially in gonorrhea of the eyes in newborns.- 11. Neo-Reargon, neo-reargon--compound of S. with anthraquinone. Reddish-brown powder. Solutions are colored red wine and have an alkaline reaction. Externally in gonorrhea in 0.5--5% solutions.- 12. Ichtargan, ichtargan, and Neoichtargan, neoichtargan--compound of S. with ichthyol (see). Neoichtargan-black, water-insoluble powder, odorless. Contains 12.5% S. and 15% sulfur. Most of the sulfur (11.3%) is in sulfide form. Prescribed in eczemas in 2% ointments.-13. Argochrom, argochrom--combination of silver nitrate with methylene blue. Contains 20% S. Prescribed externally for buboes, furuncles, inflammation of the middle ear. In malaria, septic diseases, joint rheumatism--under the skin 2-20 cm³ of 1% solution or up to 20 cm³ of 0.5-1% solution into a vein. When preparing solutions for intravenous and subcutaneous administration, one cannot use physiological solution or add NaCl (embolism!).-14. Argentamin, argentamin--solution of 10 parts silver nitrate and 10 parts ethylenediamine [C₂H₄(NH₂)₂] in 80 parts water. Colorless liquid of alkaline reaction. Prescribed externally in gonorrhea and ophthalmic practice in dilutions 1:400-1:500. Unstable preparation. Gives precipitates with proteins and NaCl.- 15. Albargin, albargin--colloidal preparation of AgOH, protected by gelatin hydrolysate (gelatose). Light brown shiny powder, contains 15% S. Soluble in water. In gonorrhea, externally-0.1- 0.2% solution.-16. Novargan, novargan--protein compound of S, similar to protargol (see).-17. Orotol, orotol--protein compound of S. Insoluble in water. Contains 10% S. Used as a powder or aqueous suspension 2:100 in the treatment of wounds, removal of diphtheritic membranes and gonorrhea. 18. Largin, largin--compound of S. with vegetable protein. At present, its production has been discontinued.- 19. Collargol-see Colyargol.-20. Protargol-see Protargol. 21. Electragol-see Colyargol. The last three preparations are used for intravenous infusions (general septic processes). Silver is used for staining tissues in histological practice.

A. Vasiliev. Discovery in legal cases. Parts of internal organs, stomach and intestinal contents, vomit are destroyed with the help of hydrochloric acid and potassium chlorate (see Poisons, isolation), the liquid after chlorine removal is filtered, the precipitate is fused with soda and saltpeter. The sulfur alloy is extracted with hot water, the residue is well washed (until the chlorine reaction ceases) and dissolved in concentrated nitric acid. The solution is dried to dryness, the residue is dissolved in the smallest possible amount of water and examined for the presence of S ions: 1) with hydrochloric acid solution: a white curdy precipitate is obtained, insoluble in nitric acid, but easily passing into solution from ammonia; 2) with potassium dichromate solution: a red coloration and precipitate are obtained; 3) reduction of metallic S: to the solution placed in a narrow test tube, a solution of caustic soda is added, then aqueous ammonia until the precipitate dissolves, then 1-2 drops of formalin and heated: a gray turbidity appears from the release of metallic S, and a shiny Silver Mirror forms on the walls of the test tube.

A. Stepanov. Application of silver for water sterilization. In 1928, Krause (G. A. Krause) on the basis of his experimental research proposed for water sterilization its filtration through silvered sand -"katadyn", the filtrate in this case was not only sterile but also possessed a bactericidal effect. The method was patented by the author, and its essence was reduced to the oligodynamic influence of metal silver ions on the body of microbes (see Oligodynamic action). However, the method did not become widespread for sterilizing large masses of water and in practice came down to the same as what so-called household filters gave. Mainly in Germany, jugs filled with katadyn rings of porcelain are used; water poured into them becomes sterile after 2-6 hours depending on its initial properties; there are also installations for small water consumption. This method produced a small amount of literature and has not yet influenced the practice of mass water disinfection in water supply systems.-In the USSR, katadyn was of interest mainly to S. V. Moiseev and V. A. Uglov; they not only disclosed the patent but the first of them proposed a method of silvering sand that is cheaper and even more effective than Krause's sand. Thus, the contact time of water with katadyn sand in Krause is 2 hours (up to 6 hours), in Moiseev-30 minutes; the weight amount of S. on the sand is 10% of the weight of the sand in the first and 0.3% in the second; the cost in the first is 37.5 marks per 1 kg and correspondingly 66 kopecks in the second with complete sterilization of water and its quantity ratio to the amount of sand during contact time 10:1 for both. The necessity of frequent washing of the sand in case of turbidity in the water or its preliminary purification by filtration was firmly established, and according to Moiseev's opinion, coagulation is not applicable in this case, since the fine coagulant turbidity that has passed through the filters will contaminate and weaken the katadyn filter, causing its washing. Since rapid filtration with preliminary coagulation of water is the modern and only profitable method of water purification in water supply systems, the above opinion as it were closes the way for the use of katadyn filters in water supply systems, besides the fact that repeated filtration through silvered sand will require either large reserves of height to compensate for pressure losses during secondary filtration or additional pumping.-In 1932, P. E. Ermolaev (Moscow) came forward with a different theory of the action of S. Working on therapeutic preparations of the latter (protargol, electragol, etc.), he came to the conclusion that the active principle in these preparations is S. salts, not metallic S.; the salts are bactericidal, not metallic S, which in the body and in natural waters forms ammonia compounds due to deamination of protein or ammonia salts. If this point of view is transferred to katadyn, then its active bactericidal principle will not be metallic S. on the surface of the sand grains, but those unwashed S. salts and its oxide that remained from silvering. Hence follows the unnecessity of silvering sand and the direct action of salt solutions on water or the use of salts in solid phase with the addition of ammonia to facilitate the formation of ammonia compounds and regulate solubility. This can open new perspectives in the matter of water purification, since some S. salts possess very significant sterilizing ability in very small concentrations, for example of the order of 0.00154 mg\l for AgCl. The question thus reduces to the technical construction of mixing large masses of water with solutions of very small concentration, which would make this method competitive in cheapness with other methods of water sterilization.

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V. Lazarev. Silvering of root canals - one of the methods for treating teeth with affected pulp, mainly in case of gangrene of the latter. This method is known under the name of the Howe method after its author, who proposed its use during the years of the world war. In our republic, the method of silvering root canals has become quite widespread since 1924 after the publication of a work on this question by Govseev. The essence of this method consists in the introduction into the root canal of the tooth of various solutions of silver with subsequent reduction by an appropriate reducing agent. Thanks to the deep diffusion force of silver solutions and its reducing agents, silver penetrates deeply into the dental tissues and is deposited in the dentinal tubules* and in the apical ramifications of the root (in the so-called regio ramification, pulpae), i.e., in all those parts of the root that are inaccessible to mechanical and medicinal treatment. With the remains of pulp decay, the silver solution enters into a chemical bond, turning into a sterile mass of silver albuminates, which cannot serve as a soil for the further development of microorganisms. The method of silvering root canals has its classic form of application according to Howe and a number of modifications. According to Howe, an ammoniacal solution of silver is used as the solution, which is schematically prepared as follows: 3.0 grams of silver nitrate is dissolved with slight heating in 1 cm³ of distilled water; a dark liquid is obtained, to which gradually drop by drop is added ammonia spirit (Liq. ammon. caustici) approximately 12-13 cm³, until the entire solution becomes transparent with a small fine precipitate at the bottom of the test tube. The reaction proceeds according to the formula: AgN0₃ + NH₄OH = AgOH + NH₄N0₃. As a reducing agent, Howe proposed a 10% solution of formaldehyde, i.e., a 25% solution of formalin; the latter eagerly removes oxygen from silver hydroxide. The reaction is schematically as follows: 2AgOH + HCHO (formaldehyde) = 2Ag + HCOOH + H₂O, i.e., silver, formic acid and water are obtained. The treatment of a tooth by silvering according to Howe can be practically carried out in one session. After opening the pulp chamber and removing the decay, the ammoniacal solution of silver and formalin are introduced drop by drop with tweezers or a special pipette into the orifices of the root canals. This procedure is repeated 4 times (4-phase method of treatment): 2 times the solutions are introduced into the orifices of the canals, then after freeing the root canals from decay, the solution and its reducing agent are pumped twice directly into the root canal, after which the tooth is filled. Modifications of the Howe method include the methods of Rikkert, Schaer, and Goldschmidt. The first two authors, instead of formaldehyde, which they quite rightly consider a strong irritant for the periodontium, proposed other means for reduction: Rikkert - essential oils (clove oil and especially eugenol), Schaer - glucose. Goldschmidt's modification consists both in changing the composition of the silver solutions and its reducing agent. He proposes them in two variants: 1) a 2.5% alcoholic solution of lunar caustic and a reducing agent - a 4% alcoholic solution of gallic acid; 2) a 5% alcoholic solution of lunar caustic, a reducing agent - a 4% alcoholic solution of pyrogallic acid. Histological examination of the root after silvering indeed shows a rather deep impregnation of silver and therefore silvering belongs to the so-called impregnation methods of root treatment. Silvering of root canals is especially widely recommended for use in pediatric practice, when the apical part of the root has not yet formed and does not allow for extirpation of the pulp during treatment. Howe, Rikkert, and after him Govseev, propose the application of the silvering method not only in case of pulp gangrene, but also in deep caries for the purpose of sterilizing the infected dentin and also for covering an accidentally exposed pulp. Silvering of root canals, despite all the apparent attractiveness of this method at first glance, has however a whole series of major shortcomings that strongly limit its application: 1) Silver solutions cause strong darkening of the tooth, which makes them absolutely inapplicable on front teeth and relatively inapplicable on all other teeth. Attempts to isolate the crown of the tooth from the staining action of silver did not give significant results. 2) Silvering is associated with a considerable expenditure of time for treatment--the patient has to in the case of single-session treatment remain with an open mouth for half an hour or more. 3) The diffusion of silver is rarely complete and some areas of the root with infected tissue remain without the action of silver. 4) Silvering of root canals does not guarantee the tooth from damage to the periodontium; observations as well as clinical, and in particular experimental (works of Feldman) have convincingly shown the irritating effect of silver solutions and its reducing agents on peri-apical tissues.