Consider some methods for producing silver, as well as focus on its physical and chemical properties. This metal attracted people even in ancient times. Silver owes its name to the Sanskrit word "argenta", which translates as "light". From the word "argenta" the Latin "argentum" also came.
Interesting Origin Facts
There are many versions about the origin of this mysterious metal. All of them are connected with the Ancient World. For example, in Ancient India, silver was associated with the Moon and Sickle - the oldest instrument of the farmer. The gleam of this noble metal is similar to the light of the moon, therefore, in the alchemical period, silver was designated as the symbol of the moon.
Silver in Russia
In ancient Rus, silver bars were a measure of the value of various objects. In those cases when some item of trade cost the least of the bar, a part corresponding to the indicated value of the thing was cut off from it. These parts were called "rubles," It was from them that the name of the currency adopted in Russia came from - the ruble.
Even 2500 years before our era, Egyptian warriors used silver to treat military wounds. They placed thin plates of silver on them, and the wounds healed quickly. In the Russian Orthodox Church, holy water for parishioners was kept only in silver vessels. Since the middle of the last century, such industries as photography, electrical engineering, and radio electronics have appeared, which led to a sharp increase in demand for silver and its withdrawal from monetary circulation.
High electrical conductivity, good ductility, low melting point, and low chemical activity of silver also interested radio engineers.
Feature Description
All methods for producing silver are based on its properties. This is a white metal, practically unchanged under the influence of atmospheric oxygen at room temperature. Due to the presence of hydrogen sulfide in the air, it eventually becomes coated with a dark coating of silver sulfide Ag 2 S. This compound is removed mechanically from the surface of the silver product using cleaning pastes or fine tooth powder.
Silver is quite resistant to water. Hydrochloric acid, as well as diluted sulfuric acid and aqua regia do not act on it, since a protective film of its chloride AgCl is formed on the surface of the metal.
The production of silver nitrate is based on the ability of a metal to react with nitric acid. Depending on its concentration in the reaction products, in addition to silver, nitrogen oxides (2 or 4) can also be present.
The production of silver oxide is carried out by adding an alkali solution to silver nitrate. The resulting compound has a dark brown color.
Areas of use
Due to the physical and mechanical properties, it is silver that covers radio components to increase electrical conductivity and corrosion resistance. Silver metal is used in the manufacture of silver electrodes for various types of modern batteries. Electroplating silvering and nickel plating were dealt with for a long time by specialists in the field of electroplating: A.F. and P.F. Simonenko, A.P. Sapozhnikov and others I.M. Fedorovsky moved the issue regarding the corrosion resistance of coatings from the laboratory to industrial production. Silver compounds (AgBr, AgCl, AgI) are used for the production of film and photographic materials.
Electrolysis of salt solutions
Consider obtaining silver by electrolysis of its salts. An electrical circuit is assembled in which a galvanic dry cell acts as a current source. The maximum current in the circuit should not exceed 0.01 A. When using a dry battery (4.5 V), the current is limited by the addition of a conductor with a resistance of not more than 1000 Ohms.
Any glass vessel can serve as a bathtub for the silvering process. The anode of the bath is a plate of metal having a thickness of 1 mm and an area slightly larger than that of the part itself. Silver is chosen for the anode coating. As a working solution (electrolyte) for obtaining silver, a lapis solution is used. Before lowering into the silvering bath, degrease and polish the part, then wipe it with toothpaste.
After removing the fat, it is washed with running water. You can judge the complete degreasing by uniformly wetting the entire surface of the part with water. When washing, use tweezers to prevent greasy finger marks on the parts. Immediately after washing, the part is fixed on the wire and placed in the bath. The time to obtain silver with a silver anode is 30 to 40 minutes.
If stainless steel is chosen as the anode, then the speed of the process changes. Getting silver from nitrate will be 30 minutes.
The part removed from the bath is thoroughly washed, dried, and polished to a shine. With the formation of a dark silver precipitate, the current decreases, for this additional resistance is connected. This improves the quality of silver by the electrochemical method. For uniform coating during the electrolysis, the part is periodically rotated. You can put metal on brass, steel, bronze.
Process chemistry
What processes are associated with obtaining silver? Reactions are based on the location of the metal after hydrogen in a number of standard electrode potentials. At the cathode, silver cations will be reduced from its nitrate to pure metal. At the anode, water is oxidized, accompanied by the formation of gaseous oxygen, since lapis is formed by oxygen-containing acid. The total electrolysis equation has the following form:
4Ag NO 3 + 2H 2 O electrolysis 4Ag + O 2 + 4HNO3
Getting in the lab
The working solution (electrolyte) can be spent fixer, in which silver cations are present. The halides of this metal form a number of complex salts with thiosulfate. During electrolysis, silver - metal is released at the cathode. Obtaining it in a similar way is accompanied by the release of sulfur, which leads to the appearance on its surface of a thin black layer of silver sulfide.
Production and discovery
The first mention of silver mining is associated with deposits that were discovered by the Phoenicians in Cyprus, in Sardinia, Spain, and Armenia. The metal was present in them in conjunction with sulfur, chlorine, arsenic. It was possible to detect native silver of impressive size. For example, the largest nugget of silver is the sample, whose weight was thirteen and a half tons. When cleaning natural nuggets with molten lead, a dull metal was obtained. In ancient Greece, it was called Electron, predicting its excellent conductive properties.
Currently, a dense layer of metallic silver is produced by electrolysis. As an electrolyte, not only nitrate is used, but also cyanides. Silver is separated from copper by electrolysis from a cold solution, in which about one percent of sulfuric acid, 2-3% of potassium persulfate are present. About 20 mg of metal can be separated from copper in 20 minutes using a voltage of about 2 V.
During electrolysis, an excess of potassium persulfate should remain in solution. Also, among the options for the separation of these metals, electrolysis of a boiling acetic acid mixture can be considered. Currently used techniques involving the use of complexants. In a solution that contains ethylenediaminetetraacetic acid ion (EDTA) in an acidic environment, silver precipitates in 25 minutes. It is separated from the plate by electrolytic deposition for 2.5-3 hours.
Silver is separated from bismuth and aluminum by electrolysis of a nitric acid solution under conditions similar to the separation of its mixture with copper.
Conclusion
It should be noted that the preparation of silver acetylenide is a qualitative reaction in organic chemistry to the presence of acetylene and other alkynes in the mixture in which the triple bond is in the first position. On an industrial scale, silver is used in the electrical and metallurgical industries. It is a by-product in the processing of complex metal sulfides, which contain argenite (silver sulfide).
In the process of pyrometallurgical processing of polymetallic zinc sulfides, copper, silver is extracted together with the base metals as silver-containing compounds. In order to enrich pure silver with silver-containing lead, use the Parkes or Pattison process. The second method is based on cooling molten lead in which there is silver. Metals have different melting points, so they will precipitate and separate from the solution in turn. Patisson suggested exposing the remaining liquid to oxidation in a stream of air. The process was accompanied by the formation of bivalent lead oxide, which was removed, and the silver remaining in the molten form was purified from impurities.
Even in ancient Greece, the method of producing silver by cupellation was used.
This technology is currently used in industry. The method is based on the ability of molten lead to oxidize with oxygen in the atmosphere.