Let's consider some ways to obtain silver, and also dwell on its physical and chemical properties. This metal has attracted people since ancient times. Silver owes its name to the Sanskrit word "argenta", which translates as "light". From the word "argenta" came the Latin "argentum".
Interesting facts about origins
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 the Sickle, the most ancient tool of the farmer. The reflection of this noble metal is similar to the light of the moon, therefore, in the alchemical period, silver was designated as a symbol of the moon.
Silver in Russia
In ancient Russia, silver bars were a measure of the cost of various items. In those cases when some item of trade cost the least bar, from itcut off a part corresponding to the indicated value of the item. These parts were called "rubles", It was from them that the name of the monetary unit adopted in Russia came - the ruble.
As far back as 2500 BC, Egyptian warriors used silver to treat battle wounds. They put 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, radio electronics have appeared, which led to a sharp increase in demand for silver, its withdrawal from money circulation.
High electrical conductivity, good ductility, low melting point, low chemical activity of silver also interested radio engineers.
Characterization of properties
All methods of obtaining silver are based on its properties. It is a white metal, practically unchanged by atmospheric oxygen at room temperature. Due to the presence of hydrogen sulfide in the air, it eventually becomes covered with a dark coating of silver sulfide Ag2S. Remove this compound from the surface of the silver product mechanically, using cleaning pastes or fine tooth powder.
Silver is quite resistant to water. Hydrochloric acid, as well as dilute sulfuric acid and aqua regia, do not affect it, since a protective film of its chloride AgCl is formed on the surface of the metal.
Obtaining silver nitrate is based on the ability of the metal to enter intoreaction with nitric acid. Depending on its concentration, in addition to silver, nitrogen oxides (2 or 4) may be present in the reaction products.
Obtaining silver oxide is carried out by adding an alkali solution to silver nitrate. The resulting compound is dark brown.
Applications
Due to its physical and mechanical properties, it is silver that is used to coat radio components to increase electrical conductivity and corrosion resistance. Metallic silver is used in the manufacture of silver electrodes for various types of modern batteries. The issues of electrolytic silvering and nickel plating have been de alt 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 transferred the issue of anti-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 s alt solutions
Consider the production of silver by electrolysis of its s alts. 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 adding a conductor with a resistance of not more than 1000 ohms.
Any glass vessel can serve as a bath for the silvering process. The anode of the bath is a plate of metal having a thickness of 1 mm and a slightly larger area,than the part itself. Silver is chosen for anodic coating. Lapis solution acts as a working solution (electrolyte) for obtaining silver. Before lowering into the bath for silvering, it is necessary to degrease and polish the part, then wipe it with toothpaste.
After removing fat, it is washed with running water. Complete degreasing can be judged by uniform wetting of the entire surface of the part with water. When washing, use tweezers so that no greasy fingerprints remain on the part. Immediately after washing, the part is fixed on the wire and placed in the bath. Silver production time with silver anode is 30 - 40 minutes.
If stainless steel is chosen as the anode, then the process speed changes. Obtaining silver from nitrate will be 30 minutes.
The item taken out of the bath is washed, dried, polished to a shine. With the formation of a dark silver deposit, the current decreases, for this an additional resistance is connected. This makes it possible to improve the quality of obtaining silver by the electrochemical method. For uniformity of the coating during the electrolysis process, the part is periodically rotated. You can deposit metal on brass, steel, bronze.
Chemistry of the process
What are the processes associated with obtaining silver? The 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 gaseousoxygen, since lapis is formed by an oxygen-containing acid. The overall electrolysis equation is as follows:
4Ag NO3 + 2H2O electrolysis 4Ag + O 2 + 4HNO3
Laboratory Obtaining
The working solution (electrolyte) can be used fixer, which contains silver cations. The halides of this metal form a series of complex s alts with thiosulfate. During electrolysis, silver is released at the cathode - a metal. Obtaining it in a similar way is accompanied by the release of sulfur, which leads to the appearance of a thin black layer of silver sulfide on its surface.
Extraction and discovery
The first mention of silver mining is associated with deposits that were discovered by the Phoenicians in Cyprus, Sardinia, Spain, Armenia. The metal was present in them in combination with sulfur, chlorine, arsenic. It was also possible to detect native silver of impressive size. For example, the largest silver nugget is a sample weighing thirteen and a half tons. When cleaning natural nuggets with molten lead, a dull metal was obtained. In ancient Greece, it was called Electron, anticipating its excellent electrical conductive properties.
Currently, a dense layer of metallic silver is produced by electrolysis. As an electrolyte, not only nitrate, but also cyanides are used. The separation of silver from copper is carried out by performing electrolysis from a cold solution, which contains aboutone percent sulfuric acid, 2-3% potassium persulfate. About 20 mg of metal can be separated from copper in 20 minutes using a voltage of about 2 V.
In the process of electrolysis, an excess of potassium persulfate must remain in the solution. Also among the options for the separation of these metals, one can consider the electrolysis of a boiling acetic acid mixture. Currently, methods are used that involve the use of complexants. In a solution that contains an ion of ethylenediaminetetraacetic acid (EDTA) under 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
Note that the production 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 located 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 containing argenite (silver sulfide).
In the process of pyrometallurgical processing of polymetallic sulfides of zinc, copper, silver is extracted together with base metals as silver-containing compounds. In order to enrichpure silver of silver-containing lead, use the Parkes or Pattison process. The second method is based on the cooling of molten lead, which contains silver. Metals have different melting points, so they will alternately precipitate and stand out from solution. Patisson proposed to subject the remaining liquid to oxidation in an air stream. The process was accompanied by the formation of divalent lead oxide, which was removed, and the silver remaining in the molten form was purified from impurities.
Even in ancient Greece, the method of obtaining silver by cupellation was used.
This technology is still used in industry. The method is based on the ability of molten lead to be oxidized by atmospheric oxygen.
