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Characteristics of different alloys of silver and copper

Silver has been loved and loved all over the world and is often preferred to the more valuable gold. Various things have been made from this beautiful light metal for centuries: cutlery, candlesticks, caskets, etc. However, it is most widely used in jewelry. Skilled craftsmen used all their imagination to make intricate rings, earrings, bracelets, necklaces and pendants from precious metal to adorn the bodies of kings, princesses and wealthy citizens. Today, silver is considered a “feminine” metal, since silverware is more worn by the fair sex. But often silver chains can be seen on men's necks.

Not everyone can afford pure silver jewelry, as they have a high cost. In addition, the metal of the highest standard is impractical. It is soft so it scratches easily. Openwork made from it jewelry with daily wear, they quickly lose the expressiveness of the relief and are no longer as beautiful as before. Therefore, silver alloys with other metals (ligatures) are used in jewelry. Different types of alloys give the precious material hardness and increase its wear resistance. Thanks to ligatures modern jewelers can make silver jewelry using the most complex technique. What are the silver alloys?

The influence of metals on the quality of the alloy

In the modern world, copper is added to liquid silver as a common ligature, it is believed that these 2 metals interact well with each other.

Introduced into alloys with or without copper also a small amount of nickel, cadmium, zinc and other impurities that not only improve the quality of silver products, but can also worsen them.

So, if 1% nickel is present in the alloy, then its strength increases, while at a content of 2.6%, the impurity makes the alloy brittle. If more than 9% tin is added to silver-copper alloys, it begins to melt, oxidize and increase the brittleness of the ligature. For the same reason, the content of more than 6% aluminum in the alloy is undesirable. Cadmium and zinc reduce the melting point, are resistant to air tarnishing, are ductile, and work well. If the alloy contains from 15 to 21% zinc, it beneficial features are reduced to nothing. Copper combined with cadmium forms a rather brittle compound. The content of silicon and lead should not exceed more than 1.5% in the combination of silver with copper, since it becomes brittle, and phosphorus, sulfur and lead should not be present at all in the precious metal as ligatures.

Because of the above problems, jewelers prefer to add the best metal for it - copper - to pure silver. From 5 to 50% of this golden-pink metal can be introduced. With a low copper content in the alloy, the products look great and are close to pure metal in appearance.

The more copper is contained in the compound, the more its color will differ from pure silver. If a finished jewelry have a slight reddish tint, this is the first sign that the alloy contains 50% copper. If the reddening of the product is pronounced, this indicates the presence of more than 50% copper in it. Jewels of this type are very common in the markets of Arab countries, and sellers assure gullible tourists that they contain at least 60% silver. Although silver items are cheaper in the Eastern markets, it is better to buy them in specialized stores. This will serve as a guarantor of the quality of jewelry and help to avoid buying fakes.

How to understand silver samples?

Samples help to find out how many percent of copper is added to the precious metal: their number, consisting of 3 digits, indicates how many grams of pure silver are contained in 1 kg of the alloy. In world jewelry practice, there are specially adopted standards for testing silver and gold alloys, which manufacturers must comply with. precious jewelry. In Asian countries, jewelry masterpieces of the 600th test are produced, although they are not of high quality and quickly lose their appearance.

According to international standards, Ag 720 is considered the lowest breakdown. Although this alloy has a slight yellowness, it is used in Russia in jewelry workshops for making locks and clasps for chains and necklaces.

From alloys of the 750th and 800th test, cutlery and dishes are produced. For products from these samples, you need permanent care because they quickly oxidize in air.

Silver of the 830th and 875th tests is suitable as a material for the manufacture of not only cutlery and utensils. It has found application in the production decorative ornaments for room interiors.

The most famous alloy of silver and copper is sterling. It contains 92.5% precious metal and only 7.5% copper. It is the 925th test that is most in demand in jewelry. Most of all precious jewelry is made from it. Dazzling sterling is similar in color to pure silver, but has greater hardness and resistance to blackening.

For the production of jewelry, metal of the 960th sample is also used. However, such jewelry must be worn very carefully and take care of them. Due to the ductility of the metal, the products do not differ in durability.

Only 1% of the golden-pink metal contains 999 silver. Despite the short period of operation, such jewelry is willingly bought by residents of Japan. They believe that pure silver is closely associated with the Moon, which is the abode of deities merciful to people, and through the wearing of this precious metal they want to be closer to them.

What can be confused with ligatures?

Often they try to fake silver alloys, replacing them with similar-looking materials. The most common of these are copper alloys cupronickel and nickel silver. Melchior was very famous in antiquity under the name "Warsaw silver". Pendants, bracelets were made from it, guns and daggers were wrapped around them. Top material covered thin layer silver, so it was no different from real metal. It was much cheaper, and not only rich people could purchase products from it.

Nickel silver contains copper, nickel and zinc. In color and brilliance, it is so similar to the precious metal that it is even called the "new silver". Today, nickel silver is used in jewelry for the production of clasps and pins for jewelry, but numerous scammers can make rings and brooches from it and cupronickel to sell to gullible buyers at the price of precious metal. Often there are no samples on such products, which should already lead to thoughts about the dubious quality of jewelry. Therefore, it is better not to chase after a rather cheap "silver", but to buy it in jewelry stores.

What is good about Shibuichi alloy?

In addition to the generally recognized tested ligatures, there are silver compounds containing a high percentage of copper (from 30 to 75). They are not of great value jewelry market, but are used in the manufacture interesting jewelry. One such alloy is shibuichi. It is also called “Japanese bronze” in another way, since it was invented by the Japanese, who used ligature everywhere in the production of handles for daggers and knives. Now beautiful brooches, bracelets, rings and earrings are made from shibuichi.

The word shibuichi means "three quarters" because it contains ¾ copper and only ¼ silver. natural flowers of this alloy are pale pink and yellowish white. The beauty of "Japanese bronze" is that when patinated, the material takes on a variety of shades from light gray to chocolate brown. Thanks to them, the products look unusual and fantastically beautiful. Whatever alloy of silver men and women choose for themselves, they can be sure that the products will delight them with their appearance and brilliance for a long time.

Silver has been known to mankind since ancient times, but continues to be in demand at the present time. Its physical properties differ sharply from all other noble metals.

Silver is very ductile, lends itself well to forging and is extremely malleable. The degree of softness is lower than that of gold, but higher than copper. The metal has the highest electrical and thermal conductivity, excellent reflectivity, does not react with other metals and is perfectly polished.

Jewelers have been using silver to make jewelry for a long time. However, it is not used in its pure form. Due to its softness, the product is easily deformed, scratched and loses the clarity of embossed patterns. Silver is afraid of hydrogen sulfide and ozone and quickly darkens, becoming covered with a black hard-to-remove coating. To enhance the strength characteristics, silver is combined with some metals: copper, aluminum, cadmium, nickel, zinc and rhodium. Such additives are called ligatures.

They give silver hardness and wear resistance. Jewelers make highly artistic products from metal with the obtained qualities. sophisticated technology execution.

To estimate the silver content in an alloy, use the sign try, which shows how many grams of silver are contained in one kilogram of the alloy. The most known to the general consumer are 875, 925, 960 and 999 samples.

When alloyed with multiple metals, a more sophisticated technology is used. So, to obtain an alloy of silver-copper-zinc-cadmium, each metal is pre-rolled into the thinnest plates. Then these plates are wrapped in silver sheets, packaged, pressed, beaten and melted.

However, the introduction of an inappropriate amount of ligature into silver, the alloy may not improve the properties of silver, but sharply worsen it. For example, when 1% nickel is introduced into the alloy, its strength increases, and already at 2.6%, the alloy becomes brittle. If more than 9% tin is added to an alloy of silver and copper, then such an alloy will turn out to be brittle, it will begin to melt and oxidize.

To avoid such problems, jewelers add to silver the most suitable metal - copper. Usual norm the introduction of copper is from 5 to 50%. Products have fine appearance and are similar to pure metal.

Alloy shibuichi , obtained in Japan, consists of only ¼ of silver, and ¾ is copper. An alloy with the addition of 5% gold also has the same name. The alloy is very popular at present. Products are usually patinated to give beautiful shades. Widely applicable in the manufacture of bracelets, knife handles, rings, earrings and brooches.

In Russia, metal alloys are regulated by GOST. According to him, silver has a short designation - Cp, gold - Zl, palladium - Pd, copper - M.

Alloy of silver and copper, formulas a its easy to read and understandable for its simplicity.

So the ZlSrM585-80 alloy (called red gold) contains 585 parts of gold, 80 parts of silver, the remaining parts are copper (1000-585-80=335). That is, an alloy ingot of this brand weighing 100 grams contains 58.5 g of gold, 8 g. silver and 33.5 g of copper.

The most famous and widely used alloys: Ag 960, Ag 925, Ag 875, Ag 830, Ag 800

• It is also worth noting the so-called technical silver alloy

Silver grade metal is contained from 49.5 to 50.5%. Iron not more than 0.13%, lead - 0.005%, antimony and bismuth - 0.002% each. The rest is copper.

However, to protect silver from exposure environment electroplated coatings are also used by rhodium plating, nickel plating or layering clear varnish. When long-term storage the product is passivated with wax.

Silver (CAS number: 7440-22-4) is a ductile silver-white precious metal. It is designated by the symbol Ag (lat. Argentum). Silver, like gold, is considered a rare precious metal. However, of the noble metals, it is the most widely distributed in nature.

According to the periodic system of chemical elements of D. I. Mendeleev, silver belongs to the 11th group (according to the outdated classification - a side subgroup of the first group), the fifth period, with atomic number 47.

Silver derives its name from the Sanskrit word "argenta", which means "bright". From the word argenta came the Latin "argentum". light shine silver is somewhat reminiscent of the light of the moon, therefore, in the alchemical period of the development of chemistry, it was often associated with the moon and was designated by the sign of the moon.

The facts of finding huge silver nuggets are known and documented. So, for example, in 1477, a silver nugget weighing 20 tons was discovered at the St. George mine. In Denmark, in the Museum of Copenhagen, there is a nugget weighing 254 kg, discovered in 1666 in the Norwegian mine Kongsberg. The vein-native silver formation, discovered in Canada in 1892, was a slab 30 meters long and weighing 120 tons. However, it should be noted that silver is chemically more active than gold, and therefore is less common in its native form.

Silver deposits are divided into proper silver ores (silver content above 50%) and complex polymetallic ores of non-ferrous and heavy metals (silver content up to 10-15%). Complex deposits provide 80% of its production. The main deposits of such ores are concentrated in Mexico, Canada, Australia, Peru, the USA, Bolivia and Japan.

Physical properties of silver

Natural silver consists of two stable isotopes 107Ag (51.839%) and 109Ag (48.161%); more than 35 radioactive isotopes and isomers of silver are also known, of which 110Ag is practically important (T half-life = 253 days).

Silver is an extremely malleable metal. It is well polished, giving the metal a special brightness, cut, twisted. By rolling, sheets up to 0.00025 mm thick can be obtained. From 30 grams, you can draw a wire more than 50 kilometers long. Thin silver foil in transmitted light has purple. In its softness, this metal occupies an intermediate position between gold and copper.

Silver is a white shiny metal, with a cubic face-centered lattice, a = 0.4086 nm.
Density 10.491 g/cm3.
Melting point 961.93°C.
Boiling point 2167°C.
Silver has the highest electrical conductivity among metals, 6297 sim/m (62.97 ohm-1 cm-1) at 25°C.
Thermal conductivity 407.79 W / (m K.) at 18 ° C.
Specific heat capacity 234.46 j/(kg K).
Electrical resistivity 15.9 nom m (1.59 microhm cm) at 20 °C.
Silver is diamagnetic with an atomic magnetic susceptibility at room temperature -21,56 10-6.
Modulus of elasticity 76480 MN/m2 (7648 kgf/mm2).
Tensile strength 100 MN/m2 (10 kgf/mm2).
Brinell hardness 250 Mn/m2(25 kgf/mm2).
The configuration of the outer electrons of the Ag atom is 4d105s1.
The degree of reflection of silver in the infrared range is 98%, and in the visible region of the spectrum - 95%.
Easily alloys with many metals; small additions of copper make it harder, suitable for the manufacture of various products.

Chemical properties of silver

Pure silver is stable in air at room temperature, but only if the air is clean. If the air contains at least a small percentage of hydrogen sulfide or other volatile compounds sulfur, the silver darkens.
4Ag + O2 + 2H2S = 2Ag2S + 2H2O

When heated to 170°C, its surface is covered with an Ag2O film. Ozone in the presence of moisture oxidizes silver to higher oxides AgO or Ag2O3.

Silver dissolves in concentrated nitric and sulfuric acids:
3Ag + 4HNO3 (30%) = 3AgNO3 + NO + 2H2O.
2Ag + 2H2SO4 (conc.) = Ag2SO4 + SO2 + 2H2O.
Silver does not dissolve in aqua regia due to the formation of a protective AgCl film. In the absence of oxidizing agents, normal temperatureНCl, HBr, HI also do not interact with it due to the formation of a protective film of poorly soluble halides on the metal surface.

Ag dissolves in ferric chloride, which is used for etching:
Ag + FeCl3 = AgCl + FeCl2
It also dissolves easily in mercury, forming an amalgam (a liquid alloy of mercury and silver).
Free halogens easily oxidize Ag to halides:
2Ag + I2 = 2AgI
However, this reaction is reversed in the light, and silver halides (except fluoride) gradually decompose.

When alkali is added to solutions of silver salts, Ag2O oxide precipitates, since AgOH hydroxide is unstable and decomposes into oxide and water:
2AgNO3 + 2NaOH = Ag2O + 2NaNO3 + H2O
When heated, Ag2O oxide decomposes into simple substances:
2Ag2O = 4Ag + O2-
Ag2O reacts with hydrogen peroxide at room temperature:
Ag2O + H2O2 = 2Ag + H2O + O2.

Silver does not directly interact with hydrogen, nitrogen and carbon. Phosphorus acts on it only at a temperature of red heat with the formation of phosphides. When heated with sulfur, Ag easily forms Ag2S sulfide.

Biological properties of silver

Silver enters the human body with water and food in negligible amounts - about 7 micrograms per day. Such a phenomenon as a deficiency of silver has not yet been described anywhere. None of the serious scientific sources classifies silver as a vital bioelement. In the human body, the total content of this noble metal is a few tenths of a gram. Physiological role its unclear.

It is believed that small amounts of silver are useful for the human body, large amounts are dangerous. With many years of work with silver and its salts, when they enter the body for a long time, but in small doses, an unusual disease can develop - argyria. Silver entering the body, accumulating in the skin and mucous membranes, gives them a gray-green or bluish color.

Argyria develops very slowly, its first signs appear after 2-4 years continuous work with silver, and a strong darkening of the skin is observed only after decades. Once appeared, argyria does not disappear, and it is not possible to return the skin to its previous color. A patient with argyria may not experience any pain or health disorders. With argyria, there are no infectious diseases: silver kills all pathogenic bacteria that enter the body.

Silver compounds are toxic. When large doses of its soluble salts enter the body, acute poisoning occurs, accompanied by mucosal necrosis. gastrointestinal tract. First aid in case of poisoning is gastric lavage with a solution of sodium chloride NaCl, while insoluble chloride AgCl is formed, which is excreted from the body.

Silver is bactericidal; at 40-200 µg/l, non-spore bacteria die, and at more high concentrations- controversial. According to the current Russian sanitary standards silver is a highly hazardous substance and its maximum allowable concentration in drinking water is 0.05 mg/l.

The magical properties of silver

In the Middle Ages, silver was endowed with mystical features, the ability to protect against evil forces, in particular, from demons and vampires, and heal from ailments. If silver darkened on a person, then illness was predicted to him.

It was believed that this pure “lunar” (silver has always been associated with the Moon) metal has the ability to heal diseases, rejuvenate, and absorb everything negative.

Advances in science have proven that the bactericidal properties of silver actually improve health and speed up recovery, and the darkening of this metal indicates a strong change in the acid-base balance in the human body, which is a sign of ill health.

In the common European tradition, silver is a "feminine" metal, as opposed to "masculine" and energetic, sunny gold. Gold is a symbol of power, silver is wisdom.

History of silver

Silver has been known to mankind since ancient times. This is due to the fact that in those days it was often found in native form - it did not have to be smelted from ores.
It is believed that the first deposits of silver were in Syria, from where the metal was brought to Egypt.
In the VI - V centuries BC. e. the center of silver mining moved to the Lavrian mines in Greece.
In IV - I centuries BC. e. Spain and Carthage were the leaders in the production of silver.
In the II - XIII centuries, many mines operated throughout Europe, which were gradually depleted.

The development of America led to the discovery of the richest silver deposits in the Cordillera. Mexico is the main source.

In Russia, the first silver was smelted in July 1687 by the Russian ore explorer Lavrenty Neygart from the ores of the Argun deposit. In 1701, the first silver smelter was built in Transbaikalia, which began to smelt silver on a permanent basis 3 years later.

Silver mining

Today in Russia 550 - 600 tons of silver are mined annually. This is not much: 50 times more precious metal is mined in Peru; Mexico, Chile and China left not far from Peru. On a global scale, the annual production of silver is estimated at twenty thousand tons. The explored reserves of silver do not exceed 600 thousand tons.

Getting Silver

Currently, cyanide leaching is used to obtain silver. In this case, its water-soluble complex cyanides are formed:
Ag2S + 4NaCN = 2Na + Na2S.
To shift the balance to the right, air is passed through it. Sulfide ions are oxidized to thiosulfate ions (S2O32– ions) and sulfate ions (SO42– ions).
Ag cyanide solution is isolated with zinc dust:
2Na + Zn = Na2 + 2Ag.
To obtain silver of very high purity (99.999%), it is subjected to electrochemical refining in nitric acid or dissolved in concentrated sulfuric acid. In this case, silver goes into solution in the form of sulfate Ag2SO4. The addition of copper or iron causes the precipitation of metallic silver:
Ag2SO4 + Cu = 2Ag + CuSO4.

SILVER ALLOYS

According to the Decree of the Government of the Russian Federation "On the procedure for approbation and branding of products from precious metals"The following samples of silver alloys were accepted: 999, 960, 925, 916, 875, 800 and 720.

The sample of silver means the ratio of precious metal and ligature. A ligature is a metal that is added to an alloy of silver to improve its physical properties. Copper is most often used as such a ligature, but other metals can also be used: nickel, cadmium, aluminum and zinc.

To determine the ratio of silver and ligature in Russia and a number of European countries, the metric system has been adopted, which determines the ratio of silver to 1000 alloy units. According to this system, a 925 silver sample means that there are 925 units of this noble metal per 1000 units of the alloy, or in other words, 925 grams of pure silver will be in 1 kg of the alloy.
An example of marking a silver product: CPM 925 (an alloy of 92.5% silver and 7.5% copper).

The purest 999 sterling silver is used only for the manufacture of ingots and silver collectible coins, since pure silver is an extremely soft metal that is unsuitable even for making jewelry.

960 silver alloy. In terms of quality and mechanical properties, it practically does not differ from pure silver. It is used in jewelry for the manufacture of thin, highly artistic products.

925 sterling silver alloy is also called "standard silver". Has a noble silver - White color and high anti-corrosion and mechanical properties. It is widely used in jewelry for the manufacture of various ornaments.

Alloy 916 is deservedly considered a good silverware. It is this alloy that is used to make sets decorated with enamel or gilding.

An alloy of 875 silver is used in the industrial manufacture of jewelry. Due to the high hardness, it is more difficult than previous alloys to be machined.

An 830 silver alloy differs from the previous one only in the percentage of silver content - at least 83%. In terms of technical, mechanical qualities and scope of application, it slightly differs from 875 samples.

800 silver alloy. Cheaper than the described alloys, has a noticeable yellowish color and low air resistance. The ductility of this alloy is much lower than that of the above. From positive qualities it should be noted high casting properties, which makes it possible to use it for the manufacture of cutlery.

720 silver alloy. It has many negative properties: refractoriness, bright yellowish color, low ductility, hardness. Used only in industry.

APPLICATION OF SILVER

Thanks to their unique properties: high degrees electrical and thermal conductivity, reflectivity, light sensitivity, etc. - silver has a very wide range of applications. It is used in electronics, electrical engineering, jewelry, photography, precision instrumentation, rocket science, medicine, for protective and decorative coatings, for the manufacture of coins, medals and other commemorative items. The scope of silver is constantly expanding, and its application is not only alloys, but also chemical compounds.

Currently, about 35% of all silver produced is spent on the production of film and photographic materials.
20% in the form of alloys is used for the manufacture of contacts, solders, conductive layers in electrical engineering and electronics.
20 - 25% of the produced silver is used for the production of silver-zinc batteries.
The rest of the noble metal is used in jewelry and other industries.

The use of silver in industry

Silver has the highest electrical conductivity, thermal conductivity and resistance to oxygen oxidation at normal conditions. Therefore, it is widely used for contacts of electrical products, for example, relay contacts, lamellas, as well as for multilayer ceramic capacitors, in microwave technology as a coating of the inner surface of waveguides.

Copper-silver solders PSR-72, PSr-45 and others are used for soldering a variety of critical compounds, including dissimilar metals.

A large amount of silver is constantly consumed for the production of silver-zinc and silver-cadmium batteries, which have a very high energy density and mass energy intensity and are capable of delivering very high currents to the load with low internal resistance.

Silver halides and silver nitrate are used in photography because of their high light sensitivity.
Silver iodide is used for climate control ("cloud dispersal").

Used as a coating for highly reflective mirrors (normal mirrors use aluminum).

Silver is used as an additive (0.1-0.4%) to lead for casting current collectors of positive plates of special lead batteries (very long term service (up to 10-12 years) and low internal resistance).

As a catalyst in oxidation reactions, for example in the production of formaldehyde from methanol, as well as epoxide from ethylene.

Silver chloride is used in chlorine-silver-zinc batteries, as well as coatings on some radar surfaces. In addition, silver chloride, which is transparent in the infrared region of the spectrum, is used in infrared optics.

It is used as a catalyst in gas mask filters.

Silver phosphate is used to melt special glass used for radiation dosimetry. The approximate composition of such glass: aluminum phosphate - 42%, barium phosphate - 25%, potassium phosphate - 25%, silver phosphate - 8%.

Silver fluoride single crystals are used to generate laser radiation with a wavelength of 0.193 μm (ultraviolet radiation).

Silver acetylenide (carbide) is occasionally used as a powerful initiating explosive (detonators).

Silver permanganate, crystalline dark purple powder, soluble in water; used in gas masks. In some special cases, silver is also used in dry galvanic cells of the following systems: chlorine-silver cell, bromine-silver cell, iodine-silver cell.

The use of silver in medicine

It is used as a disinfectant, mainly for water disinfection. Limited use in the form of salts (silver nitrate) and colloidal solutions(protargol and collargol) as an astringent.
Silver is registered as food additive E174.
For small wounds, abrasions and burns, bactericidal paper impregnated with silver nitrate and chloride is used.
Silver promotes the resorption of tumors, activates the process of restoration of organs after an illness.
Silver plates applied to the area of ​​the large intestine activate its work and improve peristalsis.

The use of silver in the jewelry industry

Silver has been known as a jewelry material for more than six millennia. Argentum is the whitest of the precious metals, and this quality is actively used in the creation of jewelry. Neutral color This metal goes well with black, which is natural for it - when oxidized, silver darkens, and the combination of white and blackened silver is very effective. This is also the material for thin, delicate classic jewelry, and for traditional filigree items, for large ethnic bracelets and rings, and for ultra-modern design novelties. Silver holds its shape best traditional art, while serving as a material and testing ground for bold creative experiments. Silver is a material in which large jewelry in national style look the most impressive.

Silver jewelry is a sign of taste, the perfect complement to any suit, both formal and informal. They look great both on their own and in an alloy with gold or platinum. The discreet nobility that distinguishes silver jewelry is perfectly emphasized by blotches. precious stones, be it turquoise, topaz or sapphire.

INVESTING IN SILVER

This precious metal is often used as a way to invest. Investors use silver to diversify risks, but trading contracts for it requires a lot of investment.

Silver can be bought in the bank in the form of precious ingots different weight. It is best to store bullion in a bank by renting a separate cell. Thus, you will not overpay tax. Investing in silver through the purchase of bullion is attractive in the sense that you can feel like a real owner of the precious metal. It is this way of investing in silver that is recommended by those who are confident in active growth prices for this metal investors.

Investment coins can also be bought at banks. Do not confuse ordinary collectible coins with investment ones. Collectible coins have a greatly inflated price, which is far from real price on metal. Investment coins are created specifically for the purpose of investing in precious metals. It is also better not to take them from the bank, but to put them in a cell.

OMS - depersonalized metal account, in relation to costs, the most attractive way investing in silver. Here you have to pay only taxes on profits after the sale. Main disadvantage is that such accounts are not always backed by real metal, and banks can set any prices that are far from the real state of affairs in the precious metals market, especially if the price of silver jumps sharply upwards (which is possible, according to some analysts).

Another attractive way to make a profitable investment is to buy shares of silver mining companies.

You don't need to invest in silver jewelry unless it's a work of art. The price of these decorations is very high, and you can only sell them at the price of scrap.

Obtaining surfaces with desired properties can be carried out by electrochemical separation of alloys from two or more metals under conditions of joint discharge of ions. Electrolytic deposition of alloys every year becomes more and more important for various fields of technology. Alloy coatings are often significantly more efficient than the production of parts from metallurgical alloys. Electrolytic alloys have slightly different properties than cast alloys. Their increased hardness, in particular, may have great importance for products operating under conditions of mechanical wear.

The corrosion resistance of electrolytic alloys often turns out to be higher than that of pure metals due to the special structure of alloy deposits.

Silver plating is one of the common types of coatings. Of the precious metals, it has received the widest application in electroplating. The reasons for such a widespread use of this metal are its properties: silver is easily polished, has high thermal and electrical conductivity, is characterized by high chemical resistance, and high (up to 95%) reflectivity.

But silver also has a number of significant drawbacks: low hardness (60-85 kg / mm 2) and wear resistance, as well as a tendency to tarnish over time, especially in an atmosphere of industrial gases. The chemical activity of silver coatings is especially high in the presence of a matte, unpolished surface.

The galvanic deposition of silver alloys opens up the prospect of obtaining coatings with the qualities required for the jewelry industry (high wear resistance and hardness), as well as brilliant alloys with increased weather resistance compared to ordinary matte silver.

Promising contact materials, as well as materials that can be widely used in the jewelry industry, are alloys of silver with antimony, nickel, palladium, cobalt, bismuth, and copper.

Silver alloys with lead, indium and thallium are used as anti-friction coatings.

Joint precipitation of metals makes it possible to isolate such metals into an alloy, which cannot be obtained in pure form from solutions. Electrolytes have been developed for the deposition of alloys based on refractory metals, in particular, alloys of silver with tungsten and molybdenum.

It is known that for the joint discharge of two types of ions, a certain ratio of ion activities in the electrolyte, metal activities in the alloy, and overvoltages under conditions of their joint release is necessary.

The standard potentials of metals, the joint deposition of which on the cathode is of practical interest, may differ by more than 2 volts.

Most effective way changes in the activity of ions is their binding into complexes. In this case, both a change in the activity of ions in a solution and a change in the kinetic conditions of their discharge occur, i.e., the equilibrium part of the potential and the polarization value change.

According to some researchers, the deposition of metals from complex electrolytes occurs by discharging free metal ions at the cathode, which are formed during the dissociation of complex ions. Due to the very low concentration of such ions, a significant concentration polarization occurs.

Other researchers believe that the complex ions themselves adsorbed on the cathode surface take a direct part in the discharge process. The reduction of these ions proceeds at more high energy activation, which causes a greater chemical polarization.

The flow of the process according to the first mechanism is possible in the case when the complex ions are not strong enough.

In addition, the discharge of simple ions can also occur at the beginning of the process, at low current densities. With an increase in the rate of the process upon reaching the discharge potential of complex ions, the process proceeds with chemical polarization.

E. I. Ahumov and B. L. Rozen derived an equation showing that at a constant current density, a linear relationship should exist between the logarithm of the ratio of the metal content in the alloy and the logarithm of the ratio of the concentrations of their ions in the electrolyte:

Consequently, necessary condition during the deposition of alloys, the composition of the electrolyte is constant, as well as the pH of the electrolyte, the change of which affects the composition of the cathode deposit (alloy).

Since the phase structure of alloys in to a large extent defines them physiochemical properties, it is of particular interest to study the causes causing education of certain phases during the electrocrystallization of alloys.

Analyzing the available literature, we can conclude that this issue has not yet been fully considered, often the range of compositions of the obtained alloys is very narrow, which does not allow us to reveal the existence of distinct dependencies.

The most interesting in terms of their physical and mechanical properties are alloys that form supersaturated solid solutions under the conditions of electrodeposition.

The formation of solid solutions occurs on the basis of a more noble component (in particular, silver) as a solvent, supersaturation usually does not exceed 10-12%.

In accordance with the regularity of N. S. Kurnakov, in alloys that form solid solutions, a sharp increase in hardness is observed.

For coating with silver and its alloys, only solutions of complex salts are used, with the exception of an electrolyte to obtain a silver-selenium alloy.

At present, twenty-three electrolytic silver alloys have been obtained (Table 1), and only ten of them are from non-cyanide electrolytes [30].

Table 1

In industry for silvering, almost exclusively cyanide electrolytes are used, known for 140 years and during this time not subjected to any fundamental changes.

Cyanic silver plating electrolytes are characterized by high scattering power, ~ 100% current efficiency; the precipitates obtained from them have a fine crystalline structure.

The main disadvantages of cyanide electrolytes include: the complexity of their preparation, lack of stability, low performance, and high toxicity.

In connection with the shortcomings listed above, one of the most important tasks of modern electroplating is the replacement of cyanide electrolytes with non-toxic ones, as well as the intensification of silvering processes. In addition, the problem of obtaining shiny coatings that do not fade with time has not yet been practically solved.

Let us consider in more detail some electrolytes (see Table 2) for the production of silver alloys.

Alloys obtained from pyrophosphate electrolyte have high microhardness (230 kg/mm2), their wear resistance is 15 times higher than that of pure silver. The coating has sufficient adhesion to steel even without the use of an undercoat. Comparative data of alloys obtained from pyrophosphate and cyanide electrolytes indicate that the properties of the alloy obtained from cyanide electrolyte are somewhat worse.

table 2

No. p / p	Electrolyte composition, g/l		Electrolysis mode, D to, a / dm 2, o C, etc.	Alloy composition (wt.% alloying component)	Hardness, kg / mm 2	Literary reference
	Components	Contents g/l
1	Ag (met.) Cu (met.) K 4 P 2 O 7 (free) pH	6 - 7 14 - 15 100 11 - 13	D to \u003d 0.5 - 0.7 t = 20 o C ηr = 95%	up to 15%	230
2	Ag (met.) Cu (met.) Trilon B NH 4 OH for pH	1 - 6 10 - 12 120 - 140 8 - 9	D to \u003d 0.5 - 1.5 t room η r = 50%	-	230
3	Ag (met.) Cu (met.) Trilon B KOH for pH	1,7 - 5,4 17 - 20,8 100 - 120 8,5 - 9,5	D to \u003d 0.5 D to \u003d 3.0 t room η r = 45 - 50%	15% 82% 60 - 70%	Max- 230
4	AgSCN NiSO4.7H2O Na 2 SO 4 .10H 2 O	1 - 50 8 - 12 100	D to \u003d 1.2 ma / cm 2 t=60 - 70 o C	4 - 20%	-
5	Σ(Ag + Ni) K 4 P 2 O 7	6 150	D to \u003d 0.4 - 0.5 t=18 - 25 η r = 60-70%	Alloys obtained in a wide range	180 (20% at. Ni) 480 (80-86% at. Ni)
6	Pd (met.) Ag (met.) Trilon B (NH 4) 2 CO 3 NH 3 (free) pH	0.15-0.20 mol/l 0,02 - 0,03 0,12 - 0,20 0,1 - 0,20 0,25 - 0,50 9,0 - 9,5	D to \u003d 0.07 - 0.15 D to \u003d 0.3 - 0.5 t= 20 - 40 ηr = 90-95%	15-25% 40 - 50%	220 - 280
7	Ag (met.) Pd (met.) K 4 P 2 O 7 KCNS	0 - 14 10 - 17 20 - 70 130 - 180	D to \u003d 0.4 - 0.5 t = 18-20	2 - 8%	-
8	AgSCN K 2 Pd(CNS) 4 KCNS	0.1M 0.1M 2M	-	-	-
9	Ag (met.) Pt (met.) LiCl HCl (acid)	3,4 5,1 500 10	D to \u003d 0.2 - 0.25 t = 70°C ηr = 20-80%	0 - 60	150-350%
10	AgNO3 K2WO4 (NH 4) 2 SO 4 (CHOH . CO 2 H) pH	35 30 150 12 8 - 10	D c \u003d 0.8 ηr = 106%	up to 2% wt.	H v is 1.5-2 times more than pure silver electrolyte
11	Ag (met.) KCN (free) K2CO3 Sb 2 O 3 (powder) KNaC4H4O6. 4H2O	40 - 50 50 - 60 up to 70 20 - 100 20 - 40	D c \u003d 0.7 -0.8 t = 20 ± 4	0,5 - 0,6%	130 - 140 kgf/mm 2
12	Ag (met.) Sb (met.) K 4 / \u003d 2.5 - 0.5	1 n. 1 mmol/l 5 mmol/l 8 ml/l	D c \u003d D a \u003d 2 - 6 ma / cm 2 t=20	0.13 - 4.5 at.%	-
14	Ag (met.) Bi (met.) K 4 P 2 O 7 (free) KCNS (free) K 4). Increasing the current density by 1 a/dm 2 increases the percentage of antimony in the sediment by 0.5%. The use of a current density greater than 1 a/dm 2 is possible with stirring and an electrolyte temperature of 50-60 o C, which is highly undesirable if the electrolyte has a relatively high concentration of free potassium cyanide. N. P. Fedotiev, P. M. Vyacheslavov and G. K. Burkat proposed a non-cyanide electrolyte for the deposition of a silver-antimony alloy with an antimony content of 2-2.5%. This electrolyte is based on silver plating synerhosistorhodium electrolyte. The alloy is a series of solid solutions, the presence of intermetallic compounds of the composition AgSb and Ag 3 Sb is noted in it. When the content of antimony in the sediment was 8-10%, mirror-shiny sediments were obtained. Calcium thiocyanate is used as an anode depassivator. The anode current density should not be less than the cathodic one, otherwise chemical dissolution of the anodes will occur. The properties of the alloy are not much different from the properties of an alloy obtained from a cyanide electrolyte. This electrolyte is much less toxic than that described above. From solutions containing 20 - 30 mmol / l H 2 SeO 3, 2.5--10 mmol / l AgNO 3, acidified depending on the concentration of AgNO 3 15 - 60 ml / l nitric acid, compact precipitates of the silver-selenium alloy were obtained. The composition and quality of sediments depend on the ratio of H 2 SeO 3 and AgNO 3 in catholic, their total concentration, temperature, and current density. On a silver cathode, compact shiny deposits were obtained, up to 1 μm thick, with a composition from 0.13 to 4.5 at.% selenium; on a platinum cathode, only opaque deposits of composition from 2.4 to 4.4 at.% selenium were obtained. Thin layers of an alloy of selenium with silver have semiconductor properties. The experiments were carried out in a Plexiglas vessel with a PVC fabric diaphragm and platinum anodes; platinum plate or copper (sometimes platinum), electrolytically coated with silver, served as cathodes. The results of the work are very interesting, since this is the first incomplete electrolyte for the production of silver alloys, but the production of an alloy of silver with selenium is still in the laboratory development stage. For the deposition of an alloy of silver - bismuth with 1.5 - 2.5 wt% of bismuth, a pyrophosphate-cyanogen electrolyte is proposed. The alloy has a high microhardness (190 kg / mm 2), its wear resistance is 3-4 times higher than that of pure silver. With the joint deposition of silver and bismuth, the discharge of both components of the alloy is depolarized, and the limiting currents of the discharge of silver and bismuth into the alloy increase. Bismuth precipitates into the alloy with the formation of a solid solution of bismuth in silver up to 1.3 - 1.5 at.% (compared to 0.33 at% bismuth at temperatures above 200 o C according to the phase diagram) The electrolyte for obtaining the alloy was prepared on the basis of a ferrous and hierogen electrolyte by adding a bismuth pyrophosphate complex (КВiP 2 О 7) to it. The electrolyte is sensitive to the NO - 3 ion, therefore, the ferrous-cyanide silver plating electrolyte was prepared from silver chloride, which, of course, is quite complicated. Sediments of satisfactory quality were obtained in a very small range of electrolyte pH from 8.3 to 8.7. In the literature, there are references to the possibility of deposition of a silver-bismuth alloy from a complex ammonium sulfate sulfosalicylate electrolyte, but the authors do not provide specific data on the composition of the electrolyte and the composition of the precipitates. Of all the above electrolytes, only the pyrophosphate-thiocyanate electrolyte has so far found wide industrial application for the preparation of a silver-palladium alloy (Table 2). In the literature, the issues of obtaining mirror-shiny silver alloys, and especially from non-cyanide electrolytes, are still insufficiently covered, although it is precisely such coatings that are of increased interest due to their excellent decorative look and improved corrosion resistance. The combination of both these qualities is especially valuable for the jewelry industry. The challenge is to develop sufficiently fast non-toxic electrolytes for the deposition of shiny silver alloys. LITERATURE 1. B. I. Skirstymoyaskaya, Chemistry Achievements. 33.4, 477 (1964). 2. Fedot'ev N. P., Bibikov N. N. Vyacheslavov P. M., Grilikhes S. Ya. Electrolytic alloys. Mashgiz, 1962. 3. Zytner L. A. Dissertation (PhD). LTI them. Lensoveta, 1967. 4. Yampolsky AM Electrolytic deposition of noble and rare metals. "Engineering", 1971. 6. Melnikov P. S., Saifullin R. S., Vozdvizhensky G. S. Protection of metals, vol. 7, 1971. 7. Patent of Germany, from the 23rd century. 8. Burkat G. K., Fedotiev N. P., Vyacheslavov P. M. ZhPKh, XLI, vol. 2, 427, 1968. 9. Kudryavtsev N. T., Kushevich I. F., Zhandarova I. A. Protection of metals, 7, 2, 206, 1971 10. Agaroniyants A. R., Kramer B. Sh. et al. Electrolytic coatings in instrumentation. L., 1971. 11. G. K. Burkat, N. P. Fedotiev, et al. 13. Vyacheslavov P. M., Grilikhes S. Ya. et al. Electroplating of noble and rare metals. "Engineering", 1970. 14. Brenner A. Electrodeposition of Alloys, N.-J.-L., (1963) 15. Izbekova O. V., Kudra O. K., Gaevskaya L. V. Avt. certificate, USSR, class. 236 5/32, no. 293060, app. 10/X 1969. 16. Struiina T. P., Ivaiov A. F. et al. Electrolytic coatings in instrumentation. 83, L., 1971. 17. Kudryavtseva I. D., Popov S. Ya., Skalozubov M. F. Research in the field of electroplating (based on materials of the interuniversity scientific meeting on electrochemistry), 73, Novocherkassk, 1965 18. A. N. Frumkin, V. S. Bagotsky, Z. A. Iofa, and V. N. Kabanov, Kinetics of Electrode Processes. Ed. Moscow State University, 1952. 19. Vahramyan A. T. Electrodeposition of metals. Ed. Academy of Sciences of the USSR, 1950. 20. Kravtsov V.I. Electrode processes in solutions of metal complexes, Leningrad State University, 1959. 21. Le Blanc M., Jchick J. Z. phus. chem., 46, 213, 1903. 22. Levin. AI Abstracts of reports of the scientific and technical conference on the theory and practice of using non-toxic electrolytes in electroplating. Ed. Kazan University, 1963. 23. Andryushchenko F.K., Orekhova V.V., Pavlovskaya K.K. Pyrophosphate electrolytes. Kyiv "Technique", 1965. 24. E. I. Ahumov and B. L. Rosen, Doklady AN SSSR, 109, No. 6, 1149, 1956. 25. Burkat G. K. Dissertation (c. t. p.). LTP them. Leningrad City Council, 1966. 26. E. I. Patsauskas, I. V. Yaiitskyi, and I. A. Lasavichene, Tr. AN Lit. SSR, B., No. 2(65), 61 - 7!, 1971. 27. Kankaris V. A., Pivoryunaite I. Yu. Chemistry and chemical technology. Scientific works of universities Lit. SSR, No. 3, 1963. 29. Dubyago E. I., Tertyshnaya R. G., Osakovsky A. I. Chemical technology. Republican interved, tematmch. spider tech. Sat., issue. 18, 8, 1971 30. Krohn and Bohn C, W. Plating, 58, no. 3, 237-241, 1971. 32. Fantgof Zh. N., Fedotiev N. P., Vyacheslavov P. M. Coatings with precious and rare metals. Materials of the seminar, 105, M., 1968 33. Kudra O. K., Izbekova O. V., Gaevskaya L. V. Bulletin of the Kyiv Polytechnic Institute, No. 8, 1971. 34. Rozhkov G. A., Gudpn N. V. Proceedings of the Kazan Chemical-Technological Institute. in-ta, in. 36, 178, 1967. 35. Grilnkhes S. Ya., Isakova D. S. All-Union Scientific Conference. Ways of development and recent achievements in the field of applied electrochemistry (November 10-12, 1971), L., 1971. Counterfeiting silver began in ancient times, when it was valued even higher than pure gold. Today for this valuable white metal often give out various analogues and alloys. Most often, instead of silver, buyers are offered lead, zinc or aluminum. A professional can easily distinguish a fake from natural metal, but it’s hard for a simple layman to do this. In addition, many online stores and online flea markets are replete with products marked "silver." or "silver pl.". This only indicates that the item is silver plated and not made entirely of that metal. Over time, such products begin to lose their aesthetic appearance, blacken, become covered with plaque and lose information about the place of the sample and brand. If thorough cleaning only exacerbated these signs, then we can safely say that the product turned out to be a fake. You can distinguish silver from zinc using iodine. It is necessary to drop a drop of funds on the thing and leave the product for a while. Real silver will not enter into a chemical reaction with iodine, and zinc will show itself blue. In addition, a zinc product can leave unpleasant dark stripes and spots on your hands. Silver is very easy to confuse with cupronickel, which is an alloy of lead, nickel and copper. Very often cupronickel is included in the composition of the so-called technical silver. Before conducting any experiments with a thing, it is worth considering it more carefully. On cupronickel there will be no sample mark, but there will be a stamp "MNTs". If the inscription on the product cannot be deciphered, you can lower the water and observe a little. Cupronickel alloy will cause a light greenish tint to appear on the surface of the water. You can confirm your assumptions with lapis pencil. If the product begins to darken under its influence, then we can safely say that there is a cupronickel item in the hands. Less commonly, aluminum is given out as silver, although this metal has a slightly different color, luster and hardness. After several days of wear, such jewelry begins to deteriorate before our eyes. To distinguish a silver item from a fake, you need to arm yourself with a magnet: an aluminum item will instantly be attracted to it. Whatever alloy the chain, ring or box is made of, this can always be checked by slightly scratching the product with a needle. If there is a layer of dark brown metal under the coating, then we can only say that the thing was silver-plated. It also happens that it is necessary to distinguish silver from white gold. The first is often sold under the guise of expensive metal, treated with a decorative and protective coating of radium. In this case, it will be almost impossible for a non-professional to distinguish between these two metals at a glance. Here, the price of the product and its density will be of great importance. It is necessary to lower the jewelry into a beaker and weigh it for accurate scales. Then calculate the density and compare with the "correct" densities of metals. There is a more cardinal way to distinguish silver from white gold - to drip on the product hydrochloric acid. In this case, nothing will happen to gold, and silver will change its structure.