GOLD AND SILVER BUSINESS
Gold and silver are usually called the artistic processing of precious metals. Since ancient times, gold and silver have been used to create a variety of objects, not only because they are beautiful and durable, but also because these metals are relatively easy to process using a variety of techniques and can additionally be decorated with precious stones, colored enamel, etc. . The materials themselves indicate that the works of them were intended mainly for the elect: the tsar’s circle, church nobility, the decoration and life of palaces and monasteries.
By appointment, items made of precious metals are divided into precious utensils and jewelry. For the manufacture of products using gold, silver, platinum, as well as alloys.
Gold has been in use at all times and was one of the most expensive materials due to its color, luster, and also its physical and chemical properties: in air at high temperature it does not lose its qualities (its melting point is 1064 ° C) and it resists acids except chlorine-containing, it is soluble only in “aqua regia”, (a mixture of nitric and hydrochloric acids in the ratio 1/3), selenic acid, potassium cyanide and sodium. Gold is the most malleable metal: from 1 g of gold you can draw a wire of 3000 m.
Silver surpasses gold in malleability, flexibility and hardness, but in air (under the influence of atmospheric hydrogen sulfide and phosphorus), it is oxidized and covered with a dark brown patina, therefore they often resorted to gilding silver, thereby combining the best properties of both metals in one product : lightness and cheapness of silver, (it cost 12-14 times cheaper than gold), with durability and warm color of gold. Silver dissolves best in nitric acid, and its temperature is 960 ° C.
Alloys. Pure gold and silver are too soft to make products from, so they are often alloyed with other metals: gold with copper and silver, and silver with copper. The possible amount of other metals, in which the precious properties are not lost, is determined by the regulations. Additives affect the color of the alloy: when more copper and less silver is added to gold, red gold is obtained, and when the proportion is inverse, yellow gold is obtained. When nickel and palladium are added, white gold is obtained, and with cadmium, green gold is obtained.
The amount of metals added to gold and silver is indicated by the assay mark, and the content of precious metals in the alloy, starting from the 19th century, is given in thousandths: 1000/1000 – pure metal, it is too soft and inconvenient for art processing; most commonly used are gold 750/1000 and 585/1000, and silver 812/1000, 900/1000. The initial designation of the alloy content in gold was given in carats, and silver in lots. In this case, pure gold was 24 carats (in contrast to precious stones, not the weight is indicated, but the gold content in the alloy), and silver – 16 lots.
The approximate content of pure gold in the alloy is established using the so-called test feature: as a test stone, black siliceous shale is used, on the surface of which the test alloy is pressed with pressure. The color of the bar is then compared with the color of the bar from the assay needle on the ingot, the contents of which are precisely known. To obtain a more accurate result, special laboratory tests are needed. Silver is checked in a similar manner.
Platinum has been used in jewelry since the 19th century – this most expensive and noble metal was discovered in the 18th century. Its name – platina – diminutive and contemptuous, derived from the Iskan word plata – silver, and meaning “silver” in Russian. For a long time they did not find use for it, they simply threw it away. The discovery of the remarkable properties of platinum dramatically changed its attitude. Exceptional chemical resistance, refractoriness (melting point is 1773, 5 ° С), density (three times more iron) made platinum an indispensable metal.