Overview of silver white silver, has a special chemical properties, its value as early as the beginning of understanding for the people in 700 BC Mesopotamian period. Silver and gold have been the same as in history, as legal tender in many countries, has a financial reserve functions. First, silver overview Silver, with its special chemical properties, was recognized as early as the Mesopotamian period in 700 BC. Silver has historically been like gold, as the legal currency of many countries, with financial reserve functions, and has also served as an important means of payment internationally. China has a long history of using silver as a currency. As early as the Warring States period, silver was used as currency. Since the Tang and Song Dynasties, the silver standard system has been gradually established, and the Ming Dynasty has become the official currency. China’s silver standard has continued until the issuance of legal currency in 1935 and the abolition of the silver standard. The silver dollar is the main form of silver in China's history. In foreign countries, money has always been the most important use of silver. Over time, people's understanding and attention to silver has been significantly improved. Silver has been widely used in industry, photography, jewelry, equipment, and currency. After the founding of New China, the management of silver has gone through a long period of exploration. From the beginning of the "common purchase and marketing" policy to the liberalization of the silver market in 2000, China's silver production and demand have grown exponentially in just a few years, becoming one of the world's leading silver producers, consumers and exporters. At present, China's silver supply and demand relationship is characterized by a serious excess of production, which requires a large amount of exports each year to digest domestic silver production. At the same time, demand for silver has grown steadily in many areas, supporting the continued prosperity of the domestic silver market. Second, the physical and chemical properties of silver Silver (Ag) is a white, shiny metal. The melting point of 961.93 ° C, the boiling point of 2212 ° C, the density of 10.5 g / cm 3 (20 ° C), the heat of fusion is 11.30 kJ / mol, the heat of vaporization is 250.580 kJ / mol. The silver is soft and has a Mohs hardness of 3.25 degrees. It has good flexibility and ductility. Its ductility is second only to gold. It can be pressed into thin sheets and drawn into filaments. One gram of silver can be drawn into a filament of 1800 meters long and can be rolled into a silver foil with a thickness of 1/100,000 mm, which is the best conductive and thermally conductive metal. Silver is also very reflective to light, with a reflectivity of 91%. Silver is chemically inert, does not interact with oxygen, is permanently exposed to the air, and is hydrogen sulfide in the air, and the surface turns black, forming a black silver sulfide. At normal temperature, halogen can slowly combine with silver to form silver halide. Silver does not react with dilute hydrochloric acid, dilute sulfuric acid and alkali, but can react with highly oxidizing acids (concentrated nitric acid and concentrated hydrochloric acid). Silver does not cause toxicity to human body, but long-term exposure to silver metal and non-toxic silver compounds can cause silver stagnation. The content of silver in the earth's crust is very small, accounting for only 1 × 10 - 5%. There is a simple natural silver in nature, but it is mainly a compound state. Extract silver from silver cyanide employed, i.e., treated with dilute sodium sulphide, silver silver to soluble sodium cyanide, addition of zinc powder, reduced to silver. About 75% of the metallic silver comes from the anode mud in copper and lead smelting. It is treated with concentrated sulfuric acid and can be converted into silver sulfate, which is then reduced to metallic silver by copper. There is also a waste fixing solution containing more silver, which can be first precipitated into silver sulfide, and then replaced with zinc powder to obtain metallic silver. Further purification requires electrolytic refining. Third, the main use of silver Silver is used as a precious metal for industrial, photographic, and jewelry, silverware, and silver coins. The versatility of silver makes it an irreplaceable application in most industries, especially in high-tech industries that require high reliability, precision and safety. Silver has good electrical and thermal conductivity and is widely used in the electronics industry, especially in conductors, switches, contacts and fuses. Silver can also be used for thick film pastes, and meshed and crystalline silver can be used as a catalyst for chemical reactions. Silver compound silver halide for the production of photographic film. Silver nitrate is used for silver plating to make silver mirrors. Artificial rainfall for silver iodide. Silver jewellery and silverware have good reflectivity and can achieve high brightness after polishing. In addition to the role of decoration and beautification, ancient Chinese people also used silverware to test poisons. When a silver comes into contact with certain poisons, a chemical reaction occurs to form a compound whose color is different from the silvery white color of the silver, thereby judging whether or not the poison is contained. Silver coins used to be the legal currency of the silver standard countries and were popular. However, with the reform of the monetary system and the generation of credit currency, silver coins gradually withdrew from the circulation field. At present, the minted silver coins are mainly invested in silver coins and commemorative silver coins. In addition, silver ions and silver-containing compounds can kill or inhibit bacteria, viruses, algae and fungi, reacting like mercury and lead, but the principles behind it are still unresolved. Because it has the effect of fighting disease, it is also known as pro-biometal. 4. Classification and inspection of silver Silver is mainly found in silver ore, silver concentrate, crude silver and sterling silver products. (1) Silver ore The content of silver in nature is very low, and the average content in the earth's crust is 1×10-5%. According to the distribution of elements in the earth's crust, it is still a trace element, which is only about 20 to 30 times higher than the average of gold. Silver ore resources are independent silver mines and associated silver mines. Silver minerals are mainly in the form of sulfides. The industrial minerals of silver mainly include natural silver, silver-silver ore, sulphur-copper-silver ore, bismuth- silver ore, and brittle silver ore. Although silver has many industrial minerals, they are rarely integrated into individual silver deposits, usually distributed in polymetallic ore, copper ore and gold ore in a dispersed state. More than half of the silver production comes from the comprehensive recovery of polymetallic ore. All the determination methods in analytical chemistry have been applied to the determination of silver, including gravimetric method, titration method, photometric method, fluorescence method, chemical kinetic method, etc. Among them, the advantages of atomic absorption spectroscopy are most prominent. Atomic absorption spectrometry for the determination of silver sensitive, accurate, fast, simple, and less interference, therefore, has been widely used in the determination of silver in ore. (2) Silver concentrate Silver concentrate is an intermediate product in the production process of non-ferrous metals. It is determined that the grade of silver and the content of related elements play an important role in the transaction and production process of silver concentrate. Determination of the main elements other than silver, and gold, copper, arsenic, bismuth, lead, zinc, sulfur, aluminum and magnesium. At present, the determination of silver and gold content, mainly using the most classic fire test gold weight method, generally carry out secondary test gold recovery; determination of copper content, high content of iodometric method, low content of atomic absorption spectrometry Determination of lead and zinc, high content by EDTA titration, low content by atomic absorption spectrometry; determination of arsenic content by potassium bromate titration, low content by atomic fluorescence spectrometry; determination of sulfur content The barium sulfate gravimetric method and the combustion neutralization method are used; the determination of the barium content is mainly atomic fluorescence spectrometry; the determination of aluminum is carried out by photometry and EDTA titration; and the determination of magnesium is generally carried out by atomic absorption spectrometry. With the advancement and development of science and technology, advanced analytical testing methods and methods have been applied to the analysis and determination of silver concentrates, such as ICP-AES, ICP-MS and XRF. These test methods are also applicable to the inspection of crude silver and sterling silver. (three) crude silver Crude silver mainly refers to mineral silver with a silver content of 30% to 99.9%, smelting primary silver products, and recycled silver. Due to the wide range of crude silver, the variety and complexity of the product variety has been caused. The crude silver can be utilized directly in addition to the recycled silver products whose components are relatively uniform and of known quality, and others usually need to be refined and concentrated to integrate the corresponding valuable metal elements. The three main components of mineral silver, smelting primary silver, and recovered silver in crude silver have considerable complexity. In addition to various precious metal components coexisting with silver, they also contain a large amount of metals with recycled value. Metals, compounds, etc. In addition, because of the large span of its quality, there are silver concentrates, currency silver, etc., as well as various types of minerals and industrial intermediate products with relatively low quality. (4) sterling silver Pure silver refers to silver produced from various silver-containing raw materials and having a silver content of 99.90% to 99.99%. Sterling silver is mainly used in photography, chemical reagents, chemical materials, pharmaceuticals, electronics, decoration, jewelry and silver products, and also accounts for a large share of money manufacturing and souvenir operations. V. Silver investment As a member of precious metals, silver is more closely related to gold than other precious metals. The investment demand of silver has grown rapidly in recent years and has become a generally accepted investment product in the world. The trading varieties are also very rich, mainly including silver spot, futures, options, silver stocks, and silver EFT funds. In 2006, Barclays Global Investment Company issued the first silver EFT fund, each of which is equivalent to a silver asset worth 10 ounces (about 311 grams). Investors can participate in silver investment by purchasing ETF shares. That is to broaden the silver investment channel, but also increase the demand for silver, will have a long-term role in promoting silver prices, just as the gold EFT fund played an important role in the sharp rise in gold prices in recent years. According to the World Silver Association's 2009 Global Silver Survey, the main factor driving the silver price last year was the investment demand, and this momentum will continue. At present, the three silver ETFs in the international market (BGI of New York Barclays, BTG of London, ETFecurities of London and ZKB of Switzerland) have all increased significantly. The amount of Masukura has increased several times this year. The investment value of silver is undervalued for a long time, so there are more investment opportunities. Since China opened its silver market in 1999, it has gradually emerged a special silver market and exchange products. As people's interest in precious metals investment grows, their investment horizons continue to expand. For example, many investors have begun to pay attention to silver investment. Compared with the gold market, there are not many channels suitable for individual investment in silver, mainly the physical standard silver bars and the silver T+D business established by the gold exchange and commercial banks. In addition, silver coins are also the investment choice of many people, but because silver coins and commemorative gold coins are mainly based on their collection characteristics, they have a self-contained market category. In addition, due to the small value of the currency and the high craftsmanship, even if the investment type of silver coins is issued, it has a double premium, so it cannot be equated with silver investment. If silver is used as a long-term investment product, investors can choose investment-type standard silver bars with simple process, low premium level and repurchase channels. However, due to the low unit price of silver, the silver bar casting specifications are correspondingly large, and the physical collection is inconvenient. . If the same 1 million yuan investment gold bars, only about 4 kg, easy to save; while investing in silver ingots, as much as 250 kg, storage and transportation are problems. Therefore, the silver T+D spot deferred settlement business is currently the main investment channel. Need to remind investors that although the threshold for investing in silver is low, but because T+D business is a two-way margin trading, its flexibility and convenience are greatly improved, while the leverage effect of margin will simultaneously amplify the benefits and risks. It is more suitable for investors with certain investment technology and experience and strong risk tolerance. Since 2007, China's silver production has ranked first in the world and maintained steady growth. The consumer market also contains huge business opportunities. It is expected that by 2015 China will become the global silver jewelry trading center, which will be second only to the United States as a world-class silver consumer market. Similarly, the domestic silver investment market will also be more and more perfect, and more investment channels and products will emerge as the times require to meet the people's increasingly rich investment needs. Dry Foam Brick,Floral Foam For Artificial Flowers,Dry Foam For Artificial Flowers,Dry Floral Foam Bricks SHANGHAI WELLONG IMPORT AND EXPORT CO., LTD , https://www.shanghaifloralfoam.com