Silver is a transition metal. Chemical symbol Ag. Silver is one of the metals known and used in ancient times, and it is an important precious metal. Silver exists in the form of simple substance in nature, but most of it exists in silver mines in the form of bound state. Silver has relatively stable physical and chemical properties, good thermal and electrical conductivity, soft texture and rich ductility. Its reflectivity is extremely high, reaching over 99%. It has many important uses.
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The specific gravity of silver is also called the density of silver. Compared with water at 4℃, the density of silver is 10.49 g/cm3.
In ancient times, people knew about silver. Like gold, silver is a precious metal with a long history of application, which has a history of more than 4,000 years. Archaeologists in China discovered a "gold-silver fault" (a pattern inlaid with gold and silver wires) embedded in the surface of bronze wares unearthed in the Spring and Autumn Period.
The silverware unearthed in the ancient tombs of the Han Dynasty is very beautiful. Because of its unique excellent characteristics, silver is endowed with dual values of currency and decoration. In ancient times, the biggest use of silver was as a medium of commodity exchange-money. The pound and silver dollar used before the liberation of China were both silver-copper alloys.
Silver is not easy to react with sulfuric acid, so sulfuric acid can be used to clean the copper oxide fire marks left by silver welding annealing in jewelry manufacturing. Silver easily reacts with sulfur and hydrogen sulfide to form black silver sulfide, which is often found on tarnished silver coins or other articles. Silver can react with oxygen at high temperature to produce brown-black silver oxide (it can also react at room temperature, but the speed is very slow).
In the presence of potassium bromide (KBr), metallic silver will be eroded by strong oxidants such as potassium permanganate or potassium dichromate. These compounds are used in photography to bleach visible images and convert them into silver halide, which can be removed by sodium thiosulfate and re-developed to enhance the original images.
Adding chloride ion into silver nitrate solution will precipitate silver chloride (AgCl), which is insoluble in water and dilute nitric acid, so silver nitrate solution is often used to test the existence of chloride ion. Similarly, adding bromine salt or iodized salt can precipitate other silver halides used to make photographic emulsions.
Silver chloride is used to make glass electrodes for detecting pH value and measuring potential, and transparent cement is used for glass. Silver iodide (AgI) can be scattered in the clouds for artificial rainfall. Silver halide is highly insoluble in aqueous solution (except silver fluoride), so it is often used in gravimetric analysis.
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