［Molecular Formula］H2WO4
[Properties] Tungstic acid is divided into two types: white tungstic acid (WO3·nH2O) and yellow tungstic acid (WO3·H2O). White tungstic acid is a precipitate with indefinite composition, which can be converted into yellow tungstic acid after long-term boiling. Yellow tungstic acid is a compound with a certain composition. Generally speaking, tungstic acid often refers to yellow tungstic acid, which is a yellow powder or crystal with a relative density of 5.5 and a boiling point of 1473°C. Heated to 100°C, it begins to dehydrate and becomes tungsten anhydride, and is burned at high temperature to transform into tungsten trioxide. Tungstic acid is insoluble in cold water, slightly soluble in hot water, and insoluble in other inorganic acids except hydrofluoric acid. It is slightly soluble in concentrated hydrochloric acid, but can be dissolved in alkali and ammonia to form the corresponding orthotungstate.
[Use]Used in the manufacture of tungstates, metal tungsten wires and tungsten bars for electric light sources, and cemented carbide. Used as catalyst in petrochemical industry. It is also used as printing and dyeing auxiliaries, mechanical lubricants, ceramic colorants, and flame retardants for fire-resistant fabrics. Also used in the manufacture of X-ray fluorescent screens, etc.
[Brief preparation method]
①In industry, sodium tungstate is generally produced by reacting wolframite and sodium hydroxide, which is filtered and purified, and then undergoes metathesis reaction with calcium chloride solution. , to generate calcium tungstate, which is then treated with hydrochloric acid to produce tungstic acid.
② Calcium tungstate can be obtained by roasting sodium carbonate and tungsten ore or calcium tungstate ore, then leaching and purifying it in water, adding calcium chloride to precipitate it, and then It is obtained after acidolysis with hydrochloric acid.
[Safety and Protection] Packed in iron drums or wooden drums lined with double-layer plastic bags, each iron drum has a net weight of 50kg , each barrel is packed in wooden barrels with a net weight of 25kg. Do not contact with alkalis or store and transport together. Store in a cool, ventilated and dry place. In case of fire, yellow sand, water and various fire extinguishers can be used to put out the fire.
Dust can irritate the respiratory tract and skin.
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