Ammonium metatungstate and tungsten trioxide are distinctly different in several ways, and the following is a detailed comparison of the differences between them:
Definition and chemical formula of ammonium metatungstate and tungsten trioxide
Ammonium metatungstate
is an inorganic compound whose chemical formula is usually expressed as (NH₄)₆H₂W₁₂O₄₀-xH₂O, where x denotes the amount of water of crystallization. It appears as a white crystalline powder or slightly yellow in color.
Tungsten trioxide
is an inorganic substance with the chemical formula WO₃ and is a yellow powder.
Physical Properties of Ammonium Metatungstate and Tungsten Trioxide
Ammonium metatungstate
It is soluble in water but insoluble in alcohol. Its solubility is affected by temperature, such as at 20℃, the solubility of ammonium metatungstate in water is 303.9g/100gH₂O.
Tungsten trioxide
Insoluble in water, soluble in alkali, slightly soluble in acid. Its melting point is 1473℃ and boiling point is 1750℃.
Chemical properties of ammonium metatungstate and tungsten trioxide
Ammonium metatungstate
will lose ammonia and water of crystallization under heating conditions, and transform into other tungsten compounds. For example, when heated above 600°C, it will completely decompose into tungsten trioxide.
Tungsten trioxide
is stable in air and slowly dissolves in ammonia and concentrated hot sodium hydroxide solution.
Uses of Ammonium Metatungstate and Tungsten Trioxide
Ammonium metatungstate
It is mainly used in the manufacture of metallic tungsten, alloy steel, fireproof fabrics, etc., and is widely used in the ceramic industry. In addition, it is also the main raw material of tungsten-based catalysts in oil refineries, and is used in the manufacture of various petrochemical catalysts and other tungsten compounds.
Tungsten Trioxide
It is mainly used for making high melting point alloys and cemented carbides, manufacturing tungsten wires and fireproofing materials. In the ship industry, it is used as important anticorrosive paint and coating materials.
Preparation Method of Ammonium Metatungstate and Tungsten Trioxide
Ammonium metatungstate
Ammonium metatungstate can be prepared by various methods, such as taking ammonium tungstate or sodium tungstate as raw material, obtaining ammonium metatungstate solution by solvent extraction or ion exchange method, and then obtaining the product by evaporation and crystallization. It can also be converted to ammonium metatungstate by heating ammonium paratungstate.
Tungsten Trioxide
Usually obtained by co-melting tungsten ore with soda ash and then adding acid.
Safety of Ammonium Metatungstate and Tungsten Trioxide
Ammonium metatungstate
Although it has no harmful components, it is slightly acidic and needs to be handled properly to avoid skin or eye contact.
Tungsten Trioxide
Although low in toxicity, it is irritating to the eyes and skin. When melting tungsten steel, workers may experience symptoms such as generalized weakness and fever, which may be related to inhalation of tungsten trioxide.
To summarize, there are significant differences between ammonium metatungstate and tungsten trioxide in terms of definition, physical properties, chemical properties, uses, preparation methods and safety. These differences determine that they play different roles in different industrial fields and applications.
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