Ammonium paratungstate and ammonium metatungstate are not the same products; ammonium paratungstate and ammonium metatungstate are significantly different in several aspects, and the following is a detailed explanation of the differences between them:
Definition and molecular formula are different
Ammonium paratungstate
is a chemical substance with the molecular formula (NH₄)₂W₂O₇, also often expressed as (NH₄)₂O-12WO₃ or (NH₄)₂[H₂W₁₂O₄₀] -xH₂O (where x represents the amount of water of crystallization). It refers to the sulfate of tungsten, which has low solubility and does not readily decompose with heat.
Ammonium metatungstate
is an inorganic compound, but with a different molecular formula than ammonium secotungstate, usually HN₆OW (note that the molecular formula here may vary depending on the literature and the specific application). Ammonium metatungstate is a type of tungstate that decomposes easily with heat.
Different physical and chemical properties
Ammonium paratungstate
Monoclinic crystal system of fine transparent crystals or white crystals, relative density 2.3, soluble in water but insoluble in ethanol. Aqueous solution is weakly acidic. When heated in air, it starts to remove part of ammonia molecules when it is lower than 100℃, and all ammonia molecules and water of crystallization are removed when it is strongly heated, and it turns into tungsten trioxide yellow powder.
Ammonium metatungstate
It is usually white crystalline powder or slightly yellow, and its water solubility is better than ammonium paratungstate.
Different uses
Ammonium paratungstate
It is mainly used to manufacture tungsten trioxide or blue tungsten oxide to make metallic tungsten powder. In addition, it is also used in the manufacture of ammonium metatungstate and other tungsten compounds, and as an additive in petrochemical industry.
Ammonium metatungstate
Ammonium metatungstate is widely used as an additive in welding, cutting and other processes, as well as in the manufacture of tungsten metal, alloy steel, fire-resistant fabrics, etc., and in the ceramic industry. In addition, it is also the main raw material for tungsten-based catalysts in oil refineries.
Different production processes
Ammonium paratungstate
There are various production processes, including wolframite concentrate high-pressure alkali cooking-ion exchange-evaporation and crystallization method, scheelite concentrate soda pressure cooking-ion exchange-evaporation and crystallization method, etc.
Ammonium metatungstate
There are also many methods for its production, such as taking ammonium tungstate solution as raw material, using solvent extraction or ion exchange method to produce ammonium metatungstate solution first, and then getting ammonium metatungstate by evaporation and crystallization; or taking ammonium paratungstate as raw material, converting it into ammonium metatungstate by heating and thermal dissociation, and so on.
To summarize, there are obvious differences between ammonium paratungstate and ammonium metatungstate in terms of definition, molecular formula, physicochemical properties, usage and production process. Although both compounds contain tungsten, they have different uses and preparation methods in industrial applications due to their different structures and properties.
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