What Is Ammonium Paratungstate

What is ammonium paratungstate? Ammonium paratungstate is white crystalline of flake or needle shape, it is short for APT.

Chemical formula: H8N2O4W
Molecular Weight: 283.9145
EINECS: 234-364-9
CAS No.: 14311-52-5

According to different crystalline condition, its chemical formula has different forms:
(1)3(NH4)2O•7WO3•6H2O
(2)5(NH4),2•12WO3•5H2O
(3)5(NH4)2O•12WO3•5H2O
(4)5(NH4)2O•12WO3•11H2O
Ammonium paratungstate is usually in forms of pentahydrate and decahydrate:
1.Decahydrate: chemical formula is 5(NH4)2O•12WO3•10H2O, molecular weight is 3222.73. It is produced by evaporate tungstic acid soluble in ammonium solution, has the shape of needle and flake, insoluble in water, soluble in boiled water, lose crystal water in dry air, add in overdosed hydrochloric acid or nitric acid will separate out tungstic acid.
2. Pentahydrate: Chemical formula is 5(NH4)2O•12WO3•5H2O.

Ammonium paratungstate is slightly soluble in water, solubility is less than 2% under 20℃, insoluble in ethanol. Ammonium paratungstate has thermal decomposition property, when heat to 220~280℃, it will lose part of ammonium and crystal water and convert into ammonium metatungstate. When heat to over 600℃, it will lose all of ammonium and crystal water and convert into tungsten trioxide.

Application of ammonium paratungstate (APT)
Ammonium paratungstate as intermediate material of powder metallurgy industry, its application is listed as below:
1. It is used to produce yellow tungsten oxide or blue tungsten oxide, then used to produce tungsten metal powder and other tungsten products such as tungsten wire, tungsten rod and tungsten carbide products. It is also the main application of APT.
2. Under thermal decomposition it can be used to produce ammonium metatungstate.
3. For most of tungsten products, APT is the mostly used high purity intermediate product. According to the heredity of tungsten property, another application of APT is used as laboratory reagent to produce tungstic acid, tungsten metal powder or tungsten carbide. 4.Coloring agent in ceramic industry.
5. Catalyst.
6. Water absorbent gel.
7. Produce ammonium phosphotungstate and other tungsten compounds.

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