What is ammonium paratungstate? Ammonium paratungstate (APT) is a kind of white crystal with two forms of flake and needle, slightly soluble in water, insoluble in alcohol; it is mainly used for manufacturing ammonium metatungstate (AMT), tungsten trioxide (WO₃) and blue tungsten oxide ect., and also being the raw material of other tungsten compound; others, APT can also be used to produce catalyst.

Chinese Name: 仲鎢酸銨
English Name: Ammonium Paratungstate
English Abbreviation: APT
Molecular Formula: H₈N₂O₄W
Molecular weight: 283.9145
Melting Point: 3410 °C(lit.)
Boiling Point: 5660 °C (lit.)
Density: 4.61g/cm3
EINECS: 234-364-9
CAS Number: 11120-25-5
Dangerous Goods Mark: F,Xi
Hazard Category Code: 11-36/38-36/37/38
Safety Instructions: 6-26-36
Dangerous Goods Transport No.: UN 3089 4.1/PG 2
RTECS Number: YO7175000
Hazard Class: 8
APT will have forms of crystal under different crystallization conditions, such as:
1.3(NH₄)₂O-7WO₃-6H₂O ；
2.5(NH₄)₂-12WO₃-5H₂O；
3.5(NH₄)₂O-12WO₃-5H₂O；
4.5(NH₄)₂O-12WO₃-11H₂O
Appearance: White crystal with two forms of flake and needle.
Solubility: Slightly soluble in water (the solubility is less than 2% in water under 20℃) and will increase slightly with the raising of temperature, insoluble in alcohol.
Thermal Decomposition: Ammonium paratungstate will lose part of ammonia and water when heated to 220~280℃ and transferred into ammonium metatungstate (AMT); when heated to 600℃ or higher temperature, APT will lose all the ammonia and water and become yellow tungsten trioxide completely.