Ammonium Metatungstate AMT

AMT corresponds to the formula (NH4)6H2Wi204o XH2O. The amount of combined water is variable. Usual technical products contain 3 to 4 molecules. Further dehydration may lead to insoluble compounds. 

The importance of AMT lies in its extremely high water solubility. This is why AMT has gained increasing usage as an intermediate in a variety of applications like chemicals and catalysts. 

The latter three methods are preferred today for industrial production, since acidification and thermal decomposition result in lower-quality products (less purity and amorphous structures respectively). 

The resulting solution is evaporated to a syrup from which white crystals are recovered. The yield is better than 99%. 

Properties. AMT is a white crystallized powder having a density of 4g/cm. Decomposition starts at 100 °C and, between 200 and 300 °C, it converts to the anhydrous form. Further decomposition leads to WO3. 

---