Ammonium paratungstate (APT) is the white crystal, slightly soluble in water, insoluble in alcohol, the most important intermediate of tungsten metallurgy and for producing pure tungsten compound. At present, the main preparation method of APT is evaporation crystallization, while, with the continuous improvement of manufacture process, some creative methods have come into being.
The steps of tungstic acid method preparing ammonium paratungstate are as following:
1. Dissolve tungstic acid with ammonia water, and then add it into boiled deionized water to remove ammonia by heating with stirring, until the pH value turns to 8;
2. Add the acetic acid when the solution is boiling, and then adjust the pH value to 2~4 with dilute nitric acid;
3. Continue heat and concentrate the solution until the relative density, stop heating, and to cool down, filter;
4. The filtrate is added ethanol with complete stirring, then filtered after settlement, finally get the APT product after drying at 80℃ and crushing.