Yellow tungstic acid is the most common seen tungstic acid that appears as a kind of light yellow powder or crystalline with a melting point of 1473°C. It can not easily dissolve in phosphorus acid when it is fresh produced.
It is insoluble in water. And it will be colloidizing after dipping so that it is soluble in ammonia solution, alkali solution and high concentrate hydrochloric acid.
Its content will be different along with the changes of producing conditions. When content is WO3•H2O, its density is 5.5g/cm3, dehydrate in 100°C.
Producing Method
It can be produced by the reaction between Na2WO4•2H2O solution and HCl. It turns into sodium polytungstate. Then, add in overdosed high concentration hydrochloric acid. The yellow tungstic acid produced by this method has sodium impurity. It is gradually replaced by ion exchange method and solvent extraction method in recent years.
More details, please visit:
http://www.tungsten-powder.com/white-yellow-tungstic-acid-difference.html
