Preparation of concentrated aqueous solutions of - ammonium metatungstate from aqueous suspensions of

摘要

Ammonium metatungstate solutions are prepared from relatively insoluble ammonium paratungstate by (a) forming an aqs. suspension containing up to 22% wt ammonium paratungstate, calculated on the content of WO3, (b) maintaining the pH of the aqs. suspension at 1-75-3.5 by the addition of hydrogen ions, and (c) maintaining the temperature of the suspension at 50-120 degrees C until the ammonium paratungstate has been dissolved and converted into metatungstate. - The process enables ammonium metatungstate solutions to be more cheaply prepared, as ammonium paratungstate is cheaper than ammonium metatungstate. The process is convenient and efficient, and can be carried out using the commercially available refracting form of ammonium paratungstate. - Concentrated solutions of the metatungstate can be easily prepared.