Evaporation crystallization method is the most important production method to prepare APT (ammonium paratungstate) at present, because it is no need to add extra agent, and will not introduce new impurity, besides, the crystallization process can further remove impurity to ensure the quality of products.
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Preparation of Ammonium Paratungstate by Evaporation Crystallization Method
At a constant temperature of 80 °C, use an evaporation crystallizer to heat and evaporate the ammonium tungstate solution and stir with a variable speed stirrer. When there are tiny crystal nuclei, reduce the stirring speed and continue to evaporate until the mother liquid is 1/3 of the original liquid, stop the evaporation, and filter while hot. First wash it with 2% dilute ammonia water 1-2 times, then wash it with distilled water 3-4 times, put it in a vacuum drying oven at 50 °C for 5-6 h to obtain APT crystals.
