Effect of Time on Ammonium Paratungstate Production

Here is the discussion of effect of time on ammonium paratungstate production.

Evaporation and crystallization including the heating time (heating rate) and the evaporation time (evaporation rate). When the heating time is quick, most of the free ammonia in solution were expelled in a short time, so that PH of the solution decreased rapidly, and the over-saturation increases, and a lot of nuclei was formed rapidly, the particle size became finer. Long evaporation time, it will help small crystals dissolve constantly, big crystals continue to grow. the situation of crystal growth becomes more apparent when APT crystalline precipitate for a while before filtered. It was also found in the conditions of a certain degree of vacuum, evaporation speed increases, the bulk density of the resulting APT reduces significantly.