pH value affects average particle size and particle of ammonium paratungstate crystal; also the nucleation rate and the crystal growth rate are obviously influenced by pH value. The hydrogen ion concentration index is the ratio of the total amount and the total amount of the hydrogen ion in the solution, which is commonly called "pH", value of the acidity or alkalinity of the solution, that is, the negative value of common logarithm of the hydrogen ion concentration.When the pH of solution equals to 9, adding HCL solution concentration of 1% will cause the pH decreased, and crystallization rate of APT decreased afterwards. Set experiment conditions bellows: 60℃ water bath reaction, exposure to stir. It resulted that solution produced milk white precipitate when the PH>8 and disappeared immediately after stirring; but precipitation difficult to disappear even stirring when PH<8.

 

NHC4+ hydrolysis H+ making PH suddenly decline when PH<8.2. Setting pH value range 8~7.8 after spontaneous nucleation which is superior to the 7.6~7.4, advantage to reduce the number of nuclei and the rate of formation, making the small amount of crystal nuclear steadily growing large granular products. Moreover, a narrow range of PH is beneficial to the uniform distribution of the coarse grains of ammonium. When 10% to 20% of the dilute hydrochloric acid injected to adjust pH to 6.5~7.5, then crystalline particles bulk density decreases, crystal shape regular, especially suitable for production of fine particles of ammonium paratungstate. By adjusting the crystal liquor ideal PH to 6.0~8.0, and heated up to 50℃, we obtain high purity ammonium paratungstate crystal.