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通过缓慢滴加焦磷酸钾的硝酸溶液到钼酸铵溶液中制得了大颗粒磷钼酸铵(AMP)。研究了AMP的成核速率(G)与晶体生长速率。与晶体生长速率相比成核速率的反应级数更高。最初,大颗粒磷钼酸铵的结晶过程处于相变反应控制的动力学区域,此时溶液的过饱和生成速率比过饱和消除速率高。晶体线生长速率与溶液的过饱和度先增加后降低。在滴加中期,过饱和消除速率增长到与其生成速率相当。在滴加后期,晶体成核速率快速增高,而晶体的线生长速率下降。晶体的成核速率成为过饱和消除的唯一控制步骤。因此,AMP成核大部分是在首先接触到滴加液的局部溶液中完成的。
Large particle ammonium phosphomolybdate (AMP) was prepared by slowly dropping a solution of potassium pyrophosphate in nitric acid into ammonium molybdate solution. The nucleation rate (G) and crystal growth rate of AMP were investigated. The reaction rate of the nucleation rate is higher than that of the crystal growth rate. Initially, the crystallization process of the large particle ammonium phosphomolybdate was in the kinetic region controlled by the phase change reaction, at which time the supersaturation formation rate of the solution was higher than the supersaturation elimination rate. Crystalline line growth rate and solution supersaturation first increased and then decreased. During the middle of dripping, the rate of supersaturation elimination increased to a rate comparable to its rate of formation. At the end of the dropwise addition, the rate of nucleation increases rapidly, whereas the rate of crystal growth decreases. The nucleation rate of the crystal becomes the only control step for supersaturation elimination. Therefore, most of the nucleation of AMP is done in the first place in contact with the dropping solution.