Precipitation of fine single crystal of sparingly soluble salt

在308 K下，在间歇式搅拌容器中进行硝酸铅溶液与硫酸反应得到的溶液中的硫酸铅的结晶试验，研究铅离子浓度的下降速率与生长的硫酸铅晶体的尺寸分布之间的相关性。在过饱和溶液中得到了尺寸相对均匀的晶体，其浓度以与过饱和度成正比的速率下降。在这些试验中，将单独制备的溶液一次性混合，粒度分布均匀性受进料初始阶段混合条件的影响。在一些试验中，粒度分布变宽。其他试验也在两升体积的CDJ（受控双射流）结晶器中进行，该结晶器被设计成使两种溶液充分混合。在这些试验中，将硝酸铅或硫酸钠的水溶液通过单独的管道分别加入到结晶器中的混合明胶溶液中，并进行反应。为了获得均匀的所需尺寸的晶体，这些试验在操作中分批进行，所述操作的条件被选择为使得成核在初始阶段发生并在短时间内完成。在接下来的步骤中，期望生成的核生长到所需尺寸的晶体而不成核。主要操作条件为：硝酸铅或硫酸钠料液浓度分别为0.10mol/l。溶液的进料速率为10 ml/min，在结晶器中的混合溶液中的乙酸和明胶的浓度为1.74 × 10 ~（-6）<-1>mol/l，初始阶段为2wt%。在过量pPb或PS 04的操作液浓度为2或3时，在过量pPb的操作液浓度为2时，可得到平均粒径为4.5 μ m，效价系数约为15%的菱形晶体。

Precipitaion tests of lead sulfate in a solution obtained by reaction between lead nitrate solution and sulfuric acid, were carried out in a batch agitated vessel at 308K, and a correlation between a decreasing rate of a concentration of lead ion and a size distribution of lead sulfate crystals grown, was studied. A relatively uniform size crystal was obtained in the supersaturated solution whose concentration decreased on the rate proportional to a supersaturation. On these tests, the solutions prepared separately, were mixed at one time and a uniformity of size distribution was affected by a mixing condition on initial stage of feed. On some tests, a size distribution became broad.Other tests were also done in the CDJ (Controlled Double-Jet) crystallizer of two liters on volume which was devised to make two solutions mixed well. On these tests, an aqueous solution of lead nitrate or sodium sulfate was separately fed into an mixed gelatin solution in the crystallizer through an individual pipe, and reacted. In order to obtain homogeneous desired size crystals, these tests was batchwisely carried out in the operation whose conditions were selected to make nucleation occurred on an initial stage and finished in a short period. On the following step, born nuclei were expected to grow to a desired size crystals without nucleation. The main operational conditions were as following : Concentration of feed solution of lead nitrate or sodium sulfate was 0.10mol/l, respectively. Feed rates of solutions were 10ml/min, the concentration of acetic acid and gelatin in a mixed solution in the crystallizer were 1.74x10^<-1>mol/l, and 2wt%, on initial stage. An excess concentration of operating solution was 2 or 3, on pPb or PS04, and lozenge- shape crystals whose average size and coefficient of valience were 4.5um and about 15 percent, were obtained on the operational condition of 2 on the excess of pPb.