杂多酸制备中pH调节问题？把pH值调到5以后，然后搅拌一会儿后ph值又降下来了，要把pH值又调回5。缓缓滴加，是要防止加的过快使ph超过5了。最好是边搅拌边滴加上一会儿后，看PH变化，调到5后，每隔一段时间检查一下ph，若下降太多，仍要调到5. 谢谢你，那我调到5以后，搅拌了大概有一小时，我测ph值得时候，大概又降到4了，我调到5，这样对吗？还有一个特别棘手的事，我合成出的单缺位的硅钨酸盐极易溶于水，怎么重结晶了，能给我具体指导一下吗？文献表述如下：First PW12 (2.88 g) was dissolved in water (10 mL) and the pH of the solution was adjusted to 4.8 using NaHCO3 solution. This resulted in the formation of lacunary heteropoly anion [PW11O39]7. The solution having pH 4.8 was heated to 90 C with constant stirring. Then to it a solution of Co(NO3)26H2O (0.29 g) in water (10 mL) was added. The NaCoPW11 was obtained by solvent evaporation, and recrystallization from water, followed by subsequent drying at 110 C for 12 h，查看更多
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