研究了酸碱中和法制备亚磷酸镁的反应条件,探究了亚磷酸与碳酸镁以不同配比进行反应时对所得产物的影响,采用X射线衍射（XRD）、电位滴定、氧化还原滴定等方法对制备的产物进行了表征。结果表明,当亚磷酸与碳酸镁物质的量比约为1.0时形成的是6水合亚磷酸镁;当亚磷酸与碳酸镁物质的量比约为2.0时则形成了酸式盐即0.33水合亚磷酸氢镁;当亚磷酸与碳酸镁物质的量比偏离1.0和2.0较远时,有形成非晶态物质的倾向。氧化还原滴定法测定亚磷酸与碳酸镁物质的量比为1.0所得产物时,以亚磷酸计质量分数为72.66%,折算成亚磷酸镁质量分数为92.43%;测定亚磷酸与碳酸镁物质的量比为2.0所得产物时,以亚磷酸计质量分数为84.79%,折算成亚磷酸氢镁质量分数为96.32%。电位滴定分析结果表明,亚磷酸镁盐滴定曲线有两个突跃,与亚磷酸的二元酸的性质吻合。

The reaction conditions of magnesium phosphite prepared by acid-base neutralization were studied.The effects of reaction of magnesium carbonate with phosphorous acid at different ratios on the reaction products were investigated.The products were characterized by XRD,potentiometric titration,redox titration and other methods.The results showed that magnesium phosphite hexahydrate was formed when the amount-of-substance ratio of phosphorous acid to magnesium carbo-nate about 1.0.An acid salt was formed when the amount-of-substance ratio of phosphite to magnesium carbonate about 2.0,that is,it can be formed 0.33 magnesium phosphite hydrate.There was a tendency to form amorphous substances when the amount-of-substance ratio of phosphite to magnesium carbonate was far away from 1.0 and 2.0.The mass fraction of magnesi-um phosphite was 72.66% when the amount-of-substance ratio of phosphite to magnesium carbonate was 1.0 by redox titra-tion,and converted into the mass fraction of six water phosphite magnesium was 92.43%.The mass fraction of phosphorous acid of the product was 84.79% when the amount-of-substance ratio of phosphorous acid to magnesium carbonate was 2.0,and converted into the mass fraction of hydrogen phosphite magnesium was 96.32%.The results of potentiometric titration showed that the curve of magnesium phosphite salt had two jumps,which were consistent with the properties of diacid phosphite.