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磷铁中磷的测定,以往都是先用酸分解细粉试样,然后稀释,分取部分试液,用高锰酸钾氧化,在试液呈酸性情况下加入钼酸铵溶液,把溶液中存在的磷酸沉淀为络盐形式的磷钼酸铵,最后用酸碱中和滴定法定量。就整个分析过程说,手续上并不十分简便。分析所需时间约在一小时左右,也跟不上快速法对时间的要求。这对炉前来说是不够理想的。现在我们参考了文献,采用在氨性试液内加入过量镁标准溶液,使与试液中的磷酸在强氨性情况下,结合生成磷酸铵镁的沉淀。在沉淀和过量镁的标准溶液共同存在的情况下,利用EDTA 与镁生成稳定而可溶性络合物的性能,络合滴定所加过量的镁,以间接换算来测定磷铁中磷的含量。这个方法我们在实际应用上,无论对分析结果、操作手续及所需时间都是令人满意的。下面是我们多次平行测定的结果:
Determination of phosphorus in iron and phosphorus in the past are the first use of acid decomposition of fine powder samples, and then diluted, part of the test solution, with potassium permanganate oxidation, in the test solution was acidic ammonium molybdate solution, the solution The phosphoric acid precipitate present is the ammonium phosphomolybdate in the complexed salt form and is finally quantified by acid-base neutralization titration. As to the whole analysis process, formalities are not very simple. Analysis of the time required for about an hour, also can not keep up with the fast method of time requirements. This is not ideal for the furnace front. Now we refer to the literature, the use of ammonia in the test solution by adding excess magnesium standard solution, and the test solution of phosphoric acid in the case of strong ammonia, the formation of ammonium phosphate precipitation. In the presence of precipitated and excess magnesium standard solutions, EDTA and magnesium are used to generate stable and soluble complexes, the excess magnesium is complex titrated, and the phosphorus content of the iron and phosphorus is measured indirectly. This method we in the practical application, regardless of the analysis results, procedures and time required are satisfactory. Here are the results of our multiple parallel assays: