稀土元素—铬—钼体系的组成分析

A METHOD OF COMPOSITION ANALYSIS FOR THE SYSTEM OF RARE EARTH MOLYBDENUM-CHROMIUM

本文详细研究了稀土元素、钼、铬体系中各元素定量测定的诸方面条件 ,提出了一种简单易行 ,测量准确 ,于一般条件下即可操作的常量分析的新方法 ,对于稀土矿物的成分测定具有指导作用 .

In this paper, we have proposed a new method of quantitative analysis for the system of rare earth molybdenum-chromium. When the pH of solution is 2, rare earth is successfully determined through precipitation analysis by adding oxalic acid at 50~60℃. Molybdenum can be detemined by α-benzoin oxime,which forms precipitation with molybdenum quantitatively in acid solution. Chromium is determined by back-titration. First the excess of ethylenediaminetetraacetate is added into acid solution of chromium to form the red-violet chromium EDTA complex, then the free EDTA is titrated with the manganous salt in NH 3-NH 4Cl buffer. The Erichrome black T is used as an indictor and rare earth element is masked by NH 4F during the titration. So this method of composition analysis for the system is new and has a high sensitivity and accuracy, Furthermore, it is simple and easy to practice and convenient to employ in the laboratory, which has the common condition. It will be helpful for determination the composition of mineral as well as new type heterpoly acid.