论文部分内容阅读
在某些特效试剂尚不适用于球墨铸铁中残余含镁量的测定之前,EDTA络合滴定仍然是一个可靠的方法。可是由于EDTA与镁络合的pH条件下的高度灵敏性和相对降低的选择性,各种干扰离子的分离或隐蔽的彻底与否,就成为决定成败的关键。大量的铁的分离,残余的铁、铝以及其他元素的隐蔽或去除是没有困难的。问题是在残余的锰。锰的干扰不是表现在易于破坏铬黑T指示剂,而是在于小量锰的不易去除或有效地加以隐蔽,从而严重地影响了稳定性和重现性,使滴定的结果不得不依靠对含量相接近的已知含镁量的标准试样的滴定度来计算,而不能用滴定剂的当量浓度来计算,因而产生很大的误差。
The EDTA complexometric titration is still a reliable method until certain special effects reagents are not yet suitable for the determination of the residual magnesium content in ductile iron. However, due to the high sensitivity and relatively low selectivity of EDTA in complexing with magnesium, the separation or concealment of various interfering ions is the key to success or failure. Large amount of iron separation, residual iron, aluminum and other elements of the concealment or removal is not difficult. The problem is the residual manganese. Manganese interference is not manifested in easy to destroy chrome black T indicator, but rather a small amount of manganese is not easy to remove or effectively be concealed, thus seriously affecting the stability and reproducibility, the titration results have to rely on the content Close to the known standard magnesium content of the sample to calculate the titer, and can not be calculated using the equivalent concentration of titrant, resulting in a large error.