邻菲啰啉氯仿萃取铈盐滴定法测定铁的价态

DETERMINATION OF THE VALENCE STATE OF IRON BY PHENANTHROLINE-CHLOROFORM EXTRACTION AND CERIUM(Ⅳ)TITRATION

作者提出的TBP萃取容量法,成功地测定了Fe(Ⅱ)和Fe(Ⅲ)的EDTA体系(不含S_2O_3^(2-))中铁与EDTA的含量。但由于酸性介质中S_2O_3^(2-)还原Fe(Ⅲ),故该方法不能用来测铁的价态。而K_2Cr_2O_7滴定Fe^(2+)及Ti^(3+)滴定Fe^(3+)测定铁价态的方法,由于S_2O_3^(2-)的干扰也不能应用。因此研究该体系铁的价态分析是十分必要的。

Description is given of a method for determination of the ratio of different valence state of iron in a S_2O_3^(2-) -containing system of Fe(Ⅱ)(Ⅲ)-EDTA. At pH of 6—10, Fe(phen)_3(ClO_4)_2 can be extracted by CHCl_3 in the presence of EDTA quantitatively. Addition of a little alcohol improves the extraction. When concentration of HCl is 6-10M, Fe(phen)_3^(2+) can be back extracted into aqua phase. Fe(Ⅲ) in FeY^- can be reduced by NaH_2PO_2 in acidic medium. Separated Fe(phen)_2^(2+)may be titrated with standard Ce^(4+) solution. At pH of 6—9,S_2O_3^(2-) does not affect the separation and determination of Fe(Ⅱ).