新显色剂二溴硝基偶氮氯膦的研究和应用 Ⅱ.光度法直接测定镍基合金中的铈组稀土

STUDY ON A NEW CHROMOGENIC REAGENT-DIBROMO-p-NITROCHLOROPHOSPHONAZO (DBNCPA) AND ITS APPLICATION Ⅱ.SPECTROPHOTOMETRIC DETERMINATION OF CERIUM-SUBGROUP RARE EARTHS IN NICKEL-BASE ALLOYS

二溴硝基偶氮氯膦是一种新的稀土显色剂。该试剂在酸性溶液中为紫红色,与铈形成蓝绿色的配合物,配合比为3:1。试剂与铈组稀土的显色反应体系简单、显色酸度高、范围宽、不但灵敏度高,而且选择性好。应用于钇组稀土存在下测定镍基合金中的铈,结果令人满意。

The DBNCPA reacts with cerium-subgroup rare earths to form coloured complexes in a medium of hydrochloric acid having a composition of 1:3, and showing an absorption peak at 642nm. The stability constant of the complex has been estimated to be 3.91×10^(16) by Job's continuous variation method. The reagent is highly sensitive and selective.The molar absorptivities for cerium-subgroup rare earths are 1.07-1.10×10~5 L·mol^(-1)·cm^(-1), and yttrium-subgroup rare earths as well as other foreign ions can be completely masked by oxalic acid.The reagent has been used to detormine cerium in nickel-base alloys with satisfactory results.