铂、钯、钴合金中钴的选择性测定

Selective Determination of Cobalt in Platinum,Palladium and Cobalt Alloys

建立了EDTA络合锌盐滴定选择性测定Co的方法,考察了不同类型的酸及酸浓度对EDTA络合Co(Ⅲ)及滴定终点的影响,研究了提高方法选择性的条件。结果表明:于0.1~1.0 mol/LHNO3、0.1~1.0 mol/L HC l、0.024~0.24 mol/L H2SO4和0.001~0.078 mol/L HC lO4酸浓度内,EDTA-Co络合物稳定,且滴定终点敏锐;测定5.00~20.00 mg Co(Ⅲ),相对误差-0.20%^+0.24%,样品加标回收率99.40%~100.40%;采用联合掩蔽剂能消除30余种共存元素的影响;方法准确度高,选择性好,操作简便,适用性强,已用于Pt、Pd、Co合金中质量分数为5%~75%Co的测定,结果满意。

A method for selective determination of cobalt using EDTA complex and zinc salt titration was proposed. The effects of the kinds of acid and their acidity on EDTA complex of cobalt （ Ⅲ） and titration end -point were studied. The conditions for improving selectivity of the method were also discussed em- phatically. The results indicated that the EDTA - Co complex is stable and the titration end - point is sensitive in the acidity range of 0.1 - 1.0 mol/L HNO3, 0. 1 - 1.0 mol/L HC1, 0. 024 -0.24 mol/L H2SO4 and 0.001 - 0.078 mol/L HClO4. The relative error is - 0.20% - ＋ 0.24% for the determination of 5. 00 - 20.00 mg cobalt（Ⅲ） and the recovery of Co in samples with the addition of standard cobalt is 99. 40% -100.40%. More than 30 elements are noninterference using combined masking reagent. The pro- posed method has high accuracy, good selectivity, convenient operation, better applicability and was applied to determine cobalt in platinum, palladium and cobalt alloys containing 5wt% - 75wt% cobalt with satisfactory results.