水合肼还原-EDTA滴定法测定氧化钯中钯

氧化钯使用常规的酸溶方法难溶。采用水合肼作为还原剂,于80 ℃时,在氧化钯的悬浮水溶液中,将氧化钯还原为金属钯黑,过滤后,该金属钯黑连同滤纸经过盐酸及硝硫混酸碳化处理后,钯进入溶液,从而解决了难溶氧化钯的溶样难题。然后,于pH 5.8的醋酸-醋酸钠缓冲介质中,以二甲酚橙为指示剂,锌盐返滴定过量EDTA,用丁二酮肟析出与钯等量的EDTA,三氯甲烷萃取丁二酮肟-钯沉淀,锌盐滴定析出的EDTA以测定钯含量,从而建立了水合肼还原-EDTA滴定法测定难溶氧化钯中钯的方法。按照实验方法测定实际样品中钯,结果的相对标准偏差(RSD,n=5)在0.12%～0.20%之间。对基准物质氧化钯中钯进行分析,测定值与理论值相符合。

Determination of palladium in palladium oxide by EDTA titration with hydrazine hydrate reduction

The palladium oxide was hardly dissolved by the common acid method. In proposed study, the palladium oxide was reduced to the metal palladium black in supernatant solution at 80 ℃ using hydrazine hydrate as reducing agent. After filtration, the metal palladium black with filter paper was treated by carbonization with hydrochloric acid and nitric-sulfuric acid. The palladium was introduced into solution, solving the sample preparation problem of indissolvable palladium oxide. Then, the excessive EDTA was back-titrated with zinc salt in HAc-NaAc buffer solution at pH 5.8 using xylenol orange as indicator. The equal amount of EDTA to palladium was precipitated with dimethylglyoxime. The dimethylglyoxime-palladium precipitate was extracted with trichloromethane. The precipitated EDTA was titrated with zinc salt to determine the content of palladium. Thus, the determination method of palladium in indissolvable palladium oxide by EDTA titration with hydrazine hydrate reduction was established. The content of palladium in actual sample was determined according to the experimental method. The relative standard deviations (RSD, n=5) were between 0.12% and 0.20%. The proposed method was also applied to the determination of palladium in certified reference material of palladium oxide, and the found results were consistent with the theoretical values.