Determination of palladium in palladium-containing alloys by thiourea release-EDTA photometric titration
The accurate determination of palladium content in palladium-containing alloy is of great signifi-cance for the quality control and market trade of products.The determination of palladium in palladium-containing alloy usually adopts dimethylglyoxime EDTA complexometric titration or dimethylglyoxime gravimetry.However,these methods have some problems of visual error easily caused by endpoint judge-ment with eyes or long procedures in operation.In this study,after dissolving the palladium-containing al-loy,excessive EDTA solution was added into sample solution to complex palladium and coexisting ions.The excess EDTA was titrated with zinc standard titration until the solution color changed from yellow to red yellow,i.e.,the first endpoint.At this time,the titration volume did not participate in the calculation of results.Thiourea solution was added to complex palladium in palladium-EDTA.Same amount of EDTA to palladium was released,which was then titrated with zinc standard titration solution until the solution color changed from orange yellow to red yellow,i.e.,the second endpoint.The absorbance change was converted to the electrical signal change using photometric titrimeter to judge the titration endpoint.Consequently,a new method for the determination of palladium in palladium-containing alloy by photometric titration was established.AgPd30,AgPdCu20-28,AuPd20,AuPdNi8-22,PdW18 and PdNi40 were dissolved,and the palladium contents were determined according to the experimental method.Moreover,the palladium standard solution was added for recovery test.The results showed that the palladium content(mass fraction,the same below)in sample was in range of 7.83％-81.61％.The relative standard deviations(RSDs,n=7)of determination results were between 0.09％and 0.36％,the recoveries were between 99.6％and 100.3％.The contents of palladium in PdW18,PdNi40,AgPd30,AgPdCu20-28,AuPd20 and AuPdNi8-22 were determined for 7 times in parallel by the experimental method and industrial standard method(YS/T 372.3-2006).The found results of two methods were basically consistent.
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维普
