沉淀分离-铅试金富集-氯化钠电位滴定法测定贵铋中银

对贵铋中银采用铅试金法富集后再测定时,存在铋干扰银的富集从而使得银的测定结果偏低的问题。实验采取硝酸、氟化铵和高氯酸分解样品后,加入EDTA溶液以络合铋,加入氯化钠使银以氯化银沉淀的形式析出,而铋仍留在溶液中,过滤,实现了铋与银的分离,从而消除了铋对银富集的干扰。分离铋后,用铅试金法使沉淀中银富集于合粒中,用硝酸溶解合粒,最后用氯化钠电位滴定法测定,据此建立了沉淀分离-铅试金富集-氯化钠电位滴定法测定贵铋中银的分析方法。探讨了贵铋样品中共存组分(铋、钙、铅、铁、锌、锡、锑、砷、铜和金)对银测定结果的影响,结果表明,样品中共存组分对银的测定无影响。按照实验方法对4个贵铋实际样品中银进行测定,测定结果的相对标准偏差(RSD, n=10)为0.26%~0.68%,加标回收率在99%~101%之间,所得结果与重量法的测定值相吻合。

Determination of silver in noble bismuth by precipitation separation-lead fire assaying enrichment-sodium chloride potentiometric titration method

When the content of silver in noble bismuth sample was determined after enrichment by lead fire assaying, bismuth would interfere the enrichment of silver which lead to lower determination results of silver. The sample was dissolved with nitric acid, ammonium fluoride and perchloric acid. EDTA solution was added for the complexing of bismuth. Sodium chloride was added to react with silver to form silver chloride precipitation while the bismuth was remained in solution. The separation of bismuth and silver was achieved by filtration, thus eliminating the interference of bismuth with the enrichment of silver. Then, the silver in precipitation was enrichment into composite granule by lead fire assaying. The composite granule was dissolved with nitric acid for the determination of silver by sodium chloride potentiometric titration. Consequently, an analysis method of silver in noble bismuth was established by precipitation separation-lead fire assaying enrichment-sodium chloride potentiometric titration. The influence of coexisting components (bismuth, calcium, lead, iron, zinc, tin, antimony, arsenic, copper and gold) in noble bismuth on the determination of silver was discussed. The results showed that the coexisting components in samples did not interfere with determination of silver. The experimental method was applied for determination of silver in four actual samples of noble bismuth. The relative standard deviations (RSD, n=10) of determination results were between 0.26% and 0.68%. The spiked recoveries ranged from 99% to 101%. The determination results were consistent with those obtained by gravimetry.