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以硫酸浸取海绵铜后的残渣中含有0.x～x%的银,并有不等量的铁、铜、钴、镍、金……等存在,我们试验了在硫酸—柠檬酸介质(0.6～2.1N),以碘化钾容量法测定,Fe~(3+)500毫克,C_μ~(2+)300毫克,C_o~(2+)150毫克,N_i~(2+)100毫克,P_b~(2+)300毫克,M_o~(6+)50毫克,C_d~(2+)30毫克,B_i~(3+)30毫克,T_i~210毫克,sb~(5+)30毫克,A_s~(5+)20毫克,A_s~(3+)30毫克,S_b~(3+)30毫克,V~(2+)20毫克,A_u~(3+)3毫克不干扰测定,而H_g~+与H_g~(2+)均严重干扰,方法建议将样品预先置500℃高温灼烧驱尽,对比了滴定介质硫酸、硝酸、过氯酸、硫酸—柠檬酸,以硫酸—柠檬酸适应范围最广,0.6～2.1N终点明显,以亚硝酸钠与淀粉为指示剂,0.05N亚硝酸钠6—8滴为宜,过多终点不稳易褪色,过少终点拖长不明显。加入标准银回收率为98.8～100.7%,曾与硫氰酸盐法、原子吸收法作了对比,方法稳定、快速。分析方法:0.5克样,加入浓硝酸15毫升,低温溶解数分钟,加入1:3硫酸10毫升,继续加热溶解并蒸至冒浓厚白烟4～5分钟。冷却,以水吹洗表面皿、杯壁,此时溶液体积所控制在15～20毫升,加入10%柠檬酸5毫升,煮沸、冷至室温,加入亚硝酸钠(0.05N)6滴,1%淀粉1毫升,以碘化钾标液(0.005N)滴定至兰色为终点。随带空白。以硫酸浸取海绵铜后的的浸渣中,含有0.x—x%的银。采用原子吸收法测定,误差较大。以硫氰酸盐法测定,汞、铜、铋及有色金属离子均干扰。用氯化银沉淀使银与铜等干扰元素分离,再以硫酸冒烟除去氯离子,操作冗长费时,同时当银量大于10毫克时,部分氯化银凝聚,不能被硫酸完全分解,因而造成结果偏低。本文提出在柠檬酸——硫酸介质中,以碘量法快速测定银,方法稳定,操作简便。
After leaching sponge copper with sulfuric acid, there are 0.x ~ x% silver in the residue, and there are unequal amounts of iron, copper, cobalt, nickel, gold ... ... and so on, we tested the sulfuric acid - citric acid medium 0.6 ~ 2.1N) were determined by the method of potassium iodide volumetric method. Fe ~ (3 +) 500 mg, C_μ ~ 300 mg, C_o 2+ 150 mg, N_i 2+ 100 mg, (2+) 300 mg, M_o ~ 6 + 50 mg, C_d 2+ 30 mg, B_i ~ 3 + 30 mg, T_i ~ 210 mg, sb ~ (5+) 20 mg, A_s 3+ 30 mg, S_b 3+ 30 mg, V 2+ 20 mg and A_u 3+ 3 mg did not interfere with the assay, H 2 + and H 2 + were seriously disturbed. The method proposed that the sample should be pre-set at 500 ℃ for ignition and driven out. Compared with the titration medium of sulfuric acid, nitric acid, perchloric acid and sulfuric acid-citric acid, Wide, 0.6 ~ 2.1N end of the obvious, with sodium nitrite and starch as indicators, 0.05N sodium nitrite 6-8 drops is appropriate too much end point instability easy to fade, too little end dragging is not obvious. The standard silver recovery rate of 98.8 ~ 100.7%, with thiocyanate method, atomic absorption method were compared, the method is stable and fast. Analysis: 0.5 g sample, add concentrated nitric acid 15 ml, dissolved in low temperature for a few minutes, add 1: 3 sulfuric acid 10 ml, continue heating and dissolving and steaming to take thick white smoke 4 to 5 minutes. Cool, wash the watch glass and cup wall with water, the volume of the solution is controlled at 15-20ml, add 5ml of 10% citric acid, boil, cool to room temperature, add 6 drops of sodium nitrite (0.05N), 1 1% starch, potassium iodide standard solution (0.005N) titration to blue end point. With blank. The leaching residue after the sponge copper is leached with sulfuric acid contains 0.x-x% of silver. Using atomic absorption method, the error is larger. Measured by thiocyanate, mercury, copper, bismuth and non-ferrous metal ions are interference. Silver chloride precipitation with silver and copper and other interfering elements separated, and then sulfuric acid to remove chloride ions, long and tedious operation, and when the amount of silver is greater than 10 mg, part of the silver chloride aggregation, can not be completely decomposed by sulfuric acid, resulting in The result is low. This paper proposed in citric acid - sulfuric acid medium, iodometric method for rapid determination of silver, the method is stable and easy to operate.