自动电位滴定法测定铬矿石中三氧化二铬  

Determination of chromium oxide in chrome ores by automatic potentiometric titrimetry

作　　者：邓川[1] 马德起[1] 

机构地区：[1]天津出入境检验检疫局化矿金属材料检测中心,天津300456

出　　处：《冶金分析》2013年第12期62-66,共5页Metallurgical Analysis

摘　　要：采用Na2O2将样品在800℃下熔融,加入H2SO4和H3PO4溶解、(NH4)2S2O8氧化后,建立了(NH4)2Fe(SO4)2还原-KMnO4返滴定法测定铬矿石中Cr2O3含量的自动电位滴定法。对电极和滴定参数进行了研究,并考察了影响滴定终点判断的多种因素。最终确定213型铂电极作为指示电极;(NH4)2Fe(SO4)2和KMnO4标准溶液标定时信号漂移选择15mV/min,加液速度分别为10mL/min和最大值,等当点识别标准分别为80和70;样品反滴定时信号漂移选择20mV/min,加液速度为最大值,等当点识别标准为70。采用方法对铬矿石标准物质GBW07201和GBW07202进行测定,其相对标准偏差(RSD,n=10)为0.14%和0.09%,与认定值相对误差为0.04%和0.06%。将方法用于不同产地的铁矿石实际样品中三氧化二铬的测定,结果与国标方法GB/T 24230-2009基本一致。Chrome ore samples were melted by Na2O2 at 800℃, dissolved by H2SO4 and H3PO4 , then oxidized by （NH4）2 S2O8. Then, a method for determination of Cr2 O3 in chrome ore was developed by automatic potentiometric titrimetry with （NH4）2 S2 O8 reduction-KMnO4 back titration. The electrodes and titration parameters were investigated, and the various factors affecting the determination of the titration end point were discussed. Finally, 213 type Pt electrode was selected as indicator electrodeL （NH4）2Fe（SO4）2 and KMnO4 standard solution were calibrated respectively with signal drift as 15 mV/min, the speed for adding liquid as 10 mL/min and the maximum and recognition criteria of e- quivalent point as 80 and 70; the sample was back titrated with signal drift as 20 mV/min, the speed for adding liquid as the maximum and recognition criteria of equivalent point as 70. The method was applied to determination of chromium ore certified reference materials GBW07201 and GBW07202. The relative standard deviations （RSD, n=10） were 0.14% and 0.09G, respectively, and the rela- tive errors were 0.04% and 0.06 % respectively compared with the certified values. The method was applied to determination of chromium oxide in actual chromium ore samples from different producing areas, and the results were consistent with those obtained by national standard method GB/T 24230- 2009.

关 键 词：铬矿石 三氧化二铬 自动电位滴定法 碱熔 

分 类 号：O655.2[理学—分析化学]