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本文采用偶氮氯膦Ⅲ比色法,测定硬质合金中微量稀土元素,並对其主体元素钨、钼、钛、钴、钽和铌等在测定条件下的行为进行了研究。试验结果表明,以硝酸、氢氟酸分步分解试样,用氟化铵代替氢氟酸沉淀稀土元素而与共存元素分离,可避免钴的共沉淀。方法易于掌握,有较高的准确度和精密度。对三个试样(其稀土含量在0.09～5%范围内),由不同分析人员以该法进行了80余次单次测定,相对偏差为11～5%。主要试剂盐酸-柠檬酸钠缓冲溶液(pH=2);偶氮氯膦Ⅲ溶液—0.02%,乙醇(8+92)溶液;混合稀土标准溶液(10微克/毫升)—按Y∶La∶Ce=50:
In this paper, the determination of trace rare earth elements in cemented carbides by chlorophosphonazo Ⅲ colorimetric method and the behavior of the main elements of tungsten, molybdenum, titanium, cobalt, tantalum and niobium in the determination conditions were studied. The experimental results show that the co-precipitation of cobalt can be avoided by using nitric acid and hydrofluoric acid to decompose the sample in stages and using ammonium fluoride instead of hydrofluoric acid to separate the rare earth elements from the coexisting elements. The method is easy to grasp, with high accuracy and precision. Three samples (the content of rare earth in the range of 0.09 ~ 5%), by different analysts to the law more than 80 times a single determination, the relative deviation of 11 to 5%. The main reagents hydrochloric acid - sodium citrate buffer solution (pH = 2); chlorophosphonazo Ⅲ solution -0.02%, ethanol (8 +92) solution; mixed rare earth standard solution (10 micrograms / ml) = 50: