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一般分析高铬时,尤其是对高温耐热镍基含钨合金中高铬的测定,常采用硝酸、盐酸混酸溶样(或者以硫磷混酸溶样),硫磷酸冒烟,在硝酸银存在下,用过硫酸铵将铬氧化为六价,也有的是在王水溶样后,再加高氯酸将铬氧化,然后,以亚铁盐进行还原滴定。对于大批生产或炉前分析来说,前者时间太长,后者,经高氯酸氧化后有钨酸析出,容易不稳。鉴于热浓高氯酸的强氧化性,本方法采用高氯酸磷酸溶样,在试样溶解的同时,以磷酸络合钨,形成可溶性络合物H_3PO_4·12WO_3而存在于溶液中,试样溶解后,高
General analysis of high chromium, especially for high-temperature heat-resistant nickel-based tungsten alloy high chromium determination, often using nitric acid, hydrochloric acid mixed acid sample solution (or phosphoric acid mixed solution), sulfur phosphoric acid smoke in the presence of silver nitrate , With ammonium persulfate oxidation of chromium into hexavalent, but also in aqua regia samples, coupled with perchlorate oxidation of chromium, and then, ferrous salt reduction titration. For a large number of production or pre-furnace analysis, the former time is too long, which, after perchloric acid oxidation of tungstic acid precipitation, easy to instability. In view of the strong oxidizing power of perchloric acid, the present method uses phosphoric acid perchloric acid to dissolve the sample, while the sample is dissolved, the complex is formed by complexing tungsten with phosphoric acid to form the soluble complex H_3PO_4 · 12WO_3, and the sample After dissolving, high