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测定铬铁矿中的亚铁,由于直接滴定法难以避免亚铁在溶矿过程中的氧化,因而采用预加氧化剂的间接滴定法-钒量法。此法已有人做过许多工作,并已应用于矿石分析。但关于该法的空白加热时间、钒(Ⅳ)在H_2SO_4-H_3PO_4介质中加热时的稳定性以及加热时间的影响等问题,各论不一。笔者按文献方法分析铬铁矿单矿物中亚铁时,发现测定结果随溶样加热时间长短而明显波动。为此,对钒量法进行了验证。试验表明,V_2O_5与VO_2的质量(m)比,即V_2O_5:VO_2在1:0.5～ 1:1.5之间,是钒(Ⅴ)和钒(Ⅳ)的相对稳定区,并以1:1时最为稳定;在H_2SO_4-H_3PO_4中,当VO_2:V_2O_5大于1.5:1时,随加热时间的延长,钒(Ⅳ)即明显地被氧化,且随VO_2
Determination of ferrous chromite, indirect titration method is difficult to avoid the oxidation of ferrous ore in the process of dissolution, which uses pre-oxidation of indirect titration method - vanadium amount method. This method has been done a lot of work, and has been applied to ore analysis. But the law of the blank heating time, vanadium (Ⅳ) in the H_2SO_4-H_3PO_4 medium heating stability and heating time issues such as the impact varies. When the author analyzed the ferrochromium single mineral ferrous iron according to the literature method, it was found that the determination result fluctuated obviously with the heating time of the sample. To this end, the amount of vanadium method was verified. The results show that the mass ratio of V 2 O 5 to VO 2 (V 2 O 5: VO 2) is relatively stable between vanadium (V) and vanadium (IV) at a ratio of 1: 0.5 to 1: 1.5. In the H_2SO_4-H_3PO_4, when VO_2: V_2O_5 is greater than 1.5: 1, the vanadium (Ⅳ) is obviously oxidized with the increase of heating time,