自动电位滴定法测定铬铁中铬含量的不确定度评定

摘要

建立了自动电位滴定法测定铬铁中铬含量的数学模型，对数学模型中各个参数进行不确定度来源分析，分别对A类不确定度及B类不确定度进行评定，对各不确定度分量进行合成，得到铬质量分数的不确定度。当铬铁中铬含量为68.31%时，扩展不确定度为0．52％（k=2）。结果表明玻璃器具的精度、自动电位滴定仪自带体积管的误差、自动电位滴定仪终点识别的误差是测量不确定度的主要来源。%A mathematics model for evaluating the uncertainty for the determination of chromium in ferrochromium by automatic potentiometric titration was established. The uncertainty sources for each of the parameters in the model were analyzed. The uncertainties of type A or type B were evaluted. According to the method,the component uncertainties were synthesized, which were used to obtain the uncertainty evalution. The expanded uncertainty was 0.52%(k=2) as chromium content in errochromium was 0.52%.The results showed that the accuracy of glassware, inaccuracy from prover of automatic potentiometric titration and error from end identification were the main sources for uncertainties.