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滴定分析终点误差的计算是分析教学中的一个非常重要的内容,通过终点误差的计算可以对滴定方法的准确度、指示剂的选择等做出评价。目前,国内几乎所有的分析化学教科书在介绍终点误差的计算时都直接采用了Ringbom公式。与此同时,国内的许多科学工作者对Ringbom公式进行相应的改进,并试图将其拓展到四大滴定分析中。然而,与此形成鲜明对照的是,国外的分析化学教材中却基本不提及Ringbom公式。本文对终点误差的计算公式进行了探讨。我们指出,(1)Ringbom公式在建立过程中采用了不恰当的基准,同时采用了近似处理,这使得它仅仅是一个近似公式,因而不应当对其有过度的倚重;(2)Ringbom公式向四大滴定的拓展值得商榷。我们建议,应该从终点误差的定义出发,以滴定终点体积比和化学计量点的体积比为基础,建立合理、准确和简洁的终点误差计算公式。
Titration Analysis The calculation of the end point error is a very important part of the analytical teaching. The accuracy of the titration method and the choice of indicator can be evaluated by calculating the end point error. At present, almost all the analytical chemistry textbooks in the country use the Ringbom formula directly when introducing the calculation of the end point error. In the meantime, many scientists in our country have made corresponding improvements to the Ringbom formula and have tried to extend it to the four major titration analyzes. However, in stark contrast, there is no reference to the Ringbom formula in analytical chemistry textbooks abroad. In this paper, the calculation formula of the end point error is discussed. We point out that (1) the Ringbom formula uses an inappropriate datum in the process of its establishment, and the approximation process is used at the same time, which makes it an approximation formula and should not be overly relied upon. (2) The expansion of the four titration is debatable. We suggest that a reasonable, accurate and concise end point error formula should be established based on the definition of the end point error based on the volumetric ratio of titration end point volume ratio and stoichiometric point.