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在电流滴定中根据被测物质与滴定剂在电极上氧化还原性质不同而呈现出4种类型的滴定曲线,见图1。在理论上,前三类曲线的转折点就是滴定等当点。据此,由折点的x坐标(滴定剂体积)即可准确地计算出被测物的含量。而且,如果情况真如理想曲线(实线)所示,只要发现电解池电流突然转向,就可定为滴定终点以实现自动控制。但事实上由于各种因素的影响,不可能得到这种理想曲线,而是形成如图1中虚线所示的曲线。特别不利的是当滴定到转折点附近时没有明显突跃而是渐变,这给直接测定带来困难。加之各测量点又不是严格地与直线吻合而是有一定的误差,所以人们通常用作图法来解决。但这种办法费时,精度有限,影响了电流滴定法的应用。本文提出用PC—1500袖珍计算机自动完成判定滴定终点,精度高,操作简单、快速。本程序同样可用于电位和电导等滴定法中。
In the current titration, there are 4 types of titration curves according to the redox properties of the test substance and the titrant on the electrode, as shown in FIG. 1. In theory, the turning point of the first three curves is the titration point. Accordingly, from the turning point of the x-coordinate (titrant volume) can accurately calculate the content of the measured object. Also, if the situation is as the ideal curve (solid line) shows, as soon as the cell current is suddenly turned, it can be titrated to the end point for automatic control. But in fact due to various factors, it is impossible to get this ideal curve, but to form the curve shown in Figure 1, the dotted line. It is particularly disadvantageous that there is no noticeable jump but a gradual change when titling to the vicinity of the inflection point, which renders direct determination difficult. Coupled with the measurement point is not strictly consistent with the line but there is a certain error, so people are usually used to solve the map method. However, this method is time-consuming and has limited accuracy, which affects the application of the current titration method. This paper proposes to use the PC-1500 pocket computer to automatically determine the titration end point, high precision, easy to operate and fast. This procedure can also be used for potentiometry and conductivity titration method.