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用置换法测定金属当量,是无机化学实验的重要内容之一,但该实验采用的仪器装置还待改进。如有的装置(见图1a,下称装置a)接头多、准备较费时、有漏气的可能等等。也有的装置(见图1b,下称装置b)虽然简单、不易漏气,但需要特制的量气管(不能用碱式滴定管代替),而且较难操作。诸如,要用尼龙线系住折叠的金属片;量气管中先加入的酸与后加入的蒸馏水要避免混合;要用拇指紧堵管口,并迅速倒转量气管于装有水的烧杯中,等等。笔者提出一种改进的仪器装置(见图1c,下称装置c)供教学参考。
The determination of the metal equivalent by displacement method is one of the important contents of inorganic chemistry experiments, but the apparatus used in this experiment needs to be improved. If any device (see Figure 1a, hereinafter referred to as device a) has more connectors, it is more time-consuming to prepare, there is the possibility of leaks, and so on. Other devices (see Figure 1b, hereinafter referred to as device b), which are simple and not easy to leak, require special measuring tubes (which cannot be replaced by basic burettes) and are difficult to handle. For example, use a nylon thread to tie the folded metal sheet; the acid to be added first in the gas tube and the distilled water to be added later should be avoided; use the thumb to close the tube and quickly invert the tube to a beaker filled with water. and many more. The author proposes an improved instrument device (see Fig. 1c, hereinafter referred to as device c) for teaching reference.