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全日制十年制学校初中课本(全一册)增加了《纸上层析》的演示实验,高中课本第一册规定了《阿佛加德罗常数测定》的实验项目。在教学中,一般地按教本去做,前者往往达不到预期效果,后者有时结果误差较大。现将怎样做好这两个实验的一些体会写在下面,与中学化学教师共同讨论。一、纸上层析原理: 纸上层析是色层分析的一种。它是以溶有试样的溶剂(水)点样于滤纸上作为固定液相;用另一种互不相溶(或部分互溶)的溶剂(也叫展开剂)作为流动相。当展开剂在滤纸毛细管作用下,从一端扩散到另一端时,点样中的各组分由于在这两种溶剂中的溶解度不同,而以不同速度向前展开,从而使各组分得到分离。
Full-time 10-year school junior high school textbooks (all one) added a “paper chromatography” demonstration experiment, high school textbooks book “Avergardiro constant determination” pilot project. In teaching, generally according to the textbook to do, the former often fail to achieve the desired effect, the latter sometimes larger error. Now how to do some of the experience of these two experiments written below, and high school chemistry teachers to discuss. First, the paper chromatography principle: Paper chromatography is a kind of color analysis. It is dissolved in the sample solvent (water) dotted on the filter paper as a fixed liquid; with another immiscible (or partially miscible) solvent (also known as the developer) as the mobile phase. As the developer expands from one end to the other under the capillary action of the filter paper, the components in the spot are separated forward due to different solubilities in the two solvents and at different velocities .