Determination of End Point in Benzoic Acid Crystallization via Laser Irradiation

IF 2.5 3区 教育学 Q2 CHEMISTRY, MULTIDISCIPLINARY Journal of Chemical Education Pub Date : 2024-08-05 DOI:10.1021/acs.jchemed.4c0043710.1021/acs.jchemed.4c00437
Liying Dong, Yun He and Zunting Zhang*, 
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Abstract

The recrystallization experiment is a significant component of chemistry laboratory instruction in both middle schools and universities. The method for identifying the crystallization end point is absent from the textbooks. In this paper, the characteristic of light propagation in nonuniform media was employed to identify the crystallization end point. Filter the crude benzoic acid solution while it is hot, allowing the laser beam to pass through the center of the filtrate. Observe the alteration in the light spot projected onto the white screen through the beam. As the concentration gradient of the solution changes, the gradual recovery of the light spot from the reticulated stripes of light and dark indicates completion of the crystallization process, signaling readiness for the subsequent filtration experiment. This method offers a simple means to determine the end point of crystallization, and the phenomenon is intuitive, making it suitable for chemistry teaching experiments.

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通过激光照射确定苯甲酸结晶的终点
再结晶实验是中学和大学化学实验教学的重要组成部分。教科书中没有确定结晶终点的方法。本文利用光在非均匀介质中传播的特性来确定结晶终点。趁热过滤粗苯甲酸溶液,让激光束穿过滤液中心。观察通过光束投射到白色屏幕上的光斑的变化。随着溶液浓度梯度的变化,光点从明暗网状条纹中逐渐恢复,表明结晶过程已经完成,为随后的过滤实验做好了准备。这种方法提供了确定结晶终点的简单手段,而且现象直观,适合化学教学实验。
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来源期刊
Journal of Chemical Education
Journal of Chemical Education 化学-化学综合
CiteScore
5.60
自引率
50.00%
发文量
465
审稿时长
6.5 months
期刊介绍: The Journal of Chemical Education is the official journal of the Division of Chemical Education of the American Chemical Society, co-published with the American Chemical Society Publications Division. Launched in 1924, the Journal of Chemical Education is the world’s premier chemical education journal. The Journal publishes peer-reviewed articles and related information as a resource to those in the field of chemical education and to those institutions that serve them. JCE typically addresses chemical content, activities, laboratory experiments, instructional methods, and pedagogies. The Journal serves as a means of communication among people across the world who are interested in the teaching and learning of chemistry. This includes instructors of chemistry from middle school through graduate school, professional staff who support these teaching activities, as well as some scientists in commerce, industry, and government.
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