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How to choose chemical reagents

During the experiment, according to the requirements of the experiment, such as the sensitivity and selectivity of the analytical method, the content of the analytical object and the requirements for the accuracy of the analytical results, the chemical reagents of the corresponding level should be reasonably selected. Since the price of the same reagent of different specifications varies greatly, under the premise of meeting the experimental requirements, the level of the selected reagent should be low or high, so as to avoid waste. The selection of reagents should consider the following points:
1. Standard solutions commonly used in titration analysis are generally used first. R. The reagents are roughly prepared, and then calibrated with working reference reagents. In experiments that do not require very high analysis results, G. R. or A. R. Reagents replace working reference reagents. Other reagents used in titration analysis are generally of analytical grade.
2. In terms of bulk content, G. R. and A. R is the same or similar, but the impurity content is different. If the experiment has high requirements on the main content of the reagents used, such as constant chemical analysis, A. R. Reagents; if the requirements for the impurity content of the reagents are strict, G. R. reagents.
3. Instrumental analysis experiments generally use G. R.A. R. Or special reagents, high-purity reagents should be used when measuring trace components.
4. If the purity of the existing reagent cannot meet certain experimental requirements, it is often used after one or more purifications. Commonly used purification methods are distillation (liquid reagent) and recrystallization (solid reagent).
5. Organic chemistry experiments are inseparable from organic solvents and reagents. Solvents are not only used as reaction media, but also often used in product purification and post-processing. Commercially available organic solvents and reagents are available in various specifications such as industrial grade, chemical grade and analytical grade. The higher the purity, the more expensive the price.
In organic synthesis, solvents and reagents of appropriate specifications are often selected according to the characteristics and requirements of the reaction, so that the reaction can proceed smoothly. Some organic reactions have higher requirements on solvents and reagents, and even the presence of trace impurities or moisture will affect the rate, yield and even success or failure of the reaction. Therefore, it is also very important to understand the properties of solvents, reagents and purification methods commonly used in organic reactions.