Choosing the appropriate extraction solvent is key to successfully isolating and purifying compounds.
The correct selection of extraction solvent should follow the following points:
(1) The extraction solvent is insoluble or almost insoluble in water;
(2) The solvent does not cause irreversible chemical reactions with the components in the mixture;
(3) The solubility of the extracted substance in the solvent is large, while the solubility of impurities and other components in the solvent is small;
(4) The boiling point of the extraction solvent should not be too high, and it can be easily removed from the solute by distillation and other methods.
In addition, the solvent's good chemical stability, low price, low toxicity, appropriate relative density, and ease of operation are also factors to consider. The choice of extraction solvent depends on the nature of the extract. Generally speaking, substances that are difficult to dissolve in water are extracted with petroleum ether, etc.; those that are more soluble are extracted with diethyl ether or toluene; substances that are easily soluble in water are extracted with ethyl acetate or other similar solvents. For example, using ether to extract oxalic acid from water is ineffective. If you use ethyl acetate instead, the effect will be better.
In fact, perfectly ideal solvents are difficult to find. As long as it meets the main requirements, it can be used even if there are some other shortcomings. Commonly used solvents include: ether, petroleum ether, pentane, hexane, carbon tetrachloride, chloroform, dichloromethane, dichloroethane, toluene, ethyl acetate, alcohol, etc.