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课本中《酚醛树脂的制取》实验中生成的酚醛树脂不能取出，学生不能直接触摸感觉其硬度，且试管加入乙醇也不易洗净。 我们将实验进行改进可避免上述不足，方法如下。 其装置仍按课本所述，只不过在有导管的胶塞上穿一根下端弯成勾状的铜丝。其长度伸到反应物液面下，按课本所?
The phenolic resin produced in the textbook “Preparation of Phenolic Resins” cannot be removed. The students cannot directly feel the hardness of the phenolic resin, and the tube is not easy to wash with ethanol. We will improve the experiment to avoid the above deficiencies as follows. The device is still described in the textbook, except that a copper plug with a hook bent at the lower end is worn on a rubber plug with a conduit. Its length reaches the liquid surface of the reactants, according to the textbook?