Naphthalene, as a polycyclic aromatic hydrocarbon, plays an irreplaceable and unique role in fine chemicals, mainly used in the production of fuels, pharmaceuticals, tanning agents, fragrances, plant protectants, and rubber anti-aging agents. This study uses tar industrial naphthalene as raw material and uses the melting method in the static crystallization method to prepare refined naphthalene. The experimental results show that this process has the advantages of simple operation, low energy consumption, no need for solvents, and low emissions of three wastes; When the crystallization temperature is 78.5 ℃, the crystallization time is 20 hours, the cooling rate is 2 ℃/h, and the constant temperature time is 16.5 hours, the purity of refined naphthalene is as high as 98.21%. Therefore, this study has important theoretical significance and practical value.

1.2 1实验步骤

1.2 1 Experimental Steps

将工业萘加热至85℃，全部熔融后装入结晶器内。将结晶器水套（超级恒温水浴）温度升高，控制在85℃。恒温30分钟后开始以一定的降温速度进行降温。当达到所需要的温度后继续进行恒温。若干小时后开始放出液体，装入接受瓶内。然后再继续升温升至85℃，将剩余物料放出，装入另一个接受瓶内，进行熔点测定。

Heat industrial naphthalene to 85 ℃, melt all of it, and then load it into a crystallizer. Raise the temperature of the crystallizer water jacket (super constant temperature water bath) to 85 ℃. After a constant temperature of 30 minutes, start cooling at a certain rate. After reaching the required temperature, continue to maintain a constant temperature. After a few hours, the liquid begins to be discharged and loaded into the receiving bottle. Then continue to raise the temperature to 85 ℃, release the remaining materials, and put them into another receiving bottle for melting point measurement.

1.3.2测定熔点的步骤

1.3.2 Steps for determining melting point

1.将热台放置在显微镜底座上，并使放入盖玻璃片的端口位于右侧。

1. Place the hot stage on the microscope base with the port for placing the cover glass on the right side.

2.取两片盖玻片（干净、干燥的），在一片上放适量的待测物品（不大于0.1mg），并使药品均匀分布，盖上另一片载玻片，轻轻压实，然后放置在热台中心，盖上隔热玻璃。

2. Take two cover glass slides (clean and dry), place an appropriate amount of the test item (not more than 0.1mg) on one slide, and evenly distribute the drug. Cover the other slide with glass, gently compact it, and then place it in the center of the hot bench, covered with insulation glass.

3.调整好显微镜，直到目镜中能清晰看到热台中待测物体的象为止。

3. Adjust the microscope until the image of the object to be tested in the thermal stage can be clearly seen in the eyepiece.

4.打开电源开关，仪表上显示出热台的即时温度值。将开关拨向自动控制。

4. Turn on the power switch and the instrument will display the real-time temperature value of the heating table. Turn the switch to automatic control.

5.观察被测物料的熔点过程，纪录初熔和全熔时的温度值，用镊子取下隔热玻璃和盖玻片，即完成测试。

5. Observe the melting point process of the tested material, record the temperature values at initial and full melting, and use tweezers to remove the insulation glass and cover glass to complete the test.

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