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實驗步驟

1.2 1 Experimental Steps

將工業(yè)萘加熱至85℃，全部熔融后裝入結(jié)晶器內(nèi)。將結(jié)晶器水套（超級恒溫水?。囟壬?，控制在85℃。恒溫30分鐘后開始以一定的降溫速度進行降溫。當(dāng)達到所需要的溫度后繼續(xù)進行恒溫。若干小時后開始放出液體，裝入接受瓶內(nèi)。然后再繼續(xù)升溫升至85℃，將剩余物料放出，裝入另一個接受瓶內(nèi)，進行熔點測定。

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測定熔點的步驟

1.3.2 Steps for determining melting point

1.將熱臺放置在顯微鏡底座上，并使放入蓋玻璃片的端口位于右側(cè)。

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

2.取兩片蓋玻片（干凈、干燥的），在一片上放適量的待測物品（不大于0.1mg），并使藥品均勻分布，蓋上另一片載玻片，輕輕壓實，然后放置在熱臺中心，蓋上隔熱玻璃。

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.調(diào)整好顯微鏡，直到目鏡中能清晰看到熱臺中待測物體的象為止。

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.打開電源開關(guān)，儀表上顯示出熱臺的即時溫度值。將開關(guān)撥向自動控制。

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.觀察被測物料的熔點過程，紀(jì)錄初熔和全熔時的溫度值，用鑷子取下隔熱玻璃和蓋玻片，即完成測試。

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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