精萘是一种常见的化工原料，在工业生产中有特定用途，准确识别它需要结合其物理性质、化学特性等多方面特征。掌握科学的识别方法，能避免与其他类似物质混淆，确保在使用或处理时的安全性。

　　Naphthalene is a common chemical raw material with specific applications in industrial production. Accurately identifying it requires a combination of its physical properties, chemical characteristics, and other characteristics. Mastering scientific identification methods can avoid confusion with other similar substances and ensure safety during use or handling.

　　从外观和形态入手是初步识别的基础。精萘通常呈现为白色或微黄色的片状晶体，表面光滑，具有一定的光泽，质地较脆，用手指轻轻一捻就容易破碎成细小的颗粒。如果观察到的物质是块状、粉末状，或者颜色明显偏深（如棕色、黑色），则大概率不是精萘。另外，精萘晶体的边缘较为规整，在自然光下观察，会有轻微的油亮感，这是其晶体结构带来的特征，与其他白色晶体（如食盐、蔗糖）的外观有明显区别 —— 食盐颗粒更细小且呈立方体，蔗糖则多为颗粒状或粉末状，没有精萘的片状形态。

　　Starting from appearance and form is the foundation for initial identification. Refined naphthalene usually appears as white or slightly yellow plate-like crystals, with a smooth surface and a certain luster. Its texture is relatively brittle, and it can easily break into small particles with a gentle twist of the finger. If the observed substance is in the form of blocks, powders, or has a significantly darker color (such as brown or black), it is highly likely not naphthalene. In addition, the edges of refined naphthalene crystals are relatively regular, and when observed under natural light, there is a slight oily luster, which is a characteristic brought by its crystal structure. It is significantly different from the appearance of other white crystals (such as salt and sucrose) - salt particles are smaller and more cubic, while sucrose is mostly in the form of granules or powders, without the sheet-like form of refined naphthalene.

　　气味是识别精萘的重要线索。精萘具有独特的、略带刺激性的气味，这种气味类似于卫生球（樟脑丸），但更为浓烈和纯粹。将少量物质放在密封容器中，稍等片刻后打开容器，若能闻到这种特殊气味，可作为识别的参考之一。不过需要注意的是，长时间吸入这种气味可能会对人体产生不适，因此闻气味时应保持距离，避免直接大量吸入。同时，有些物质可能会人工添加类似气味来冒充精萘，所以不能仅凭气味就下结论，需要结合其他特征综合判断。

　　Odor is an important clue for identifying naphthalene. Naphthalene has a unique and slightly irritating odor, similar to that of sanitary balls (mothballs), but more intense and pure. Place a small amount of substance in a sealed container, wait for a moment, and then open the container. If you can smell this special odor, it can be used as one of the identification references. However, it should be noted that inhaling this odor for a long time may cause discomfort to the human body. Therefore, when smelling the odor, one should maintain a distance and avoid inhaling a large amount directly. At the same time, some substances may be artificially added with similar odors to impersonate naphthalene, so conclusions cannot be drawn solely based on odor, and other characteristics need to be comprehensively judged.

　　熔点测试能进一步确认精萘的身份。精萘有固定的熔点，大约在 80.5℃左右。可以采用简单的熔点测试方法：取少量待检测物质放在干净的金属片上，用小火缓慢加热金属片，观察物质的熔化情况。如果物质在 80℃左右开始熔化，且熔化过程较为均匀，没有明显的杂质残留或分层现象，那么很可能是精萘。若熔化温度明显低于或高于这个范围，或者熔化时出现冒泡、变色等异常情况，则说明该物质不是精萘。测试时需注意控制加热速度，避免温度上升过快导致判断失误，同时做好防火措施，因为精萘具有易燃性。

　　Melting point testing can further confirm the identity of refined naphthalene. Naphthalene has a fixed melting point, around 80.5 ℃. A simple melting point testing method can be used: take a small amount of the substance to be tested and place it on a clean metal sheet, slowly heat the metal sheet with low heat, and observe the melting of the substance. If the substance begins to melt at around 80 ℃ and the melting process is relatively uniform without obvious impurities or delamination, it is likely to be refined naphthalene. If the melting temperature is significantly lower or higher than this range, or if there are abnormal conditions such as bubbling or discoloration during melting, it indicates that the substance is not refined naphthalene. During testing, attention should be paid to controlling the heating speed to avoid rapid temperature rise and judgment errors. At the same time, fire prevention measures should be taken, as refined naphthalene is flammable.

　　溶解性实验也能辅助识别。精萘在有机溶剂中的溶解性有一定特点，它易溶于苯、甲苯、乙醚等有机溶剂，而在水中的溶解度非常小，几乎不溶解。可以取少量待检测物质，分别加入水和苯中，观察溶解情况。若在水中基本不溶，而在苯中能较快溶解，且溶液呈现透明状，则符合精萘的溶解性特征。如果在水中能溶解，或者在苯中溶解后溶液浑浊、有沉淀，就可以排除是精萘的可能。进行溶解性实验时，要注意使用少量试剂，并且在通风良好的环境中操作，因为所用到的有机溶剂大多具有挥发性和一定的毒性。

　　Solubility experiments can also assist in identification. The solubility of refined naphthalene in organic solvents has certain characteristics. It is easily soluble in organic solvents such as benzene, toluene, and ether, while its solubility in water is very small and almost insoluble. You can take a small amount of the substance to be tested and add it separately to water and benzene to observe its dissolution. If it is basically insoluble in water but can dissolve quickly in benzene, and the solution appears transparent, it conforms to the solubility characteristics of naphthalene. If it can dissolve in water, or if the solution becomes turbid and precipitates after dissolving in benzene, the possibility of refined naphthalene can be ruled out. When conducting solubility experiments, it is important to use a small amount of reagents and operate in a well ventilated environment, as most of the organic solvents used are volatile and toxic.

　　化学特性反应可作为最终确认的依据。精萘具有芳香烃的一些化学性质，比如在浓硫酸的作用下，会发生磺化反应。取少量待检测物质，加入适量浓硫酸，轻轻振荡后观察，若溶液呈现黄色或棕色，且有轻微的放热现象，说明可能发生了磺化反应，这与精萘的化学特性相符。另外，精萘在空气中燃烧时，会产生明亮的火焰，并且伴有黑烟，这是因为其含碳量较高，燃烧不充分导致的，这一燃烧特征也可作为识别的参考，但进行燃烧实验时必须在安全的环境中进行，远离易燃物，防止发生火灾。

　　Chemical characteristic reactions can serve as the basis for final confirmation. Naphthalene has some chemical properties of aromatic hydrocarbons, such as sulfonation reaction under the action of concentrated sulfuric acid. Take a small amount of the substance to be tested, add an appropriate amount of concentrated sulfuric acid, gently shake and observe. If the solution appears yellow or brown and there is a slight exothermic phenomenon, it indicates that a sulfonation reaction may have occurred, which is consistent with the chemical properties of refined naphthalene. In addition, when refined naphthalene burns in the air, it produces bright flames accompanied by black smoke due to its high carbon content and insufficient combustion. This combustion characteristic can also be used as a reference for identification, but combustion experiments must be conducted in a safe environment, away from flammable materials, to prevent fires.

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