A sample of naphthalene, which should be pure white, was found to have a grayish color after the purification procedure. The melting point was correct but the melting point range was smaller. Why the gray color?
Is it possible the "purification procedure" included charcoal? Napthalene is normally purified by sublimation to prevent this.
Yes, it is indeed possible that the purification procedure included the use of charcoal, which could explain the grayish color. Naphthalene is typically purified by sublimation, a process in which the substance is heated to convert it directly from a solid to a vapor, bypassing the liquid state. This helps to remove impurities and obtain a pure white product.
However, if charcoal was involved in the purification process, it could have adsorbed impurities that affected the color of the naphthalene. Charcoal has a high adsorption capacity and can trap various substances, including colored impurities, through a process called adsorption. As a result, the naphthalene may have picked up some of these impurities, leading to the grayish color.
In this case, it is important to review the purification procedure and ensure that sublimation without the use of charcoal is employed to achieve the desired pure white color.