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A sample of naphthalene which should be pure white!

Naphthalene is a white, crystalline solid.

It melts at 26 degrees Celsius and boils at 235 degrees Celsius.

In this blog post, we will discuss how to test whether naphthalene is pure white by using two different approaches:

  1. The melting point method 
  2. The solubility in the benzene method.
graphene, graphite, benzene @ Pixabay

The melting point method is a qualitative test to identify whether an unknown substance is naphthalene.

Pure white crystals of this compound melt at 26 degrees Celsius and are not soluble in benzene.

This means that the melting point of pure white samples should be around 26 degrees Celsius.

While impure ones will have higher values or they won’t melt at all.

For example, if we heat up a sample with brownish coloration until it melts then cools back down again.

There should still be some residual solid left on the inside surface because it didn’t completely dissolve.

Like pure naphthalene does when heated and cooled rapidly enough (within seconds). 

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