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Recrystallization of Naphthalene

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MarkNY8679:
I am having problems with 2 questions from my lab

1)A sample od naphthalene, which should be white, was found to have a grayish color after the usual purification procedure, yet its melting point is correct, why the gray color--does this have anything to do with either the charcoal used in the recystallization process or impurities remaining even after purification?

2) Why is the final product from the crystallization process isolated by vacuum instead of gravity filtration--is this because the vacuum more efficiently removes the methanol used in recrystallization?

GSR:
If some orange or yellow color persists, wash your material with cold hexane.

Naphthalene sublimes readily.  it must be tightly capped when stored.

hope this is helpful.

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