[Aisha_18]

why would napthalene be grey after recrystallization even If the melting range was small and correct.

I was thinking impurites, but that would have affected the metling range which was the same as if it was the usual pure white. I really cant think of anything else.

[renge ishyo]

What was your melting point range? The melting point for crude napthalene is about 78^oC while truly pure napthalene is slightly higher at 80^oC. From the color at least it seems like you have isolated crude napthalene. See the wiki for details on the impurities in the production section: http://en.wikipedia.org/wiki/Naphthalene

[UnintentionalChaos]

why would napthalene be grey after recrystallization even If the melting range was small and correct.

I was thinking impurites, but that would have affected the metling range which was the same as if it was the usual pure white. I really cant think of anything else.

There are times when compounds melt at their literature values, but are still discolored. Prime examples are any kind of iodinated organic, polyphenolic compounds, etc. In these cases, it is to be assumed that the discoloring is from a very strongly colored contaminant that is only present in small quantites.

If you want to recrystallize again, do so from boiling 50:50 ethanol:water, which gave me glittering white crystals from over-the-counter mothballs. They smell distinctly different (cleaner and more pleasant, if naphthalene can be called pleasant) from the crude product, which was claimed 98-99% pure already.

[lmlh]

i think you got the desired pure compound because we cann't say anything from the color
even the same compound have different color in different crystal state .