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So I had a lab where I separated caffeine from tea with methylene chloride. The caffeine I was left with had a melting point of 225.2-226.8*C and the book said the melting point of caffeine is 237.8*C. Does that mean that I have an impure product or that I didn't get caffeine?
It could mean either, honestly. What do you mean by “didn't get caffeine”? I suppose you could have ended up with the rest of the tea product. You'd have to know the melting point of the tea without the caffeine to really know whether that's what you were looking at.