I took the melting point on some recrystallized lidocaine for a lab recently and got a range (55-56 oC) 13 oC below the lit value (68-69 oC). This is, I think, the second time in a couple years of lab I've gotten a product with a substantially lower MP than lit values, but with a very tight melting range (almost instantaneous, and the bulb was not turned up very hot). Is the only logical explanation for this that I obtained a different product? It would be confusing if this is the case because I obtained a decent MP range for my previous product, and there's essentially only one type of reaction that could take place in the following step.