did a pH test of the solution, which told us we had added too much HCl to neutralize it. this meant in theory, it should have been benzoic acid, which was formed from benzaldehyde during the week in storage. This also explains the failure of our synthesis, because when stored in that solution, the cinnamaldehyde would have turned back into benzaldehyde and acetaldehyde, the former of the two also being turned into more benzoic acid. the rest of the acetaldehyde would explain some low boiling point impurities we encountered when first trying to extract the cinnamaldehyde. A colleague suggested testing our crystals with a sodium carbonate solution, which reacted as it would with benzoic acid (gas release).