Asked by Gretchen

I was heating a flask containing salicylic acid, acetic anhydride, and H2SO4 to synthesize aspirin. During the heating period, a black sludge appeared at the bottom of the flask. I have no idea what this could be. Other students had experiments that worked just fine so there is nothing wrong with the reagents. What could this be?
Answered by DrBob222
It's a guess on my part but I suspect you used concd H2SO4 and that dehydrated something which left carbon as the black sludge. A second scenario is that the flask was dirty at the beginning of the experiment.