I got it into my head that I wanted some glacial acetic acid, and went about the route of converting vinegar + baking soda to sodium acetate (wasn't the tri-hydrate, mp was above 120C), adding that to sulfuric acid, and distilling acetic acid from that. I used a large excess of sulfuric acid. The liquid I distilled, whatever it is, smells strongly of acetic acid, but won't freeze, even in the freezer. I'm thinking, maybe water got into it somehow, if perhaps that would lower the melting point below that of either water or acetic acid... or maybe some other contaminant? What could lower the mp below -15C? Oh, the temp at which it distilled was 115-125C (the range surprised me somewhat).
Could I, by some miracle, have created some acetic anhydride in this process? It has a mp of -73C... I thought it required oleum to do that, sulfuric acid wasn't strong enough... any tests I could perform to determine concentration and/or presence?