Instead of using acetic anhydride, try propanoic anhydride. One extra carbon, makes it more fat soluble, crosses the blood brain barrier easier. This makes smack that is knock-out active at like 20mg and lasts 12+ hours. Heres a trade secret: use a tiny amount of sodium acetate as a catalyst to speed up this reaction. Making both acetic anhydride and propanoic anhydride are a lot easier than it seems. Get a pyrex and sprinkle it with 1/8" sodium bisulf*A*te, put this right up under your oven heating element set on broil. Keep going until it bubbles and a thin white film develops on the surface. If you see white vapor coming off you are heating it too much, although most ovens are perfect. When this is done let it cool, break it up and blend it into fine powder, leave it in the blender. This is sodium pyrosulfate. Calculate an equimolar amount of calcium proprionate (for propanoic anhydride) or calcium ethanoate (aka calcium acetate) (for acetic anhydride). Toss this in a blender with your sodium pyrosulfate and mix, then quickly pour it into a pyrex boiling flask. Toss this in a heated sandbath with either a distillation head or a heat-safe tube coming off it. Your anhydride will distill off easily with no side products. If you want to learn more check out my chemistry consulting on SR under "ron paul"