Acetic Anhydride: Acetyl Chloride on Dry Sodium Acetate

Acetic anhydride is the acetylating agent that turns salicylic acid into aspirin. Gattermann (1914): melt the water out of sodium acetate, then drip acetyl chloride onto the dry salt in a retort and distil the anhydride off; redistil at 138 °C over a little more dry acetate. Yield about 50 g. Corrosive: goggles and gloves. The picture: acetic anhydride in a bottle (Wikimedia Commons).