19。 According to medical encyclopedia official website, the polarity of acetic anhydride is 19. Acetic anhydride alias acetic anhydride; Acetic anhydride; Acetic anhydride; Anhydrous acetic acid. Appearance and properties are colorless and transparent liquid with pungent smell (similar to acetic acid), and its vapor is tear gas. Acetic anhydride is mainly used as acetylation reagent, as well as in the manufacture of drugs, dyes, cellulose acetate, initiators, bleaches and so on.