The citric acid of lemons, the tartaric acid of grapes, benzoic, cinnamic, salicylic, tannic acid, and some of their salts are of interest pharmacologically. Glycyrrhizin, the sweet principle of glycyrrhiza (licorice), is really glycyrrhizic acid, and is sweet to the taste only in the form of alkaline salts. It is precipitated and rendered tasteless by acids.