Organic acids refer to some organic compounds with acidity. The most common organic acid is carboxylic acid, and its acidity originates from carboxyl group (-COOH). Sulfonic acid (-SO3H), sulfonic acid (RSOOH), sulphur carboxylic acid (RCOSH) and so on are also organic acids. Organic acids can react with alcohols to produce esters.
Organic acids are soluble in water or ethanol, and are very acidic. They are not soluble in other organic solvents. Volatile or not. Precipitation of calcium, lead or barium salts insoluble in water can be achieved by adding calcium chloride or lead acetate or barium hydroxide solution into the aqueous solution of organic acids. These methods are often available if organic acids are removed from Chinese herbal extracts.