Lactic Acid (lak' tik as' id). Propanoic acid, 2-hydroxy-. Lactic acid[50-21-5]. » Lactic Acid is a mixture of lactic acid (C3H6O3) and lactic acid lactate (C6H10O5) equivalent to a total of not less than 88.0 percent and not more than 92.0 percent, by weight, of C3H6O3. It is obtained by the lactic fermentation of sugars or is prepared synthetically. Lactic Acid obtained by fermentation of sugars is levorotatory, while that prepared synthetically is racemic. [noteLactic Acid prepared by fermentation becomes dextrorotatory on dilution, which hydrolyzes l-()-lactic acid lactate to l-(+)-lactic acid. ] Packaging and storagePreserve in tight containers. LabelingLabel it to indicate whether it is levorotatory or racemic. IdentificationIt meets the requirements of the test for Lactate 191. Specific rotation 781A: between 0.05 and +0.05, for racemic Lactic Acid. Readily carbonizable substancesRinse a test tube with sulfuric acid, and allow to drain for 10 minutes. Add 5 mL of sulfuric acid to the test tube, carefully overlay it with 5 mL of Lactic Acid, and maintain the tube at a temperature of 15: no dark color develops at the interface of the two acids within 15 minutes. Residue on ignition 281: not more than 3 mg, from a 5-mL portion (0.05%). SugarsTo 10 mL of hot alkaline cupric tartrate TS add 5 drops of Lactic Acid: no red precipitate is formed. ChlorideTo 10 mL of a solution (1 in 100) acidified with nitric acid add a few drops of silver nitrate TS: no opalescence is produced immediately. SulfateTo 10 mL of a solution (1 in 100) add 2 drops of hydrochloric acid and 1 mL of barium chloride TS: no turbidity is produced. Heavy metals, Method II 231: 0.001%. Limit of citric, oxalic, phosphoric, or tartaric acidTo 10 mL of a solution (1 in 10) add 40 mL of calcium hydroxide TS, and boil for 2 minutes: no turbidity is produced. AssayTo about 2.5 mL of Lactic Acid, accurately weighed in a tared 250-mL flask, add 50.0 mL of 1 N sodium hydroxide VS, and boil the mixture for 20 minutes. Add phenolphthalein TS, and titrate the excess alkali in the hot solution with 1 N sulfuric acid VS. Perform a blank determination (see Residual Titrations under Titrimetry 541). Each mL of 1 N sodium hydroxide is equivalent to 90.08 mg of C3H6O3. Auxiliary InformationPlease check for your question in the FAQs before contacting USP.
USP35NF30 Page 3630 Pharmacopeial Forum: Volume No. 34(5) Page 1164 |