LACTIC ACID

n. La2k'ti2k. Lat., acidum lacticum. Fr., acide lactique. Ger., Milchsaure. A monobasic acid, C3H6O3, discovered by Scheele in 1780; hydroxy propionic acid. Various isomeric modifications of this formula are known: 1. Ordinary 1. a., 1. a. of fermentation, optically inactive ethyl i dene 1. a., the acidum lacticum of the U. S. Ph. (Fr., acide lactique; Ger., Milchsaure), CH3 CH(OH) COOH, a body derived from the fermentation of milk, and forming with water a sour, syrupy liquid, from which the acid can not be separated in a pure state. What is usually termed lactic acid is really a mixture of the anhydrides of the latter with a peculiar gum. the product of the lactic fermentation. Ordinary 1. a. is found in the gastric and intestinal juices, and, under certain circumstances, in the urine. The salts of ordinary 1. a. constitute the various lactates. L. a. has moderate soporific properties, and has been used as a solvent of diphtheritic false membranes. 2. Optically active ethyl i dene I. a., para lactic acid, sarcolactic acid (Ger., optisch active A ethyl i den-Milchsaure), a body closely resembling the former, and having the same structural composition, but differing in its power of rotating the polarized beam to the right. It occurs in the muscular juice, especially after a muscular contraction. 3. Ethylene I. a. (Ger., Aethylenmilchsdure), CH2OH CH, COOH, a sour, syrupy liquid occurring along with para lactic acid in the muscular juice. 4. Hydracrylic acid (q. v.). The 1. a's are a series of acids, CnHznOs. They comprise two isomeric groups, the normal 1. a's corresponding in constitution to the diatomic alcohols, and having the graphic formula co^OII ' an<* *^e i so lactic a's having the general ','(CnH!ta+l)20H formula C-j /, and being formed synthetically from ' nCOOH oxalic acid. CaH4Oal by a series of substitutions which are equivalent to replacing one atom of oxygen in the acid by two molecules of an alcohol radicle of the CnHsn series. [B, 2.] Fermentation 1. a. See ETHYL I DENE LACTIC ACID. L.-a. nitrate. Nitro lactic acid. [B.] [s. 565]