lactose (lak'tos)

Syn.: milk sugar, galactosaccharum, saccharum lactis. C12- H22O11+H2O, a compound carbohydrate (hexobiose) present in milk; also present at times in the urine of pregnant women. Upon hydrolysis with dilute acids or lactase one molecule of 1. is converted into one molecule of d. -glucose and one molecule of d.-galactose. It responds to the ordinary reduction tests, which are characteristic of glucose, such as the Fehling test, Nylander's test, etc. But it will not ferment with yeast cells, a property which is made use of to distinguish it from glucose. With phenyl hydra zin it forms a crystalline phenyl-lac to saz one. [Lat., lac, milk.]