UREA, in chemistry. The nature and properties of urea have been chiefly investigated by Fourcroy arid Vauquelin. It is obtained from urine. It may be ex tracted by the following process : If a quantity of huMan urine, which has been passed a few hours after taking food, be evaporated with a gentle heat, to the con sistence of a thick syrup, and allowed to cool, it concretes into a crystalline mass. Add to this mass, in separate portions, four times its weight of alcohol ; with the application of a gentle heat, great part is dissolved, and what remains consists of different saline substances. Separate the solution from the undissolved part, and introduce it into a retort. Distil with the heat of a sand bath, and continue the boil ing till the liquid is reduced to the form of a thick syrup. The matter which re mains in the retort crystallizes as it cools. The crystals thus formed are urea.
Urea, which is prepared by this pro cess, is crystallized in the form of plates, crossing each other. It is viscid, resem bling thick honey, and of a yellowish white colour. It has a strong acrid taste, and a fetid alliaceotis smell. It deliques
ces in the air, and by attracting moisture is converted into a thick brown liquid. It is very soluble itt water, and also in alco hol. The solution in water concentrated is of a brown colour. This solution is gradually decomposed, air is emitted, which is partly composed of ammonia, and acetic acid is formed in the liquid. If the solution in water be boiled, and as the vaporation goes on fresh portions of wa ter be added, the urea is decomposed ; carbonate of ammonia is disengaged, while acetic acid is formed, and charcoal pre cipitated. The component parts of urea, therefore, are supposed to be Oxygen 19.5 Azote 325 Carbon 14 7 Hydrogen . . . • 13.3 100.0 - The caustic fixed alkalies readily dis solve urea, and disengage from it ammo nia; and the solution contains the benzo ic, acetous, and carbonic acids, united with the alkali employed. The urea al most entirely disappears from urine dur ing, certain diseases, and a very large quantity of saccharine matter is produced, which, when evaporated and clarified, re sembles Muscovado sugar.