Urea
A colorless crystalline compound, formula CH4N2O, melting point 132.7°C (270.9°F). Urea is also known as carbamide and carbonyl diamide, and has numerous trade names as well. It is highly soluble in water and is odorless in its purest state, although most samples of even high purity have an ammonia odor. The diamide of carbonic acid, urea has the structure below.

Urea occurs in nature as the major nitrogen-containing end product of protein metabolism by mammals, which excrete urea in the urine. The adult human body discharges almost 50 g (1.8 oz) of urea daily. Urea was first isolated in 1773 by G. F. Rouelle. By preparing urea from potassium cyanate (KCNO) and ammonium sulfate (NH4SO4) in 1828, F. Wöhler achieved a milestone, the first synthesis of an organic molecule from inorganic starting materials, and thus heralded the modern science of organic chemistry. See also Protein metabolism.
Because of its high nitrogen content (46.65% by weight), urea is a popular fertilizer. About three-fourths of the urea produced commercially is used for this purpose. After application to soil, usually as a solution in water, urea gradually undergoes hydrolysis to ammonia (or ammonium ion) and carbonate (or carbon dioxide). Another major use of urea is as an ingredient for the production of urea-formaldehyde resins, extremely effective adhesives used for laminating plywood and in manufacturing particle board, and the basis for such plastics as malamine. See also Fertilizer.
Other uses of urea include its utilization in medicine as a diuretic. In the past, it was used to reduce intracranial and intraocular pressure, and as a topical antiseptic. It is still used for these purposes, to some extent, in veterinary medicine and animal husbandry, where it also finds application as a protein feed supplement for cattle and sheep. Urea has been used to brown baked goods such as pretzels. It is a stabilizer for nitrocellulose explosives because of its ability to neutralize the nitric acid that is formed from, and accelerates, the decomposition of the nitrocellulose. Urea was once used for flame proofing fabrics. Mixed with , urea is applied to limestone monuments to slow erosion by acid rain and acidic pollutants.
The end-product of nitrogen metabolism, excreted in the urine. Chemically it is CO (NH2)2. Synthesized in the liver from ammonia and the amino acid aspartic acid; the major nitrogenous compound in urine, and the major component of the non-protein nitrogen in blood plasma.

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