Urea
The urea or carbamide (DCI) is a Composé organics of Chemical formula C O NR 2 H 4.
Its natural synthesis by the animals brings into play 3 amino-acid: Arginine, Citrulline and Ornithin during the Cycle of the urea in the liver.
The natural urea, discovered in 1773 by Hilaire Round slice, is formed in the Foie at the time of the Cycle of the urea starting from the Ammoniaque coming from degradation from the Amino-acid . It is eliminated by the Urine. Its Synthèse in 1828 by Friedrich Woehler caused a revolution by showing that it is possible to synthesize an organic compound, apart from a living organism. This experiment marks the beginning of the Organic chemistry and the end of the theory of the vital Force. Woehler synthesized urea after having controlled the synthesis of the Cyanic acid . By treating it by ammonia, one obtains ammonium cyanate which urea isomérise.
The urea is used in industrial Chimie for the plastic synthesis of some S, the resins urea-formol (urea formaldehyde). The most important current use is the manufacture of nitrogenized Engrais.
The urea is used also more and more on the thermal diesel engine vehicles like additive with the exhaust (drunk, heavy trucks, cars,…) in order to get rid of nitrogen oxides (Nox). The urea in liquid form is directly pulverized in the conduit of exhaust. The principal product resulting from the reaction is ammonia (NH3). This technology imposes the use of a specific catalyst whose role is to transform NH3. The objective of this technology is to make it possible the vehicles to pass the antipollution standards. Recall: Standards EURO4 (standard 2006) and EURO5 (standard 2009).
Proportioning of blood urea
The urea is filtered by the renal Glomérule and is reabsorbed partially (approximately 40%) by the renal tubule. The intensity of its reabsorption depends largely on the level of the urinary concentration (stronger reabsorption when the concentration is higher).A Impaired renal function thus increases appreciably its concentration in blood ( uraemia ). However its proportioning is less reliable than that of the Créatinine to evaluate the renal function because the variation of its rate also depends on other factors: it increases in particular at the time of the modes rich in proteins and in some other situations
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