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The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.
The soil's pH also has a strong effect on the amount of volatilization. Specifically, highly alkaline soils (pH~8.2 or higher) have proven to increase urea hydrolysis. One study has shown complete hydrolysis of urea within two days of application on such soils. In acidic soils (pH 5.2) the urea took twice as long to hydrolyze. [7]
Example conversion factors, known as N factors, for foods range from 6.38 for dairy and 6.25 for meat, eggs, maize (corn) and sorghum to 5.83 for most grains; 5.95 for rice, 5.70 for wheat flour, and 5.46 for peanuts. [7] In practice, 6.25 is used for almost all food and feed regardless of applicability.
The k cat /K m of urease in the processing of urea is 10 14 times greater than the rate of the uncatalyzed elimination reaction of urea. [5] There are many reasons for this observation in nature. The proximity of urea to active groups in the active site along with the correct orientation of urea allow hydrolysis to occur rapidly.
The Dumas technique has been automated and instrumentalized, so that it is capable of rapidly measuring the crude protein concentration of food samples. This automatic Dumas technique has replaced the Kjeldahl method as the standard method of analysis for nutritional labelling of protein content of foods (except in high fat content foods where ...
Urea is usually spread at rates of between 40 and 300 kg/ha (35 to 270 lbs/acre) but rates vary. Smaller applications incur lower losses due to leaching. During summer, urea is often spread just before or during rain to minimize losses from volatilization (a process wherein nitrogen is lost to the atmosphere as ammonia gas).
The first symptoms of kidney failure are silent. Failing kidneys can’t remove extra fluid from the body, nor can they filter molecules like urea, which can be toxic in high dosages, from the blood.
Blood urea nitrogen (BUN) is a medical test that measures the amount of urea nitrogen found in blood. The liver produces urea in the urea cycle as a waste product of the digestion of protein . Normal human adult blood should contain 7 to 18 mg/dL (0.388 to 1 mmol/L) of urea nitrogen. [ 1 ]