Wohler's discovery showed that not only could organic chemicals be modified by chemistry, but that they could also be produced through chemistry as well. Stress and illness can predispose patients of any age to mild/partial enzyme defects, which lead to small increases in blood ammonia levels. It's been around for nearly half a century and was first used in the power generation industry to reduce oxides of nitrogen from coal-fired power plants. It is also essential for making feedstock, glue, fertilizer, commercial products, and in resin production. However, urine is produced in the kidneys through the urination. Also, urea has the ability to weakly bond to many large organic compounds, surrounding them in an inert 'shell' and so inhibiting intermolecular hydrogen bonding. But the ammonia is toxic to cells, and so must be excreted from the body. Urea has quite an interesting history. It's pretty good, but they still use bone in their most expensive classicals. This is usually removed from the body via urine. Understanding this increasingly visible emissions control system is becoming more and more critical as US truck manufacturers begin to offer more diesel models in traditionally gasoline-dominant segments. As with any source of nitrogen, urea itself can damage plants: nitrogen impairs or completely impedes seed germination, and too much nitrogen can give crops a “burn.” When OTC is deficient, hyperammonemia (excess ammonia in the blood) can occur. When he added silver cyanate to ammonium chloride solution he obtained a white crystalline This is then safely taken via the blood to be filtered through the kidneys. It's that oxides of nitrogen thing that you need to keep in mind because its those compounds -- nitrogen monoxide and nitrogen dioxide -- that are the big problems with diesel combustion and they're what gave Volkswagen and their lot so much trouble. Nobody likes paying more money for something inconvenient. This theory maintained that living organisms, like plants and animals, were made of different materials to inanimate objects like rocks. Where DEF really becomes critical is in big diesel engines. Symptoms of urea cycle disorders include: Treatment for uric acid cycle defects involves the following: Most mammals use uricase enzymes to metabolize the uric acid into a soluble compound. The urea is produced from ammonia and carbon dioxide. A 2.5-gallon pack of BlueDEF (as opposed to the stuff your dealer might sell) will set you back well under $20. These vehicles do millions of miles over their lifespans, and their massive diesel engines go through a lot of fuel in that time. That takes care of the "rolling coal" aspect of old diesel engines that made them relatively unpopular in the US in the 1960s, 70s and 80s. Well, not everyone is convinced that SCR and DEF are good things. First of all, selective catalyst reduction isn't new technology despite only having been mandated by the EPA in the last decade or so. Urea is the end product of a series of biochemical reactions, and the urea production occurs at liver, then is transported to kidney, at last, excreted as urine. In adults side effects are generally few. This behaviour prevents the large molecules sticking together, and so can be used to separate mixtures, in, for example, the production of aviation fuel and lubricating oils. This discovery dealt a severe blow to a widespread belief at the time called "vitalism". The days of brand new production vehicles spewing massive black clouds of diesel exhaust fumes are over, largely thanks to the introduction of diesel exhaust fluid and selective catalytic reduction. Urea can react with formaldehyde to make the urea-formaldehyde resins, which are highly important in moulded plastics. Besides the risks of kidney stones, uric acid is filtered through the glomeruli, but most of it is reabsorbed. The belief was that living organisms possessed an unknown 'vital force' that allowed them to fabricate organic chemicals, and since inanimate objects did not possess this force, they could neither create, nor be transformed into the chemicals of life. That's an important thing to remember. This leads to the build-up of highly toxic ammonia in the system. In effect, he had shown that we are made of the same materials as the rest of Nature, and are therefore a part of the world around us.