Talk:Urea

There is a contradiction between the entries on Sweating and Urea. I hope this is the right place to post this. This is my first comment.

The article on Sweating states that "Sweating (also called perspiration or sometimes transpiration) is the production and evaporation of a watery fluid, consisting mainly of sodium chloride (commonly known as salt) and urea in solution, that is secreted by the sweat glands in the skin of mammals."

The article on Urea states: "Many researchers used to believe that a small amount of urea was excreted (along with sodium chloride and water) in human sweat. However that was proved wrong when Dr. M. Falk determined at RC Institute that only sodium chloride and water are excreted from sweat.”

I don't know for sure which is correct but sweat either contains urea or it does not. Whoever wrote the paragraph at the article on Urea seems certain that sweat does not contain urea while the article on Sweating states that it does.

I have left this same comment at both articles on Urea and Sweating.

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Is it really true that urea is added to cigarettes for flavor?

I believe the pKa value of 0.18 for urea is incorrect; this is the value for the acylium ion of urea (a much more acidic species). The lower the pKa the more acidic. Since the pH of 10% water solution of urea is 7.2, I don't think urea is acidic(Merck Index, 12th edition).

How did the early chemists isolate urea from urine or other biological samples?

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Hang on, At least sharks produce urea and they are aquatic.

Someone changed the 'Lab use' section to say that it is used in concentrations up to 10M (rather than 6M, as it said before). I don't think that you can actually make a solution of urea that concentrated, at least under mild conditions. I'll leave it as I don't know for sure, but this may be inaccurate. ike9898 14:17, Feb 2, 2005 (UTC)

Sigma-Aldrich is one of the largest chemical supply companies for labs, I have just looked in their catalog and they have 8M Urea avalible. http://www.sigmaaldrich.com/Brands/Sigma/Sigma_General_Catalog.html Onco p53 19:48, 2 Feb 2005 (UTC)

According to a MSDS I found, solubility at 74 F is 119g/100g water. This works out to 10.5M assuming densities of solution is additive and sp gr's water 1.00; urea 1.34. This is a very conservative assumption, so if data is right 10M should not be a problem! (A 10% soln. has sp gr of 1.14 or 1.9M (6th Merck Indx); using above assumption sp gr would be 1.03 or 1.7M (thus underestimating Molarity)) DEN 6/10/05

I would like to comment on this page from the perspective of a high school student taking a biology course. This article on urea is very informative about the composition and alternative uses of urea, but I frankly am totally lost as to what urea actually does in its natural function. Perhaps some description of its function, or at least something clearer (in case I simply cannot discern its function)would add to the usefulness of this article.

It's a waste product from amino acid metabolism. It has no intrinsic function. JFW | T@lk 20:44, 2 November 2005 (UTC)[reply]

Wait, if it has no nutritional function at all, why does the yeast nutrient I use in homebrewing contain it? Does yeast have some use for it? teucer 01:22, 19 November 2005 (UTC)[reply]

This paper proposes that urea somehow protects yeast cells from being poisoned by the ethanol they are producing by sequestering inorganic pyrophosphatase (the enzyme that yeast use for inaerobic respiration to make ATP) away from the ethanol. The interesting thing is that urea itself is a protein denaturant (as is ethanol).--Cowbert 23:29, 25 April 2006 (UTC)[reply]

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According to this website, urea is used by the skin along with epidermal lipids and proteins to keep itself moisturised and apparently "represents 7% of the natural moisturising factor in the outer layer" Tizer128 02:11, 12 May 2006 (UTC)[reply]

In the discovery section, I see the following:

"Although Rouelle was attempting to prepare ammonium cyanate, he inadvertently disproved the theory that the chemicals of living organisms are fundamentally different from inanimate matter by forming Urea, thus starting the discipline of organic chemistry."

Is this about Rouelle or Woehler? I am vaguely familiar with Woehler's story, and this seems like a small typo, but I'd like someone more authorative to make the call.

Sweat contains how much urea normally, please ? --213.7.155.164 11:46, 12 January 2006 (UTC)[reply]

nitrogenous compound in urea

I may be wrong, but I was comparing the definition for urea on wikipedia with the definition in my copy of Merriam-Webster's Medical Desk Dictionary and I found that the chemical formula in my dictionary did not agree with the chemical formula in the wikipedia definition. My dictionary says that the chemical formula of the nitrogenous compound in urea is: CH4N2O

I'm curious Which is correct.

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CH4N2O and CON2H4 are chemical formulae, i.e. they give the number of atoms of each element in the molecule (neither is wrong), whereas (NH2)2CO gives the structural formula, which tells you how the atoms are arranged, i.e. a carbonate group attached to 2 amine groups. Tizer128 01:30, 12 May 2006 (UTC)[reply]

Acid/Base Equilibria

Can someone provide some better Ka and Kb data? Based on Google, I have found people (1 2) saying the Kb is $1.5x10^{-14}$ --Cowbert 23:37, 25 April 2006 (UTC)[reply]

Physiological Diagnosis section should be removed

I have just edited the Physiological Diagnosis subsection in the Medical Use section.... But I actually think that it should all be moved/incorporated into the blood urea nitrogen entry. It seems to me that the Urea entry should mostly focus on the chemical urea and not on the medical/physiological issues.

I would favor having only the following line under the Physiological Diagnosis subheading:

See blood urea nitrogen ("BUN") for a commonly performed urea test, and marker of renal function. DanLevy 19:46, 14 May 2006 (UTC)[reply]

Prills versus pills

I do not know if urea is also produced as pills (or pellets), but the vast majority of commercially produced urea is produced as prills. Prills are prepared by letting small droplets of molten urea fall in high prilltowers. During the fall the droplets solidify, giving round particles of generally 1.4 - 2.0 mm size.

urea in soil

I was looking for scientific explanation about how and what for urea is used by microorgnisms in soil.

yeah...me too..can somobody help me with our investigatory project? it's isolation of urea from urine...but we really dont know how...=) do you have any idea?