Talk:Urea

Solubility of Urea

The article provides some specific information about the solubility of urea without giving a source. The values were out by at least a factor of 10 (probably g/L rather than g/100mL), which I have corrected by knocking off the last zero, but I don't know where the numbers come from in the first place and if they are accurate. Does anyone else know? dmcg026 10:01, 15 August 2007 (UTC)

Previous discussions

please add information on urine urea nitrogen (a medical lab result based on protein catobilic rate). when someone types in UUN, a link should appear to this or another urea page. when someone types in urine urea nitrogen, a redirect to somewhere should appear. maybe urine urea nitrogen should be its own article or stub.

Urea certainly works well on dry, cracked skin caused by severe athletes foot. I have been using a balm containing 25% urea for several days now, and there is a very noticable difference in my condition. What used to be hard, callous-like skin that was prone to cracking has now become soft, pliable, pink, and healthy looking! Masha Allaah!

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.

I was going to comment on the same thing. I can't find any trace of Dr M Falk of the RC Institute. The user who added it was an anonymous user who only ever edited two articles. I question the accuracy of this information.

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

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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).

Fixed the pKa - this value is from Philosophical Transactions: Physical Sciences and Engineering, Vol. 345, No. 1674, The Chemistry of Biological Molecular Recognition (Oct. 15, 1993), pp. 57-66 Stijndon 11:13, 24 October 2007 (UTC)

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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.

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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

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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)

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)

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)

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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)

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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.

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

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)

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When i asked about buying urea from a company, they told me that the nitrogen it contained is over 46% (it might be the purity?!). I'm just wondering, how do they change the nitrogen content in urea? Or i've misunderstood something? tks~

Pure urea necessarily has only one nitrogen content (law of definite proportions). --Vuo 14:46, 24 October 2007 (UTC)

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)

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)

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?

Importance of urea

Urea is the first organic compound synthetically made from an inorganic salt. It has historical significance. --Kupirijo 05:15, 1 December 2006 (UTC)

Effect on environment

I don't have enough knowledge of this area to write an authoritative overview, but I feel it should be mentioned, especially as urea is a widely used fertilizer and the highest in nitrogen. Something on eutrophication of rivers, lakes and seas would be appropriate. Richard001 21:10, 30 January 2007 (UTC)

NEeds section - Urea Structure

On H-bonds in Urea, thats why high solb.

Physiology section--editing

Hi. I just did a slop-job of an edit on the physiology section. I just went there to look up a quick tidbit and it was just...strange. So I did what I could. I couldn't find good solid references on the web, so I'm afraid I didn't cite any, but below are a couple that are good starts (uncitable, but good explanations for the uninitiated). Also, I'm afraid my language is a bit dense. However, it's got to be better than what was there before, and at least I've got mad internal links. Can't spend time on it, I'm afraid. Here's my encouraging, "Woo-hoo!" to whoever will spend the time on it that it deserves:)

Links that might help whoever wants to work on it: http://www.acbrown.com/renal/OutLoop.htm AND http://www2.kumc.edu/ki/physiology/course/seven/7_4.htm (btw, I haven't really looked through them so I'm not completely endorsing them)