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This is an old revision of this page, as edited by 61.68.4.208 (talk) at 22:29, 17 December 2017 (→Previous discussions). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

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)[reply]

Don't have my Merck Index handy at the moment for a citation, but it is from memory on the order of 10 moles/L in water, but 8M (moles/L) is readily soluble in aqueous solutions, and our lab has made almost literally hundreds of the 8M Urea solutions in water.Biotechscientist (talk) 02:09, 8 July 2011 (UTC)[reply]

The solubility of urea at 20°C is 107.9 g/100ml of water (Source: "Tablice chemiczne", Adamantan 2004).

According to the OECD the solubility of urea is 1080g/L and it's dead wrong. The value is more like 9 M. Reference Wang et. al. 2009 "Aqueous Solubility Prediction Based on Weighted Atom Type Counts and Solvent Accessible Surface Areas". They did experimental validation and it fits with what I have on my bench right now. Structurebiologist (talk) 14:17, 6 August 2013 (UTC)[reply]

Contradiction (resolved)

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.
Since removed. Adrian J. Hunter(talk•contribs) 09:14, 24 May 2008 (UTC)[reply]

Being born with mild ichtiosis the "snake skin" disease? I can attest that the only topical cream that works for me is 25% Urea. It accually allows the scales to slough off like normal skin does. When you have ichtiosis you apparently don't shed dead skin easily and don't sweat. Also you can become overheated very easily. It is strange that I actually get overheated & almost sweat when wearing the urea lotion. I wonder if this has anything to do with the prior article on whether or not urea is actually excreted in sweat considering that I don't sweat. Do you think it is a difficiency of urea in my body? —Preceding unsigned comment added by 75.130.102.58 (talk) 01:50, 16 February 2009 (UTC)[reply]

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!

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

Probably not. Heat urea in a flame and ammonia is released. Not exactly the most pleasant of flavors. Just another PC bit of pseudo science, referenced from a newspaper. The best one I've seen is that cig makers add Polonium for flavor. Polonium is present in nearly all US agricultural products, in tiny amounts. Po is in the decay chain of Radium found in North American rock fertilizer.61.68.4.208 (talk) 22:28, 17 December 2017 (UTC)[reply]

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)[reply]

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

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]
Please check under "Physiology" section. It has been updated. Urea is vastly important. Yay to a high school student for pointing that out. A0900 06:50, 30 October 2007 (UTC)[reply]

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.

--

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]

--

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)[reply]

No one can change the nitrogen content in Urea, if they did, it wouldn't be Urea. The nitrogen content gives a relative purity of the Urea you are purchasing, because it is produced from ammonia (NH3, and thus the nitrogen) and CO2 (current cheapest commercial production process). See Ullman's Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH & Co. KGaA, a whole chapter on Urea.Biotechscientist (talk) 23:44, 14 July 2011 (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 --Cowbert 23:37, 25 April 2006 (UTC)[reply]

See discussion below on pKa and pKb's.Biotechscientist (talk) 23:46, 14 July 2011 (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?

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)[reply]

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)[reply]

NEeds section - Urea Structure

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

There is a serious error in the diagram of the urea molecule at the top of the article. It doesn't show the carbon atom.Nigelrg (talk) 16:55, 29 July 2015 (UTC)[reply]

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) A0900 06:46, 30 October 2007 (UTC)[reply]

dialysis/comment on high urea load being dangerous

I believe there has been research that has shown that a high urea load is actually not in and of itself dangerous. More to the point, I think there's been a paper that's shown that urea just SIGNALS that something else is wonky and needs to be removed from the blood (mostly likely ammonia). I believe the experiment done was actually dumping a whole bunch of urea into pts' blood to see what would happen and answer was essentially nada. Or maybe this is just one of those, "I heard it in rounds and it isn't actually true" things. There are a TON of uncited "facts" on this page. Anyone dealing with this, would you please check on this particular "fact" that someone's listed? IF you find otherwise (i.e., that urea actually is a problem) then perhaps a mention of dialysis would be warrented? A0900 06:46, 30 October 2007 (UTC)[reply]

Medical Uses

There's no reference whatsoever to the Urine Therapy page, which is sad. Regardless of its effectiveness or medicinal reputation, it should be mentioned. Furthermore, drugs that are derived from urine (Premarin for example) are not mentioned either in this wiki. Why not? 24.247.170.144 (talk) 16:36, 29 July 2008 (UTC)[reply]

There is now. I added urine therapy as well as its use in abortion.
http://en.wikipedia.org/w/index.php?title=Urea&diff=237470477&oldid=234955931 BillyTFried (talk) 10:18, 10 September 2008 (UTC)[reply]

Why does everyone call it an organic compound?

The usual definition of organic chemistry requires carbon-hydrogen bonds. Urea does not have even one C-H bond (all of its bonds are heavily polar, in fact), so why does everyone seem to call it an organic compound? I would argue that it isn't. At the very least, we should mention in the article that its organic-ness is somewhat debatable, though I am not sure how to word such a statement. Stonemason89 (talk) 01:47, 8 September 2008 (UTC)[reply]

See Organic compound for a discussion of the definitions of organic and inorganic compounds. There is no unique, universally-accepted definition of organic, but by convention, urea is considered organic.
Ben (talk) 13:58, 8 September 2008 (UTC)[reply]

Traditionally Inorganic Chemistry has been used to describe metal compounds, these compounds include the bridge in the periodic table (e.g. Si is a metal). I understand the definition of the CH bonds and it is 100% accurate, but more often than not, if there is carbon and no metals present it is organic. If there is carbon and metals, it is organometallic. So I am with Benjah on the organic, because nitrogen is not a metal.Biotechscientist (talk) 00:05, 15 July 2011 (UTC)[reply]

pKa and pKb values for urea

The provided pKa and pKb values are not possible - in a water solution pKa + pKb is 14. Presently, the provided values are pKb = 13.8 and pKa = 26.9, which is logically impossible. Unfortunately I don't have any better values to add. Anyone? Annelie Skoog (talk) 19:50, 1 December 2008 (UTC)[reply]

I changed the pKa value to 0.18, since the pKb value seems reasonable. With these values, urea will be an uncharged compound under all physiological conditions. An additional comment: since urea theoretically should/could be diprotonic, it should be possible to define pKb 1 and 2, as well as pKa 1 and 2.

Annelie Skoog (talk) 20:20, 1 December 2008 (UTC)[reply]

I can explain those values: 0,2 is the pKa of protonated urea in water, 26,9 is the pKa of urea in DMSO. Two very different things... --FK1954 (talk) 19:19, 2 March 2009 (UTC)[reply]

Ok, "in a water solution pKa + pKb is 14", this is correct, but remember this is a relative logarithmic scale centered at pH 7 for the first proton to go off of water, and one based on an ideal solution in thermodyanamics. pKa's can exist below 0 and above 14, what this means is in the case of pKa's below 0, there are very few hydroxyl's ions present in solution (to a certain degree that is estimated by the logarithmic pH scale (e.g. the log of negative number is not zero, and you are quantifying the number of protons with the log scale). To measure the pKa's of these in solution, you have to more often than not use organic solvents, hydrochloric acid has a pKa of like -3, what this means is at pH -3, half of the molecules are charged, and the other half are protonated (definition of pKa). If you are interested in learning more about this, look up superacids. The oxygen on Urea will become protonated in accordance with its pKa of 0.2 at pH's comparable on the pH logarithmic scale (e.g. the lower you get in pH the more the protons stick to the oxygens). On the other end of the scale, many protons require extreme basic conditions to be removed, as is the case with the pKa of 26.9 (the amine (e.g. NH2) protons on Urea). In this case there are very few protons free in solution on the same logarithmic pH scale that would allow the NH2 to become NH-. Hope this helps, I find that many entry level people still struggle with this even after a few college chemistry courses. Acid-Base equilibria if you can conquer it (and have good teachers) will help explain many erroneous things that occur day to day in laboratories.Biotechscientist (talk) 02:42, 8 July 2011 (UTC)[reply]

FK1954 is correct: The pKa of 0.1-0.2 is for the conjugate acid of urea H(O=C(NH2)2)+ (likely protonated on the oxygen, not one of the nitrogens, to maximize resonance stability). This value corresponds to the pKb of urea itself. Recall that pkA + pkB = 14 is true for a conjugate base/conjugate acid pair, such as A-/HA or A/HA+. So 0.2 (for HA+) + 13.8 (for A) = 14. Reengler (talk) 14:49, 26 April 2016 (UTC)[reply]

IUPAC name

I think that IUPAC name is wrong. It will be better if you could change it from aminomethanamide to diaminomethanal. --Qweeer (talk) 07:10, 14 March 2009 (UTC)[reply]

Why do you think this? Do you have a reference?
Ben (talk) 13:35, 14 March 2009 (UTC)[reply]

I just checked. The Preferred IUPAC name is the retained name urea, while the systematic name is carbonic diamide. See Rule C-971 of the 1979 recommendations and Chapter 6, Sect 66, September, 2004 P-66.1.5.1.1.1 of Preferred names in the nomenclature of organic compounds.

Ben (talk) 14:20, 14 March 2009 (UTC)[reply]

We can think of urea as inorganic or organic compound. It is hard to decide where is the bound between organic and inorganic chemistry, because this two parts of chemistry have originated from historical causes and they have different nomenclature. Urea can be derivate from carbonic acid or from methan. We can create urea from organic compounds but too from inorganic compounds. And the inorganic system name is carbonyl diamide and the organic system name is diaminomethanal. It is like compound with formula CF4. It´s carbon tetrafluoride or tetrafluoromethane. --Qweeer (talk) 17:25, 14 March 2009 (UTC)[reply]
Hmmm. Previously the article read "Diaminomethanal (as organic compound), Carbonyl diamide (as inorganic compound)"; a newly-registered contributor has just changed the organic name to "Diaminomethanone ([1]). I wouldn't have thought a chemical with one carbon should take the -one suffix, though that name is supported by this website, which may or may not be reliable. But really, although I understand what Qweeer says above, I'd have thought the P-66.1.5.1.1.1 link provided by Ben above should have been the final word on this issue, and the article should state "Urea (preferred name), carbonic diamide (systematic name)" per that source. Adrian J. Hunter(talk•contribs) 03:47, 4 June 2010 (UTC)[reply]
The IUPAC name for urea is, erm, urea! The current recommendation which sets this out is R-9.1, table 31(a). The problem with P-66.1.etc (as a reference) is that that set of recommendations has been fully approved yet, although I doubt it will change on this particular point.
Carbonic diamide is also a perfectly acceptible IUPAC name, but is not the one IUPAC recommends that people use. Diaminomethanal, diaminomethanone or even 1,3-diazapropan-2-one are all names which will get you to the correct structure, although they have the distinct disadvatage of implying that the compound is an aldehyde or a ketone instead of it being an amide. I can't repeat it often enough that IUPAC nomenclature does not necessarily generate a unique name for a given structure: it is designed to give a unique structure for a given name. Physchim62 (talk) 06:14, 4 June 2010 (UTC)[reply]

I changed it to Urea, as per Physchim62 above. End of discussion! Chris (talk) 09:13, 4 June 2010 (UTC)[reply]

Urea Nitrate?

70.171.235.197 (talk) 04:31, 1 July 2009 (UTC)Urea Nitrate should not be listed as a powerful, high explosive. Its power and velocity only resemble ammonium nitrate. 70.171.235.197 (talk) 04:31, 1 July 2009 (UTC)[reply]

Solubilities!!!

In the ammonia page, this same problem appeared a few weeks ago, it is here, and I see that it has occurred before (top discussion topic, 2007), was corrected, and seems to have re-appeared. The solubilities given must be off by an order of magnitude. Is there a bot that is doing this? Perhaps the numbers are referenced to a data table, but the units are not? Does anyone have information on this? Gaedheal (talk) 00:09, 25 February 2010 (UTC)[reply]

I believe the current figures are correct. The article currently gives figures such as 108 g/100 mL (20 °C), and has done so for a long time. The problem with earlier versions was that the figures were ten-fold higher, such as 1080 g/100 ml (20 °C). The lower figures are consistent with doi:10.1021/je60054a020 (requires subscription), which gives 109 g/100 mL for 21 °C, and measurements at other temperatures consistent with the Wikipedia article. That current figures also match my own personal experience: although urea takes forever to dissolve in water, it is nevertheless highly soluble, with an amount of urea dissolving in a similar amount of water at room temperature. Adrian J. Hunter(talk•contribs) 03:00, 25 February 2010 (UTC)[reply]

The figures currently listed on the page are more accurate (51g/100 mL~8.6M). 108 g is like 17.8M, and I have seen in three separate instances 10M Urea precipitating out of solution at 2-8°C. Our lab has been working with high concentration Urea solutions (4-8M Urea) for about a year, and we are at sea level to remove any atmospheric pressure issues. Our associates have made literally hundreds of these solutionsBiotechscientist (talk) 23:58, 14 July 2011 (UTC)[reply]

Contradictory assertions

Under "Uses": "Urea is also used in many multi-component solid fertilizer formulations."

and then, a few sentences later:

"Urea is not compatible with other fertilizers."

They can't both be right, can they ?Eregli bob (talk) 17:39, 12 May 2010 (UTC)[reply]

Melting Point of Urea

The mp of Urea is listed as 132.7–135 °C. Having 4 significant figures in the first term and not the second doesn't make any sense. It should either read 132.7-135.0 or 133-135. I'm going to change it to the latter. —Preceding unsigned comment added by Robertblankenship (talk • contribs) 03:35, 20 September 2010 (UTC)[reply]

Illegal intentions??

If my son is looking up urea on the internet do I need to be concerned that he is doing something illegal . . . like making meth? — Preceding unsigned comment added by 24.112.120.186 (talk) 03:00, 30 May 2011 (UTC)[reply]

I very much doubt it. Urea is a common biological substance and the most basic of starting materials; far more detailed research would be necessary to undertake such a complicated organic synthesis, and most likely your son was merely curious about the content of his urine. Furthermore, I am concerned that you suspect a family member of illegal activity due solely to their accessing this public encyclopaedia; you might consider scaling back the paranoia. Magic9mushroom (talk) 12:41, 17 July 2014 (UTC)[reply]

Out of Date Citation

Citation number 1 was for a search. However, this search has presumably expired long ago, and so you cannot access the information any more. Someone should remove it, and I think that whoever put it there should try to find where he got the information from, and find a better citation. 120.151.249.12 (talk) 21:03, 19 April 2012 (UTC)[reply]

spontaneous hydrolysis?

I removed the side remark from the introduction that urea produces ammonia in the presence of water or water vapor, as I believe this reaction does not occur spontaneously to a significant degree at room temperature, without a catalyst such as the enzyme urease produced by many soil microorganisms. It is for this reason that urease inhibitors are sometimes added to urea fertilizer. See article on ammonia volatilization from urea. I think discussions of conditions under which urea undergoes hydrolysis, and ways of catalyzing or inhibiting it, might be appropriate elsewhere in the article, but are too specialized for the introduction. CharlesHBennett (talk) 14:23, 18 April 2013 (UTC)[reply]

The article makes the statement that urea breaks down in water to form ammonia, and this is why old urine smells worse. I believe that this is due to the action of bacteria. I can't find a single source saying if or how fast urea breaks down in plain water. The merck says it breaks down when heated in water but gives no more information.50.133.241.236 (talk) 22:16, 18 August 2013 (UTC)[reply]

Ammonium cyanate as a redirect?

Given the Wohler reaction, ammonium cyanate should probably redirect to this page, but I'm not savvy enough to make a redirect. Could someone help out? Magic9mushroom (talk) 12:41, 17 July 2014 (UTC)[reply]

Bcwilmot (talk) 02:58, 14 December 2015 (UTC)[reply]

I wholly disagree. Not being a chemistry expert, urea has a formula of CO(NH2)2 or (NH2)2CO (depending on source) with a different physical structure from ammonium cyanate (NH4OCN). Yes, they have same atom count and elements used, but are isomers. See https://en.wikibooks.org/wiki/Organic_Chemistry/Foundational_concepts_of_organic_chemistry/History_of_organic_chemistry

Per Note 1) the sentence "Ammonium cyanate is urea." is false since ammonium cyanate (NH4OCN), is an inorganic salt, and urea ((NH2)2CO), is a biological compound. Why have a note attached saying the sentence is false? Why not just explain ammonium cyanate and its relationship to urea?

I have never seen a Wikipedia article have a (sub-)Note stating a sentence is not correct. Seems like a senior editor missed this.

Is Wikipedia simply for advanced scientists or for general readers trying to comprehend science?

Assessment comment

The comment(s) below were originally left at Talk:Urea/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Comment(s)Press [show] to view →
Hmm Urea is important molecule in body, yet article is lacking in many details. Phgao 16:00, 15 August 2007 (UTC)[reply]

I agree Urea is of top importance. It should also be noted that this article simply jumps into the the kidney's physiological functions in a very confusing manner. The article starts out really well however. Most people will not understand the way the section on human beings physiology is written. Three sentences in it finally says the word "renal" which means nothing to many people. Also it is written like something from a source not cited. Red flag. —Preceding unsigned comment added by Carnyland (talk • contribs) 06:58, 22 April 2009 (UTC)[reply]

I think that the diagram of the urea molecule shown on the upper right of the article is in error: the left branch should be -NH2 instead of -N2H. I think -N2H is impossible anyway. Isn't this simply an error in the diagram? -Michaelmartens — Preceding unsigned comment added by Michaelmartens (talk • contribs) 20:34, 10 February 2011 (UTC)[reply]

Last edited at 20:35, 10 February 2011 (UTC). Substituted at 09:44, 30 April 2016 (UTC)

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