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Author: Subject: Isolation of urea from urine!
chemoleo
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Isolation of urea from urine!

No, I am not kidding!

I have always been interested in the chemicals the body produces/excretes, and urea is one of them!
Of course, urea is mostly easily available, but not everywhere. So there are ways of obtaining it yourself, from a chemical synthesiser called your own body

Urea is of course an ancient, well studied chemical, in fact it was discovered over 230 years ago, and Friedrich Woehler determined that urea could also be synthesised from inorganic chemicals, i.e. by the reaction of potassium cyanate with ammonium sulfate (1828).

The original discovery of urea was by Hilaire Marin Rouelle in 1773, who obtained it by boiling urea dry and obtaining a white residue (which later proved to be identical with Woehlers reaction products - disproving the idea that the chemistry of the living is radically different from inanimate matter)

Unfortunately, simply boiling down urine doesnt quite satisfy anyone, as it still contains certain quantities of salt, creatine, ureic acid, proteins etc.

Per day, about 1.5 - 2 litres are excreted, consisting of 95% of water. The rest (in grams per day consists of)

# 25 g urea
# 1 g uric acid (metabolic endproduct of purines from DNA)
# 1.5 g creatinine (derived from creatine phosphate, the muscle booster)
# 10 g of salts, mainly NaCl
# 3 g of phosphates, citric acid, oxalic acid,
# milligrams of proteins, and urochromen, which is the compound giving rise to the yellow colour of urine.

Now, looking at this information, what could be the best way of isolating urea from it?

1. Collect urine for about a week, one should get about 10 litres. Needless to say, urine is STERILE to start off with. Preferably though, after each urine addition, the solution should be simply boiled to keep it sterile. Otherwise, just literally pee into a sterile pot with lid, and keep it at 4 deg C for the rest of the week. I dont think bacterial contamination should be a problem then (unless your have a medical condition, where bacteria are excreted through your urinary tracts)
2. AFter a week, boil down the urine, until a solid mass is obtained (from the above table, it should way about 300 grams. Do this outside, unless you want 10 litres of water condensing on your windows
3. That's when things become interesting. You want to get rid of salts (primarily), and phosphates. At this point there is no easy way to get rid of the creatinine, and the ureic acid. Proteins aren't much to worry about anyway, as conc. are very low.
So - I checked - urea is soluble in ethanol, at 50 g / l, @ 20 degC . Probably a lot more is soluble at higher temperatures. In water, it dissolves at >1500 g/litre, so very highly soluble. I'd try to dissolve the urine residue in an excess of cheap industrial ethanol (doesnt matter if it contains other things), which would mean, around 3 litres, if you heat the ethanol up a little (no open flames ok). All the inorganic stuff (salts etc) are barely soluble in ehtanol, so they should remain precipitated.
4. Filter off the remainder, and boil of the ethanolic solution of urea (with a small amount of creatinine potentially) down to a few hundred ml's, or even to dryness. If you distill, you can obviously recycle the ethanol, although it may prove to be a pain to recycle such large amounts, considering that ethanol is cheap anyhow.
5. Alternatively, once you boiled down the ethanolic solution of urea to a few hundred ml, you could add HCl (conc) or H2SO4, and precipitate urea as the respective salt (which is surely insoluble in ethanol). The salt can be turned back into urea with the appropriate amount of NaOH.

What do you think? Sure this is a very simple way of purifying urea, and of course if you had all the reagents, one could get extremely high purities.
At least, this way, one gets about 200 g of urea, straight from urine, with the only expense of 3 litres of industrial ethanol.

[Edited on 10-1-2010 by chemoleo]

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Polverone
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I'm pretty sure that the "established" method of isolating urea from urine is to boil down the urine to concentrate the solution, then add nitric acid. Urea nitrate is relatively insoluble and precipitates. I think Megalomania's chem lab had a more exact procedure for this. Then you can take that small amount of solid and treat it with NaOH and ethanol to get the urea back.

I like this method because it should sharply separate urea from not-urea, and may require less energy (less forced evaporation). Urea oxalate is also fairly insoluble and can be precipitated from an aqueous solution containing urea.

Edit: sodium oxalate is isn't very soluble either, so I suppose HNO3 is the way to go.

[Edited on 8-12-2004 by Polverone]

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I know this forum advocates mad science, but isn't collecting urine going a bit too far? Amateur chemistry is a hard enough hobby to justify already, without having jars of urine to explain.

Then again, there are worse things you can do with it...

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chemoleo
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To be honest, I don't think it goes too far at all.

Let me remind you that many diseases are diagnosed by analysing urine. Which means the person concerned has to fill a cup with it, and pass it on to the laboratory, who analyses it down to the last molecule. People are handling it every day and don't complain it goes to far. Oh, you may argue they do it because it's necessary, while purifying urea from urine isn't. Is that how you define 'going too far', however? Whether something is necessary or not?

By the way, in practical biochemistry classes, we analysed our very own urine for vitamin C content - which wasn't strictly necessary - and yet noone complained doing it.

Also, let me remind you that in biochemistry, urine is routinely used to purify certain enzymes. In fact, I worked with enzymes directly isolated from my own urine. So what? It's natural, and by no means sick, disgusting or dirty. Your blood is equally dirty (indeed your lymph fluids consist of less concentrated urinal fluids).
How is it different to isolate urea from urine, or glycogen from liver, cysteine from wool, or oxalic acid from rhubarb? The only difference that these are excretions - but it's still as natural or unnatural as anything else. What's the big deal?

Hmm - am I lacking perspective or something?
I thought that the idea/philosophy behind this, in essence, is no different to a lot of other chemical problems/purifications - if you ignore this totally unreasonable 'disgust' factor - totally unreasonable because urine is sterile, contains about 200 compounds, und doesnt even smell, unlike pancreatic enzymes / bile and such - which have been analysed to death just as well.
Again - where's the big deal? And what's this to do with the link ?(pee drinking - what the hell)

[Edited on 12-8-2004 by chemoleo]

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ziqquratu
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I'd just like to say, urea is NOT inherently sterile even in healthy people. First of all, it is not that unusual for a few bacteria to be present in the bladder (although these are generally transient - if they colonise, you get an infection).

Secondly, urine is typically contaminated as it leaves the body, as bacteria are relatively common in the urethra, certainly towards the end.

That's why when you give a urine sample for disease testing the doctor will ask for a "mid-stream" sample - you will pee about a third of the contents of your bladder, stop, stick the cup under there, fill the cup and then finish off. THe first third is designed to (hopefully) wash away any transient bacteria.

Diagnosis of urinary tract infections is actually a statistical thing - if you detect a single live bacterium in the blood, for example, it is immediately considered an infection. But because of the relatively common contamination of urine, you have to have more than a cecrtain threshold level present in the sample to be considered an infection.

Thought somone might like to know this... trust me, nobody needs to work with semi=fermented urine samples (it's FAR from pleasant!!)
chemoleo
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Of course, semi-fermented urine samples aren't pleasant. That's why I suggested boiling them.
But then, is the smell of ammonia pleasant? Surely not. Except, in the former case, ammonia is produced bacterially...

Anyway - the debate is not so much about the issue whether it's sterile or not (and I agree about your mid-stream sample), but simply whether this particular case is 'science that goes too far'.
And I just happened to disagree on that - if anything, I'd say, the making of highly toxic nerve gases is science that goes to far, at least for the amateur chemist!

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Geomancer
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Actually, I found the link somewhat interesting, although it failed to substantiate most of its positive claims. For example, I've always been taught that ingesting urine is counterproductive in preventing dehydration. They even intimate that "urine therapy" can be usefull in treating gout, a disease caused by excessive levels of uric acid!
S.C. Wack
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US5659080 from the E&W archives:
In a 100 ml beaker was placed a solution of 50 grams of 33% diluted nitric acid, and to this solution was added 14 grams of urea in small portions while stirring vigorously. For this period of time, since the temperature does not show any rise practically, this reaction can be carried out in room temperature and is not necessary to be kept cool. Immediately urea nitrate resulted as crystals. Having been allowed to stand for 10 minutes, the mixture was filtered to collect the crystals. This crystals were washed with a little amount of water to remove the solution well and were then dried in a desiccator under vacuum. The yield resulted in 23.8 grams of urea nitrate (97% yield), whose melting point was measured to be 162.degree. C.

Urea and uric acid extraction from urine was good enough for Wieland's revision of Gattermann. It was isolated using colorless 70% HNO3. All the other old refs use the conc. acid as well. And all use BaCO3, K2CO3, or KHCO3 to give the metal nitrate.

The oxalate was made with hot satd soln of oxalic acid and syrupy urine. Like the nitrate it is not very soluble in excess of the acid. The oxalate is decomposed with CaCO3 suspension. This has the advantage of forming insoluble Ca oxalate, and the aqueous solution is filtered and evaporated.

Decolorizing was done with charcoal or boiling H2O2.
chloric1
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Using nitric acid to separate urea is quite a waste of HNO3.
 Quote: Edit: sodium oxalate is isn't very soluble either, so I suppose HNO3 is the way to go.

Yes but potassium oxalate is soluble and oxalic acid is more readily available and cheap. The potassium oxalate is a usefull byproduct for other syntheses.

Did some looking around and it appears that most of the sources state that the urea oxalate would best be hydrolysized by calcium carbonate effecting the precipitation of calcium oxalate leaving the urea in solution. Urea is a really weak base so I see little difficulty here. Will try sometime but I am leaving the country for two months so experimental results will be delayed.

[Edited on 12/1/2008 by chloric1]

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Mr. Wizard
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Urine was used for many things in past times. Aged urine even had a name: lant.
Vogelzang
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Have you considered using the urine to make red phosphorus?

hissingnoise
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Whew! Boiling down large volumes of malodorous liquid---great way to "piss" off the neighbours. . .
And large volumes would surely be needed.

U235
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Increasing the yield:

BTW, you can increase the amount of urea excreted: by eating more protein for a few days. The daily need is quite constant except when you have wounds or infections, or while training of muscles---about one gram per kg body mass. Any more than this is made to urea (in the urea cycle) and excreted.

That doesn't mean *any amount more than 1g/kg is excreted as urea. Huge amounts are probably not even digested and pass with the stool (or is then rather eaten by intestinal bacteria).

I would also put in a slight caveat on too much protein over long time periods: it's a risk factor for getting struvit kidney stones.
hissingnoise
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I'm on a diet of greens---need some KNO3. . .
ScienceSquirrel
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Technical grade urea ca 98% is readily available as a fertiliser almost everywhere.
A couple of recrystallisations would result in very high purity material.
There are a few interesting derivatives that can be prepared eg the nitrate, oxalate etc and you can make acetamide, benzamide etc using it.
Isolating urea from urine might be interesting on a small scale but it would use large amounts of reagents that would cost more than the urea if scaled up.
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$12.95 17# 46-0-0 . the ancients used human urine to brush thier teeth and whiten them,yum yum.Of course the ammonia used to whiten the teeth removed the hard outer layer of dentine.One would think cat urine with its ammonia content would work well to promote severe dental decay. I believ ammonia(in a more palatable form) was used for this purpose until the 19th century until 'modern dentistyry discovered the damage inherent. Sorry so OT it is interesting no?Bye the bye vthe majority of users were royals or the rich deserving of what they got IMHO.LOL Fertlizer grade urea is often laden with foriegn materials trash etc easily removed with water solubility /filtering. which could easily make up the 2% of the fertilizers ive seen. [Edited on 1-9-2009 by grndpndr] Various Harmless Posts: 7 Registered: 1-10-2009 Member Is Offline Mood: No Mood  Quote: Originally posted by grndpndr$12.95 17# 46-0-0 . the ancients used human urine to brush thier teeth and whiten them,yum yum.Of course the ammonia used to whiten the teeth removed the hard outer layer of dentine. [Edited on 1-9-2009 by grndpndr]

What's your source of that information?

It is believed that in Pompeii they collected urine to use part of it as a bleach, I guess the ammonia.
Mr. Wizard
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I don't have a source either but it's common knowledge it was used to brush teeth and bleach hair. A quick Google found many references. I even read once where it can be used to wash cobra venom from your eyes. and to keep entrails moist in the event of an evisceration. It's not always sterile, but it is approximately normal saline and probably cleaner than any other liquid quickly at hand. It can even put out a campfire.

In times of war in the black powder era, it was zealously collected to make niter.
hissingnoise
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 Quote: Originally posted by Mr. Wizard and to keep entrails moist in the event of an evisceration.

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I was reading in Beilstein and came upon N,N-dichloro-urea, which has solubility of 4g per 100g H2O at 0º (Chattaway, Am. 41, 91). So I was thinking maybe it is possible to form it from a cold conc. clear urine solution, and thereby precipitate in a similar way as oxalate and nitrate, hoping no other troublesome compounds would form.

The compound is covered in Chem. News. 1908, 166, Chattaway (just go read it), and it certainly has its dangers but according to the latter it seems it can be handled at least for a short time and at lower temps and with the right precautions without too much risk. Dichlorourea is also a simple way to near quantitative hydrazine sulfate (Chattaway).

But I don't know how one would be able to reduce the N-substituted compound safely into the urea form without too much exertion. So I'm open to ideas on how to get to urea itself.
hissingnoise
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Can you buy fertiliser-grade urea in your area - if you can, it usually works out dirt cheap.

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Formatik: Do you have that paper as an electronic file? I cant find it online...
Formatik
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Here you go. It's attached below.

I know urea can be bought very cheaply, it gets harder to find nowadays. But I'm also interested in the chemistry.

Attachment: Chem. News, 1908, 166 Chattaway.pdf (107kB)

chemoleo
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Very interesting - although dichloro urea is precipitated from a saturated (about 8 M!!!) solution of urea through which chlorine gas is fed.
There's no telling how well this would work in the presence of all the other things contained in urine....

Far more exciting I thought is the almost quantitative production of hydrazine from it - anyone who's ever boiled NaOCl with urea knows the terrible yields of hydrazine that are obtained - and here's a route that requires urea, chlorine gas, ammonia, and sulfuric acid only! Perhaps that warrants a post in the hydrazine thread!

[Edited on 9-1-2010 by chemoleo]

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Formatik
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At least monochlorourea has come up in the hydrazine thread. It was discussed on pg. 5 of that thread. Garage chemist on the following page also described his results with the method.

The question is indeed how extractable or even safe it would be to attempt to form the compound by the urine route. It is another precipitateable urea form.

From Wikipedia, concerning poison gas use of chlorine, using a damp rag with urine instead of water to protect the nose: "as it was known at the time that chlorine reacted readily with urea (present in urine) to form dichlorourea."

Any ammonia present in urine can react with Cl2 to form NCl3, this could be risky depending on its quantity presence. Any sign of dense yellow droplets resembling in appearance olive oil are indicative of NCl3 in any probe trials, it's also not untypical to see pale yellow murkyness when it forms chemically.

[Edited on 10-1-2010 by Formatik]
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 Sciencemadness Discussion Board » Special topics » Biochemistry » Isolation of urea from urine! Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Detritus   » Test Forum