Tuesday, October 11, 2011

Why Pee is Cool - entry #5 - "How Pee Unites You With Rocks"

From around the 2nd century onwards, many people subscribed to the doctrine of vitalism.  For alchemists, vitalism primarily meant that matter from the inorganic, inanimate world (crystals, rocks, etc) was fundamentally different from matter from the organic, living world (us, kittens, pee, etc).  Specifically, they believed that that non-living matter could not be transformed into living matter.  Vitalists held that the matter of life, the chemicals that compose living things, could be synthesized only by living things themselves.

In 1828 a German chemist named Friedrich Wöhler made a discovery that bridged the divide between living and non-living matter, and the story of how he did this starts of course with pee.

Friedrich Wöhler. German chemist/peepee enthusiast and 1828 blower of minds.

One liter of human pee contains about 20 grams of a nitrogen-containing chemical called urea.  Where does all this nitrogen come from?  Well, from the plants and animals we eat of course!  Their bodies contain nitrogen atoms mainly in the form of proteins, which they use for all sorts of things.  We pee out urea in order to dispose of all these nitrogen atoms--atoms that go in must come out.

We eat nitrogen atoms mainly in the form of protein, use them for various things, then eventually pee them out in the form of urea.

This may seem very simple now, but let's travel back in time to the 18th century when people knew waaaay less.  Sometime around 1727, Dutch scientist Herman Boerhaave was playing around with pee and became the first person to isolate urea.  His recipe called for boiling off all the water from "fresh, well-concocted urine of persons in perfect health" until it reaches the consistency of "fresh cream".  After squeezing out every last drop of liquid from this fresh-cream-of-urine, he put it "into a tall cylindrical vessel...for the space of a year".  Such patience!  After that year, the paste had turned into a solid mass on the bottom of the cylinder with some sort of mysterious oily substance on top.  He discarded the oil and rinsed the crystals with cold water to remove all the salts (NaCl, etc), leaving nearly pure urea that he then recrystallized from hot water to give the pure stuff.

Boerhaave's insane recipe for the isolation of urea from urine.  Please do try this at home.  On the right is a wicked microscope image from this recent publication in which they grew their crystals from water just like Boerhaave did almost 300 years ago!!!

So now people knew about urea, a pure substance that had something to do with animal life.  Still no philosopher's stone though, bummer.  Over the years people re-discovered urea and came up with better ways of isolating it from urine, so that any reasonably well-trained (al)chemist had access to the stuff.

Now what?  Well, as I said in 1828 Friedrich Wöhler came along and blew peoples' minds, that's what!!!  Instead of playing around with chemicals from the organic, living world, he was playing around with chemicals from the inorganic, dead world.  One day he was trying to do a simple reaction known as a salt metathesis between two chemicals known as inorganic salts.  He expected the ions in these inorganic salts to simply change places:

To his great surprise however, he isolated a chemical that behaved suspiciously like urea.

After doing a few experiments on his synthetic urea side by side with urea isolated from animals, he concluded he had indeed made a chemical from the living world out of a chemical from the non-living world.

After this discovery, Wöhler wrote to his mega-famous mentor Jöns Jacob Berzelius (1779-1848) and said:
I must tell you that I can make urea without the use of kidneys, either man or dog.
So understated!  Ultra-famous, mega-old chemist Justus von Liebig (1803-1873) struck a more momentous tone:
[The] extraordinary, and to some extent inexplicable, production of this substance without the assistance of the vital functions, for which we are indebted to Wöhler, must be considered one of the discoveries with which a new era in science has commenced.
The living and non-living worlds had been bridged for the first time in human history.  Our atoms are indistinguishable from the atoms of the rest of the earth.  WOAH!!!

This discovery did not however cause vitalists to completely give up and admit that living beings can in principle be fully explained through an understanding of their physical nature.  Instead vitalism itself gradually morphed into something that is more recognizable to us today.  Though many different people think many different things on this subject, Kurt Vonnegut summed up a view that seems pretty reasonable to me in his book "Breakfast of Champions":
Our awareness is all that is alive and maybe sacred in any of us. Everything else about us is dead machinery.
References & further reading: here, here, here, & here.

Related Posts:
PeePeePost #1: "Why Is Pee Yellow?" or "Rainbow of Urine"
PeePeePost #2: "Why Does Pee Smell?" or "Aroma of Life"
PeePeePost #3: "Explosive Urination" or "Gunpowder Comes from Pee!!!"
PeePeePost #4: "PeePee Portal to Phosphorus" or "What the Alchemists Did Right"
PeePeePost #6: "Pee, Our Connection with the Earth's Metabolic Cycle"


  1. Tremendous read, Lee. Thanks for putting it together.

  2. Psyched u enjoyed it! Thanks for reading!

  3. OK lee, this is post number 5 on urine. Don't get me wrong, each one has been awesome! Now I want to know what got you interested in pee.

    Thanks for the great blog!

  4. hahaha. It all started when I decided it was unacceptable for me to be a chemist and not know why my pee was yellow. Then I just started digging and the peepee discoveries just never seemed to end. Just one more post though and I will move on... to poop?? not sure yet.

    Thanks for reading!

  5. Aw man, I had a similar experience the other day... I made cream of cauliflower soup, using purple cauliflower. I tasted it and asked my roommate what she thought. After a sip, she said she'd kick it up a notch with a dash of lemon juice. The soup was a deep velvety purple color. When I squeezed the lemon juice into it, all the places it hit turned hot pink! It's embarrassing that 4 days later I am still thinking about it but have not taken the time to investigate or post the question on the ACS food chemistry forum. But I did get out a book on the chemistry and physics of color.

  6. Thanks wikipedia:

  7. That is awesome! What a sweet kitchen discovery! There is this easy/safe experiment you can do with kids, using the extract of red cabbage as a pH indicator:
    Turns out its the same types of chemicals in purple caulflower and red cabbage. I guess that shouldn't be too surprising, but shit like that always blows my mind.

  8. HA, I have a gut feeling that my cauliflower soup is hot pink in my stomach.