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From Gunpowder to Teeth Whitener: The Science Behind Historic Uses of Urine | Surprising Science
The saying goes that one person’s waste is another’s treasure. For those scientists who study urine the saying is quite literal–pee is a treasure-trove of scientific potential. It can now be used as a source of electric power. Urine-eating bacteria can create a strong enough current to power a cell phone. Medicines derived from urine can help treat infertility and fight symptoms of menopause. Stem cells harvested from urine have been reprogrammed into neurons and even used to grow human teeth.
For modern scientists, the golden liquid can be, well, liquid gold. But a quick look back in history shows that urine has always been important to scientific and industrial advancement, so much so that the ancient Romans not only sold pee collected from public urinals, but those who traded in urine had to pay a tax. So what about pee did preindustrial humans find so valuable? Here are a few examples:
Urine-soaked leather makes it soft: Prior to the ability to synthesize chemicals in the lab, urine was a quick and rich source of urea, a nitrogen-based organic compound. When stored for long periods of time, urea decays into ammonia. Ammonia in water acts as a caustic but weak base. Its high pH breaks down organic material, making urine the perfect substance for ancients to use in softening and tanning animal hides. Soaking animal skins in urine also made it easier for leather workers to remove hair and bits of flesh from the skin.
The cleansing power of pee: If you’ve investigated the ingredients in your household cleaners, you may have noticed a prevalent ingredient: ammonia. As a base, ammonia is a useful cleanser because dirt and grease–which are slightly acidic–get neutralized by the ammonia. Even though early Europeans knew about soap, many launderers preferred to use urine for its ammonia to get tough stains out of cloth. In fact, in ancient Rome, vessels for collecting urine were commonplace on streets–passers-by would relieve themselves into them and when the vats were full their contents were taken to a fullonica (a laundry), diluted with water and poured over dirty clothes. A worker would stand in the tub of urine and stomp on the clothes, similar to modern washing machine’s agitator.
Even after making soap became more prevalent, urine–known as chamber lye for the chamber pots it was collected in–was often used as a soaking treatment for tough stains.
Urine not only made your whites cleaner, but your colors brighter: Natural dyes from seeds, leaves, flowers, lichens, roots, bark and berries can leach out of a cloth if it or the dyebath aren’t treated with mordant, which helps to bind the dye to the cloth. It works like this: molecules of dye called chromophores get wrapped inside a more complex molecule or a group of molecules; this shell housing the dye then binds to the cloth. The central nugget of dye is then visible but is protected from bleeding away by the molecules surrounding it. Stale urine–or more precisely the ammonia in it–is a good mordant. Molecules of ammonia can form a web around chromophores, helping to develop the color of dyes as well as to bind it to cloth.
Specific chamberpots dedicated to urine helped families collect their pee for use as mordants. Urine was so important to the textile industry of 16th century England that casks of it–an estimated amount equivalent to the urine stream of 1000 people for an entire year–were shipped from across the country to Yorkshire, where it was mixed with alum to form an even stronger mordant than urine alone.
Read more: http://blogs.smithsonianmag.com/science/2013/08/from-gunpowder-to-teeth-whitener-the-science-behind-historic-uses-of-urine/#ixzz2gcs8bZwS
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