You may have heard that the sting of a jellyfish can be treated with human urine, but in truth, all this is likely to achieve is establishing an awkward relationship between you and your dive instructor. In fact, a well-hydrated urine sample can actually trigger the stinging nematocysts deployed by the jelly to release more venom, causing you more pain. To the modern human, urine has little worth beyond medical investigations (unless you’ve bought any dodgy perfumes lately), but in the past, humans had many uses for pee.
Human urine contains urea – an organic compound rich in nitrogen that, left to its own devices, eventually breaks down into ammonia. Combine that with water and you've got a basic fluid with a high pH. As a result, it’s good at blasting acidic grime, and its cleansing properties were not overlooked in ancient Rome where the public was encouraged to relieve themselves into communal vessels so that the stain-busting pee could be delivered to an early version of a launderette, known as a fullonica. Here, one lucky fullo would stand in a pit of dirty clothes soaked with diluted urine and stamp away the stains. A covetable career, I’m sure.
The cleaning properties of urine endured even after the invention of soap, with “chamber lye” constituting a popular agent for soaking tough stains. It wasn’t just effective at cleaning clothes either, it also enabled and maintained dyed materials. There are many natural dyes derived from flowers, bark, and berries. Although they can easily leave a stain, getting the dye to remain requires a mordant – a complex molecule that can cocoon a colorant, effectively binding it to the cloth. Ammonia in the form of old urine is one such mordant, wrapping around colors to stop them from leaching out.
A more explosive use for human urine was gunpowder, a chemical used in ballistics that needs a healthy dose of potassium nitrate to be effective. As luck should have it, our pee contains nitrogen. As if exploding pee particles isn’t an offensive enough agent to die by, an eye-opening manual by physician Joseph LeConte in 1862 detailed the recipe for saltpeter (aka potassium nitrate) that called for “a good supply of thoroughly rotted manure of the richest kind.”
This precious commodity was stacked in a hellish heap with ash, straw, and leaves where the fun continued. “The heap is watered every week with the richest kinds of liquid manure, such as urine, dung-water, water of privies, cess-pools, drains... The quantity of liquid should be such as to keep the heap always moist, but not wet,” (after all, a wet poo-pee-pile would be going too far). After several months, the heap needn’t be moistened with urine any longer, as the appearance of a “whitish efflorescence,” signaled the saltpeter-seeker’s torment was almost nigh – a simple taste test could confirm the presence of potassium nitrate.
If sampling urine-soaked dung heaps isn’t your bag, then get ready to turn that frown upside-down with a recipe for a glowing smile. We’re back with ancient Rome for a teeth-whitening cure for the ages, as these resourceful DIY dentists leaned on the stain-busting power of ammonia to clean their mouth bones. Before you go reaching for a glass of the gold stuff, it’s perhaps pertinent to mention that thanks to a German chemist called Friedrich Wöhler, you can now source urea without going via a kidney. After mixing silver cyanate with ammonium chloride, Wöhler realized he had created white crystals that carried all the benefits of urea without the urethra. Nice one, Wöhler.