Field of Science

The Treasures of Urine

Michelle Clement's post on What can urine tell us? has arrived at an opportune time. I am reading John Emsley's The Shocking History of Phosphorus and much of the first chapter is about the discovery of phosphorus from urine.

Alchemists of the day were desperately and highly secretively searching for the philosopher's stone. Henning Brandt, the discoverer of phosphorus, thought because urine is golden there must be something in it which make is to golden. Possibly gold?

In his attempts to isolate gold out of urine, Brandt evaporate urine to a paste and heated the residues hard to find shining vapours rising from it. When condensed he found that the shining liquid burst into flames if brought in contact with air. So he started collecting the vapours under water instead. The waxy, white solid that formed at the bottom was phosphorus.

So why phosphorus from urine? We tend to eat a lot more phosphorus than is needed by our body. So most of it is excreted.
A typical sample of urine from an adult male contains (per litre) - 52 g creatine, 21 g urea, 6.5 g chloride, 4 g sodium, 2.2 g potassium, 2.3 g amino acids, 1.4 g phosphorus, 0.7 g ammonia and  0.3 g magnesium.
Although Brandt had discovered this light-giving element in 1669, he did not divulge the method of obtaining phosphorus until 1678, by which Johann Kunckel, professor at the University of Wittenberg, had succeeded to isolate phosphorus and was touring the  European royal courts showing off the element and claiming to be its discoverer.

For many years it was thought that Kunckel discovered phosphorus, until papers from Leibniz (yes, the same calculus guy!) revealed that he had conversed with Brandt's wife about the discovery of phosphorus and which finally gave credit to the its true discoverer.

It seems that for at least a hundred after its discovery, urine remained the only source to obtain elemental phosphorus. Even today 3 million tonnes (worth ~$1 billion) of phosphorus is obtained from human excreta. Such are the treasures of urine.

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