Hennig Brand’s experiments for the philosopher's stone with 5500 litres of Unine

Hennig Brand(t) (c. 1630 – c. 1710) was a merchant and alchemist in Hamburg, Germany who discovered phosphorus around 1669.Hennig Brand held a post as a junior army officer during the Thirty Years' War and his first wife's dowry was substantial, allowing him to pursue alchemy on leaving the army.

Like other alchemists of the time, Brand searched for the "philosopher's stone", a substance which purportedly transformed base metals (like lead) into gold. By the time his first wife died he had exhausted her money on this pursuit. He then married his second wife Margaretha, a wealthy widow whose financial resources allowed him to continue the search.

Like many before him, he was interested in water (H20) and tried combining it with various other materials, in hundreds of combinations. He had seen for instance a recipe in a book 400 Auserlensene Chemische Process by F. T. Kessler of Strasbourg for using alum, saltpetre (potassium nitrate) and concentrated urine to turn base metals into silver (a recipe which of course didn't work).

Around 1669 he heated residues from boiled-down urine on his furnace until the retort was red hot, where all of a sudden glowing fumes filled it and liquid dripped out, bursting into flames. He could catch the liquid in a jar and cover it, where it solidified and continued to give off a pale-green glow. What he collected was phosphorus, which he named from the Greek for "light-bearing" or "light-bearer."

Phosphorus must have been awe-inspiring to an alchemist. A product of man, and seeming to glow with a life force that didn't diminish over time (and didn't need re-exposure to light like previously discovered Bologna stone). Brand kept his discovery secret, again as alchemists of the time did, and worked with the phosphorus trying to use it to produce gold (unsuccessfully of course).

  • Boil urine to reduce it to a thick syrup.
  • Heat until a red oil distills up from it, and draw that off.
  • Allow the remainder to cool, where it consists of a black spongy upper part and a salty lower part.
  • Discard the salt, mix the red oil back into the black material.
  • Heat that mixture strongly for 16 hours.
  • First white fumes come off, then an oil, then phosphorus.
  • The phosphorus may be passed into cold water to solidify.

The chemical reaction Brand stumbled on was as follows. Urine contains phosphates PO43-, as sodium phosphate (ie. with Na+), and various carbon-based organics. Under strong heat the oxygens from the phosphate react with carbon to produce carbon monoxide CO, leaving elemental phosphorus P, which comes off as a gas. Phosphorus condenses to a liquid below about 280°C and then solidifies (to the white phosphorus allotrope) below about 44°C (depending on purity). This same essential reaction is still used today (but with mined phosphate ores, coke for carbon, and electric furnaces).

The phosphorus Brand's process yielded was far less than it could have been. The salt part he discarded contained most of the phosphate. He used about 5,500 litres of urine to produce just 120 grams of phosphorus.If he'd ground up the entire residue he could have got 10 times or 100 times more (1 litre of adult human urine contains about 1.4g phosphorus).

The Alchemist in Search of the Philosophers Stone (1771) by Joseph Wright depicting Hennig Brand discovering phosphorus (the glow shown is exaggerated)
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