Urea was first noticed by Hermann Boerhaavein the early 18th century from evaporates of urine. In 1773,Hilaire Rouelle obtained crystals containing urea from dog's urine by evaporating it and treating it with alcohol in successive filtrations. This method was aided by Carl Wilhelm Scheele's discovery that urine treated by concentrated nitric acid precipitated crystals.
Antoine François, comte de Fourcroy and Louis Nicolas Vauquelin discovered in 1799 that the nitrated crystals were identical to Rouelle's substance and invented the term "urea." Berzelius made further improvements to its purification and finally William Prout, in 1817, succeeded in obtaining and determining the chemical composition of the pure substance.
In the evolved procedure,
urea was precipitated as urea nitrate by adding strong nitric acid to urine.
To purify the resulting crystals, they were dissolved in boiling water with charcoal and filtered.
After cooling, pure crystals of urea nitrate form.
To reconstitute the urea from the nitrate,
the crystals are dissolved in warm water, and barium carbonate added.
The water is then evaporated
and anhydrous alcohol added to extract the urea.
This solution is drained off and allowed to evaporate resulting in pure urea.
Comment from Forum:
I'm pretty sure that the "established" method of isolating urea from urine is to boil down the urine to concentrate the solution, then add nitric acid. Urea nitrate is relatively insoluble and precipitates. I think Megalomania's chem lab had a more exact procedure for this. Then you can take that small amount of solid and treat it with NaOH and ethanol to get the urea back.
I like this method because it should sharply separate urea from not-urea, and may require less energy (less forced evaporation). Urea oxalate is also fairly insoluble and can be precipitated from an aqueous solution containing urea.
Edit: sodium oxalate is isn't very soluble either, so I suppose HNO3 is the way to go.
Comment from Forum:
I'm pretty sure that the "established" method of isolating urea from urine is to boil down the urine to concentrate the solution, then add nitric acid. Urea nitrate is relatively insoluble and precipitates. I think Megalomania's chem lab had a more exact procedure for this. Then you can take that small amount of solid and treat it with NaOH and ethanol to get the urea back.
I like this method because it should sharply separate urea from not-urea, and may require less energy (less forced evaporation). Urea oxalate is also fairly insoluble and can be precipitated from an aqueous solution containing urea.
Edit: sodium oxalate is isn't very soluble either, so I suppose HNO3 is the way to go.
