Urea

 

Urea
aka diamino carbonyl

Chemical formula	OC(NH2)2
Molar Mass(g/mol)	60
Density(g/cc)	1.32
Melting Point(°C)	135
Solubility in water(g/L)	≥1000
Solubility in ethanol(g/L)	50
NFPA 704	0 0 0
Thermal Decomposition	urea unk°C NH3,CO2

A major source of organic nitrogen.

Uses

Primary

• Industrial chemical
• Fertilizer (46-0-0)

Secondary

• Feedstock (through natural decomposition) to ammonia
• Feedstock for urea nitrate for cold packs
• Pharm: (ointment) Skin treatment

Natural occurrence

• Appears naturally in urine and to a lesser degree in compost

Production

Extraction

from urine

Approximately 9.3g are expected in a liter of fresh human urine. Delay in processing allows bacteria to convert the urea to ammonia.

simple evaporation

1. Dry urine to solids
2. Repeat
   1. Dissolve in ethanol
   2. filter
   3. discard residue
   4. evaporate alcohol
   5. gather crystals
3. Until nothing but clear crystals remains

The crystals are urea

further separation

Reactants

• Urine
• Calcium oxide
• Distilled water
• Ethanol

Products

• Urea
• Mineral salts rich in Sodium chloride (roughly sea salt)
• Organic sludge rich in phosphate and proteins

Equipment

• Liquid Dryer/Evaporater
• Gas bubbling equipment
• (Optional) Distillation equipment

1. Boil 10L of urine down to 1L (containing ~93g, 6.6M of urea)
2. Filter
3. Residue contains organics, calcium and other phosphates, can be retained to produce phosphorus or burned and disposed
4. Filtrate contains sodium chloride and urea
5. Evaporate water by gentle heating (≤ 133°C)
6. Residue is mostly sodium chloride and urea
7. Wash residue with hot concentrated ethanol several times, combine washings

   NB: Urea dissolves easily, salt does not.

8. IF (two layers form in the washings)
   1. Separate the aqueous layer and evaporate separately, producing mineral salts
9. ENDIF
10. Evaporate ethanol washings

    NB: It may be worth condensing the ethanol vapors

11. The residue is urea. It should crystallize

via oxalic acid

• Precipitate from urine using oxalic acid, then extract again using calcium hydroxide. Detoxify the calcium oxalate by thermal decomposition.

  CO(NH₂)₂ + H₂(COO)₂ → C₃H₆N₂O₅

  C₃H₆N₂O₅ + Ca(OH)₂ → CO(NH₂)₂ + Ca(COO)₂ + 2 H₂O

  Ca(COO)₂

  {

  →

  ≥600°C}

  CaCO₃ + CO

via nitric acid

1. Combine urine and nitric acid, producing urea nitrate crystals
2. Filter
3. Discard filtrate
4. Repeat
   1. Prepare a saturated solution of urea nitrate in boiling water
   2. Mix in charcoal fines
   3. Stir
   4. Cool
   5. Filter through charcoal
   6. Discard residue
   7. Dry solution to crystals
5. Until no further residue is collected and the crystals are as pure as desired

Synthesis

Wohler

• Combine silver cyanate with ammonium chloride.

  AgNCO + NH₄Cl → CO(NH₂)₂ + AgCl

See Also

• urease
• urine