Urea

Action and use
Keratolytic

DEFINITION
Carbamide
Content
98.5 per cent to 101.5 per cent (dried substance).

CHARACTERS
Appearance
White or almost white, crystalline powder or transparent crystals, slightly hygroscopic.
Solubility
Very soluble in water, soluble in alcohol, practically insoluble in methylene chloride.

IDENTIFICATION
First identification A, B.
Second identification A, C, D.
A. Melting point: 132C to 135C.
B. Infrared absorption spectrophotometry.
C. Dissolve 0.1 g in 1 ml of water. Add 1 ml of nitric acid. A white, crystalline precipitate is formed.
D. Heat 0.5 g in a test tube until it liquefies and the liquid becomes turbid. Cool, dissolve in a mixture of 1 ml of dilute sodium hydroxide solution and 10 ml of water and add 0.05 ml of copper sulphate solution. A reddish-violet colour is produced.

TESTS
Solution S
Dissolve 10.0 g in water and dilute to 50 ml with the same solvent.
Appearance of solution
The solution is clear and colourless.
To 2.5 ml of solution S add 7.5 ml of water.
Alkalinity
To 2.5 ml of solution S add 7.5 ml of water, 0.1 ml of methyl red solution and 0.4 ml of 0.01 M hydrochloric acid . The solution is red to orange.
Biuret
Maximum 0.1 per cent.
Ammonium
Maximum 500 ppm, determined on 0.1 ml of solution S.
Heavy metals
Maximum 10 ppm.
Loss on drying
Maximum 1.0 per cent, determined on 1.000 g by drying in an oven at 105C for 1h.
Sulphated ash
Maximum 0.1 per cent, determined on 1.0 g.

DESCRIPTION
Urea occurs as a colorless to white, prismatic, crystalline powder or as small, white pellets. It is commonly produced from CO2 by ammonolysis or from cyanamide by hydrolysis. It is freely soluble in water and in boiling alcohol, but practically insoluble in chloroform and in ether. It melts at a range of 132C to 135C.
Function Fermentation aid.

REQUIREMENTS
Identification:
A. Heat about 500 mg of sample in a test tube until it liquefies. Ammonia vapor is produced. Continue heating until the liquid becomes turbid, and then cool. Dissolve the fused mass in a 1:10 sodium hydroxide solution:water mixture. Add 1 drop of cupric sulfate TS. A red-violet colored solution develops.
B. Dissolve 100 mg of sample in 1 mL of water, and add 1 mL of nitric acid. A white precipitate of urea nitrate forms.
Assay: Not less than 99.0% and not more than 100.5% of CH4N2O.
Alcohol-Insoluble Matter: Not more than 0.04%.
Chloride: Not more than 0.007%.
Lead: Not more than 5 mg/kg.
Loss on Drying: Not more than 1.0%.
Residue on Ignition: Not more than 0.1%.
Sulfate: Not more than 0.01%.

NH2CONH2
Formula Weight 60.06
CAS Number 57-13-6

REQUIREMENTS

MAXIMUM ALLOWABLE