Uracil,
C4H4N2O2—112.09 [66-22-8]—White to cream-colored, crystalline powder. Melts above 300
. One g dissolves in about 500 mL of water; less soluble in alcohol; soluble in ammonia TS and in sodium hydroxide TS. Its solutions yield no precipitate with the usual alkaloidal precipitants.
C4H4N2O2—112.09 [66-22-8]—White to cream-colored, crystalline powder. Melts above 300. One g dissolves in about 500 mL of water; less soluble in alcohol; soluble in ammonia TS and in sodium hydroxide TS. Its solutions yield no precipitate with the usual alkaloidal precipitants.
Residue on ignition (Reagent test):
negligible, from 100 mg.
negligible, from 100 mg.
Loss on drying 
731
—
Dry it at 105 for 2 hours: it loses not more than 2% of its weight.
731—
Dry it at 105 for 2 hours: it loses not more than 2% of its weight.
Uranyl Acetate
(Uranium Acetate),
UO2(C2H3O2)2·2H2O—424.15 [541-09-3]—Use ACS reagent grade.
UO2(C2H3O2)2·2H2O—424.15 [541-09-3]—Use ACS reagent grade.
Urea,
NH2CONH2—60.06 [57-13-6]—Use ACS reagent grade.
NH2CONH2—60.06 [57-13-6]—Use ACS reagent grade.
Urethane
(Ethyl carbamate),
C3H7NO2—89.09 [51-79-6]—White powder with chunks. Freely soluble in water.
C3H7NO2—89.09 [51-79-6]—White powder with chunks. Freely soluble in water.
Melting range 741:
between 48 and 50.
741:
between 48 and 50.
Uridine,
C9H12N2O6—244.20 [58-96-8]—White powder.
C9H12N2O6—244.20 [58-96-8]—White powder.
Assay—
mobile phase—
Prepare a mixture of methanol and 0.2 M ammonium acetate (90:10), and adjust with phosphoric acid to a pH of 7.0.
test solution:
0.5 mg per mL.
procedure—
Inject about 20 µL of the Test solution into a liquid chromatograph (see Chromatography 621), equipped with a 280-nm detector and a 4.6-mm × 15-cm column that contains packing L1. The flow rate is about 2.0 mL per minute. The area of the C9H12N2O6 peak is not less than 99% of the total peak area.
mobile phase—
Prepare a mixture of methanol and 0.2 M ammonium acetate (90:10), and adjust with phosphoric acid to a pH of 7.0.
test solution:
0.5 mg per mL.
procedure—
Inject about 20 µL of the Test solution into a liquid chromatograph (see Chromatography 621), equipped with a 280-nm detector and a 4.6-mm × 15-cm column that contains packing L1. The flow rate is about 2.0 mL per minute. The area of the C9H12N2O6 peak is not less than 99% of the total peak area.
Melting range 741:
between 166 and 171.
741:
between 166 and 171.