Uracil,
C4H4N2O2112.09—White to cream-colored,crystalline powder.Melts above 300.One g dissolves in about 500mLof water;less soluble in alcohol;soluble in ammonia TSand in sodium hydroxide TS.Its solutions yield no precipitate with the usual alkaloidal precipitants. Residue on ignition(Reagent test): negligible,from 100mg. Loss on drying á731ñ Dry it at 105for 2hours:it loses not more than 2%of its weight.
Uranyl Acetate
(Uranium Acetate), UO2(C2H3O2)2·2H2O—424.15—Use ACSreagent grade.
Urea,
NH2CONH260.06—Use ACSreagent grade.
Urethane
(Ethyl carbamate), C3H7NO289.09—White powder with chunks.Freely soluble in water. Melting range á741ñ: between 48and 50.
Uridine,
C9H12N2O6244.20—White powder. Assay— MOBILE PHASE— Prepare a mixture of methanol and 0.2Mammonium acetate (90:10),and adjust with phosphoric acid to a pHof 7.0. TEST SOLUTION: 0.5mg per mL. PROCEDURE— Inject about 20µLof the Test solutioninto a liquid chromatograph (see Chromatography á621ñ),equipped with a 280-nm detector and a 4.6-mm ×15-cm column that contains packing L1.The flow rate is about 2.0mLper minute.The area of the C9H12N2O6peak is not less than 99%of the total peak area. Melting range á741ñ: between 166and 171.