REACTIONS AND IDENTIFICATION 363 crystalline urea nitrate, m.p. 163°, is precipitated, ( b ) To another portion, add concentrated aqueous oxalic acid solution: white crystals of urea oxalate, m.p. 171°, separate, particularly on scratching. Both salts dissolve in an excess of water. 4. Lrease test. The enzyme urease hydrolyses urea to ammonium car-bonate (p. 519). The reaction is sp" :ific and is frequently used for solu-tions of urea to which the biuret test cannot be applied. Add about 5 drops of phenol-red to 0-2 g. of urea dissolved in 5 ml. of water. To this yellow solution, add 0-2 g. of jack bean meal suspended in 2 ml. of water containing also 5 drops of phenol-red. The colour changes to red as the solution becomes alkaline. Oxamide. 1. Biuret test. Oxamide, having two CONH 2 groups, will give this test with-out any preliminary treatment (cf. urea). Shake o-i g. of oxamide with i ml. of 10% NaOH solution, add i drop of very dilute CuSO 4 solution and mix well. A rose-pink coloration is produced.
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.