An organic compound whose empirical and molecular formula are same, contains 20% carbon, 6.7% hydrogen, 46.7% nitrogen and the rest oxygen. On heating it yields ammonia, leaving a solid residue. The solid residue gives a violet colour with dilute solution of alkaline copper sulphate. The organic compound is

Empirical formula = Molecular formula $={\mathrm{CH}}_4{\mathrm{N}}_2\mathrm{O}\text{ or }{\mathrm{NH}}_2{\mathrm{CONH}}_2$

${\mathrm{H}}_2{\mathrm{NCONH}}_2+{\mathrm{H}}_2{\mathrm{NCONH}}_2\stackrel{\mathrm{\Delta }}{⟶}{\mathrm{H}}_2{\mathrm{NCONHCONH}}_2+{\mathrm{NH}}_3$

When an aqueous solution of biuret is treated with dilute sodium hydroxide and a drop of copper sulphate, a violet colour is produced. This test is known as biuret test.