Verification of urea as biuret


Chemicals needed

Fehling solution

urea

sodium carbonate (or hydrate) GSGESUND.gif (476 Byte) Xi   R 36    S (2)-22-26

sodium hydroxide solution 7.5%  GSATZEND.gif (935 Byte) C    R 35     S (1/2)-26-37/39-45


Equipment needed

test tube
burner (preferably alcohol-)


Test procedure


Disposal


Elucidation

Through the thermic decomposition of urea biuret, inter alia, is formed. Together with Fehling solution this results in the characteristic coloration (biuret reaction).


Photos

DSCN0305.JPG (180912 Byte)

Thermic decomposition of urea

DSCN0308.JPG (171926 Byte)

Coloration due to biuret reaction


Literature

Derived from Versuch 1853 S, "Umwandlung des Harnstoffs beim Erhitzen", p. 323, [2]