Gmelin's reaction

A r. shown by biliary matter when 3 or 4 parts of urine are put into a conical gla ve el and 1 part of a mixture of equal parts of 25 per cent, nitric acid and red fuming nitric acid is poured slowly down the side of the ve el. Green, blue, violet, and yellow colors form where the acid collects at the bottom. G's test for bile in urine, see in appendix, page 894. G's test for bile pigments. By stratifying a solution of nitric acid containing some nitrous acid under an alkaline solution of bile, a series of colors is obtained at the junction of the two liquids in order from above downward, green, blue, violet, red, and reddish yellow. The reaction is due to the presence of the bilirubin in the bile. [Leopold Gmelin, Ger. physiologist, 1788-1853.]