A specific color reaction of glycolic aldehyde.

Procedure-To 1 cc. of the solution to be tested 2 cc. of the reagent are added in test-tubes of uniform size. The reagent consists of 800 mg. of diphenylamine (commercial preparation recrystallized from 70 per cent alcohol) in 80 cc. of glacial acetic acid (Baker’s Special for Shellac Analysis)’ and 0.55 cc. of sulfuric acid (c.P., Nand As-free). The mixture is shaken vigorously, and then the tubes are immersed in boiling water for 30 minutes. Solutions containing glycolic aldehyde in concentrations of as little as 1 mg. per cent show a grass-green color. Spec$icity of Reaction-Trioses show a characteristic brown color. Acetaldehyde and formaldehyde show a greenish yellow and in concentrations of above 0.005 per cent a turbidity. Fructose above 0.01 per cent produces a greenish blue color, while aldohexoses, pentoses, and methylpentoses do not show any appreciable color up to concentrations of 0.05 per cent. The green color seems to be specific for glycolic aldehyde.