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BAM R38: Kovacs' Reagent

January 2001

Bacteriological Analytical Manual

Kovacs' Reagent


p-Dimethylaminobenzaldehyde 5 g
Amyl alcohol (normal only) 75 ml
HCl (concentrated) 25 ml


Dissolve p-dimethylaminobenzaldehyde in normal amyl alcohol. Slowly add HCl. Store at 4°C. To test for indole, add 0.2-0.3 ml reagent to 5 ml of 24 h bacteria culture in tryptone broth. Dark red color in surface layer is positive test for indole.


Original Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998