|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