The Baljet reaction is a qualitative and quantitative method of analysis published by Henri Baljet [1] in 1918. [2] This chemical reaction is used for the detection and colorimetric [3] determination of cardenolides. To the sample, an aqueous hydroxide solution and an ethanolic picric acid solution is combined and added, with a positive test turning orange or red. [4] [5] [ better source needed ] The mechanism involves cardenolides 1 reacting in alkaline solution with picric acid 2 to form stabilized Meisenheimer complexes, as shown with the resonance form 3a to 3c:
