- Chen-Kao test: To 1 ml of a solution of the substance add an equal volume of an alkaline solution of copper sulphate (0.1 ml of 10% CuSO4 and 1 ml of 20% NaOH). The solution turns violet due to the formation of a violet-coloured complex between ephedrine and copper sulphate in alkaline medium. While only ephedrine and pseudoephedrine give a violet colour, norephedrine and norpseudoephedrine and related compounds give a bright blue-coloured precipitate.
- Simon’s test: To 1ml of a solution of ephedrine in water add an equal volume of Simon’s reagent (sodium nitroprusside in a basic buffer). Formation of a bright blue colour that deepens on standing is obtained. This is characteristic of an amine.
- Pesez’s test: A small quantity of ephedrine dissolved in 2 ml concentrated H2SO4 develops a pink to red colour when 3 to 4 drops of 40% formaldehyde are added. Upon warming the colour changes to wine-red.
- A slightly alkaline solution of ephedrine when warmed with a drop of a 1% solution of ninhydrin gives a violet colour soluble in amyl alcohol.
- Erdmann’s reagent: Solutions of ephedrine with a mixture of sulphuric and nitric acids (Erdmann’s reagent) give a yellow ring below and a pink ring with a smoky pink layer on the top.
- Mayer’s reagent: To 1ml of a solution of ephedrine add Mayer’s reagent. The solution becomes cloudy on standing.
- Wagner’s reagent: To 1ml of a solution of ephedrine add Wagner’s reagent. An orange precipitate is formed.
- Solution of ephedrine with phosphor molybdic acid gives a greenish-yellow heavy precipitate which turns blue on standing.
- With phosphotungstic acid solutions of ephedrine give a heavy white precipitate.
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