Mayer's reagent is an alkaloidal precipitating

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

used for the detection of

alkaloids Alkaloids are a broad class of naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids. Alkaloids are produced by a large variety of organisms i ...

in natural products. Mayer's reagent is freshly prepared by dissolving a mixture of

mercuric chloride Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...

(1.36 g) and of

potassium iodide Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...

(5.00 g) in water (100.0 ml). Most alkaloids are precipitated from neutral or slightly acidic solution by Mayer's reagent ( potassiomercuric iodide solution) to give a cream coloured precipitate. This test was invented by and named after the German chemist

Julius Robert Von Mayer Julius Robert von Mayer (25 November 1814 – 20 March 1878) was a German physician, chemist, and physicist and one of the founders of thermodynamics. He is best known for enunciating in 1841 one of the original statements of the conservation ...

(1814–1878).

References

Potassium compounds Mercury(II) compounds Alkaloids Chemical tests Drug testing reagents {{alkaloid-stub