Mayer's reagent

{{short description|Helps to detect alkaloids}}

Mayer's reagent is an alkaloidal precipitating reagent used for the detection of alkaloids in natural products. Mayer's reagent is freshly prepared by dissolving a mixture of mercuric chloride (1.36 g) and of potassium iodide (5.00 g) in water (100.0 ml).{{cite web | url = http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=00665%7CFLUKA&N25=0&QS=ON&F=SPEC | title = Mayer′s reagent | publisher = Sigma Aldrich | accessdate = 2012-02-08 | quote = K2HgI4}}{{cite web | url = http://www.pharmacopeia.cn/v29240/usp29nf24s0_ris1s126.html#usp29nf24s0_ris1s277 | title = Test Solutions | publisher = US Pharmacopeia | accessdate = 2012-02-08}} 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 (1814–1878).