Mayer s Reagent

Mayer s reagent (gives white precipitate with most alkaloids in a slightly acid solution) dissolve 13.55 g of HgCl2 and 50 g of KI in a liter of water. 

The remaining aqueous layer was then acidified with acetic acid a saturated aqueous solution of ammonium reineckate was added to a portion, but no precipitation occurred. No precipitate was noted with Valser s or Mayer s reagent. 

Mercuric-Potassium Iodide TS Mayer s Reagent) Dissolve 1.358 g of mercuric chloride (HgC ) in 60 mL of water. Dissolve 5 g of potassium iodide (KI) in 10 mL of water. Mix the two solutions, and add water to make 100 mL. 

Use Medicine (antiseptic), analytical reagents (Nes-sler s reagent, Mayer s reagent). 

Note Estimation of the alkaloid is done by Mayer s reagent and it corresponds to 0.038 gm of napelline to Ic.c of the reagent. 

In the CSIRO survey of Papua-New Guinea plants, a somewhat more elaborate testing method [19] was adopted finely ground plant material was extracted with ammoniacal chloroform, then the filtered extract was shaken with sufficient dilute acid to neutralise the ammonia and to extract any alkaloid present. The clarified acid solution was tested with Mayer s reagent, and the result rated as - or + to ++++ as in the case of Webb s surveys. The necessary equipment was designed to fit into a portable kit that could be taken into the field. The same procedure was used in some later screens of mainland Australian plants by the CSIRO [20] and in the surveys of orchidaceous plants [24, 25] also in the Tasmanian survey, with some modifications to make it more convenient under field conditions [22]. 

Incompot The vitamin is destroyed by alkalies and alkaline drugs such as phenobarbita] sodium and hy oxidizing and reducing agents. It is precipitated by tannins (which occur in wine) and by reagents which precipitate alkaloids, e.g. Mayer s reagent, mercuric chloride, picric acid, iodine. For stability in dry prepns Over several years see Partington, Waterhouse, J. Pharm. Pharmacol. 5, 715, 721 (1953). Chemical fate in alkaline solns Maier, Metzler, J. Am,... 

At this stage a cursory test for the presence of alkaloids in the extract is in order. Mayer s reagent (potassium mercuric iodide solution) has proved very satisfactory, for it yields a precipitate with virtually all alkaloids. Unfortunately, the formation of precipitates by this reagent is not diagnostic for this group of natural products alone since plant extracts which are entirely free of alkaloids often give precipitates. Hence a positive test with this reagent must be interpreted with caution. 

Mayer s reagent (white precipitate with most alkaloids in slightly acid solutions). Dissolve 1.358 g of HgCl in 60 mL of water and pour into a solution of 5 g of KI in 10 mL of H O. Add sufficient water to make 100 mL. 

The aqueous solution (A) contained the non-extractable quaternary bases. It was acidified with hydrochloric acid, filtered and precipitated with concentrated Mayer s reagent (50 g. of mercuric chloride, 200 g. of potassium iodide, 400 cc. of water), added with constant stirring. The precipitate was filtered, suspended in hot water, and hydrogen sulfide was bubbled through the suspension until all the mercury was precipitated as sulfide. The hot filtered solution on cooling yielded candicine iodide (hordenine methiodide) in straw-colored needles. The salt was recrystallized from hot water with the aid of charcoal and yielded colorless crystals, which melted at 234°. The mother liquors contained only small amounts of candicine. Total yield 16.4 g. of candicine iodide 2% of candicine on the dry plant. 

Candicine, like other quaternary compounds, cannot be extracted from alkaline solution with immiscible solvents. It was isolated by precipitating the purified plant extract with concentrated Mayer s reagent and then decomposing the precipitated mercuriiodide with hydrogen sulfide, the base being recovered in the form of its slightly soluble iodide. 

Detection, analysis A. precipitation reagents that effect formation of poorly water soluble salts are, e.g., Dragendorff s, FrOhde s, and Mayer s reagents, picric acid, picrolonic acid, dipicrylamine, phosphomolyb-dic acid, Reinecke s salt, and sodium tetraphenylbo-rate. Special color reactions are used for some groups of A., e.g., Vitali s reaction to detect tropane A., the thalleioquine reaction for Cinchona A., the murexide reaction for purines. 

For preparative purposes, purifications based on the precipitation of alkaloids are sometimes employed. A crude extract of the alkaloids is made with aqueous acid, subsequently the alkaloids are precipitated with reagents such as Mayer s reagent (IM mercury chloride in potassium iodide) or Reinecke s salt (5% ammonium reineckate in 30% acetic acid) at pH 2, or picric acid (saturated aqueous solution) at pH 5-6. After collection of the precipitate by filtration or centrifugation, the precipitate is dissolved in an organic solvent (acetone-methanol-water 6 2 1). The complexing group is then removed by means of an anion exchanger (Jordan and Scheuer 1965 Verpoorte and Baerheim Svendsen 1976). This method is particularly suited for the purification of quaternary alkaloids. 

Based on the isolation procedure followed, one can conclude with some degree of certainty whether an isolated compound is an alkaloid or not. Particularly acid/base extraction schemes result in rather specific extraction of alkaloids. Moreover, several reagents that react specifically with alkaloids have been described, e.g., Dragendorffs reagent, potassium iodoplatinate, Mayer s reagent. The first two reagents mentioned are also used as detection... 

Mayer s test A general presumptive test for cocaine, morphine, heroin, and other alkaloids. Mayer s reagent is a solution of potassium mercury iodide in water. A positive result is indicated by a cream precipitate. 

CiiHi N.Clj, MW, 243. m.p. 137. HNO, green col. (nitroso-comp.). Acid sol. give with Mayer s reagent. 

Ricinine, C5H8O2N2, was isolated by Tuson from castor-oil seed and was subsequently examined by Soave, Schulze and Evans. It crystallises in prisms, m.p. 201-5°, sublimes at 170-180°/20 mm., is neutral in reaction, optically inactive, and forms no salts. It is precipitated by solutions of iodine or mercuric chloride, but not by Mayer s reagent. Evaporated with nitric acid it leaves a yellow residue, which becomes purple on addition of ammonia solution. 

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