Zeisel’s method

Naphthyl methyl ether.—Dissolve 3-6grams(3-naphthnl in I3 5 c.c. 10 per cent, caustic soda solution, add 3 c.c. meth l sulphate, warm the liquid gently and shake vigorously. In. i short time the naphthyl methyl ether separates as a solid mass. The product is heated for ten minutes on the water-bath, a little water is added, and the naphthyl ether filtered and washed with water. It is crystallised from alcohol and deposits in lustrous plates m. p. 70—72°. The yield is theoretical. It may be used for analysis by Zeisel s method. 

The methyl of the CHsO group is converted into methyl iodide (Zeisel s method) by boiling with hydriodic acid and the methyl iodide is converted into the corresponding bromide with formation of iodine bromide ... 

Salicylic acid is orthohydroxybenzoic acid. Metahydroxybenzoic acid was discovered by B. W. Gerland by the action of nitrous acid on meta-amino-benzoic acid, parahydroxybenzoic acid by C. Saytzeff by heating anisic acid (methylparahydroxybenzoic acid) with hydriodic acid — a precursor of Zeisel s method (see p. 871), and G. Fischer from para-aminobenzoic acid, which he discovered by the action of ammonium sulphide on paranitrobenzoic acid. Kolbe obtained the para-compound by passing carbon dioxide over potassium phenoxide at i7o°-2io° (sodium phenoxide gives only a small yield). 

Zeisel s method does not distinguish between me-thoxyl and ethoxyl should this be necessary, the alkyl iodide must be prepared in quantity sufficient for its... 

Citraptene contains two methoxyl groups when treated by Zeisel s method to remove the methyl groups, the demethylated citraptene, iCglLO, yields phlorogludn and acetic acid on fusion with alkali. 

Zeisel s method is used to determinate methoxy and ethoxy groups. It is a method of both qualitative and quantitative organic analysis. It is mentioned under the heading General Methods of Analysis of the 10th edition of the french pharmacopeia. It ends with an argentometric titration. Its principle is based on the reaction of hydroiodic acid (Berthelot s universal reductor) with ether oxides, according to the reactions... 

Cumming s Modification.—(J. S. 0.1., 41, 20.)—A convenient apparatus for the estimation of methoxyl groups by the Zeisel method consists of a long-necked round-bottomed flask attached by a ground-glass joint to a bulbed U-tube. The methyl iodide generated by the interaction of hydriodic acid and the methoxyl group is absorbed in alcoholic silver nitrate. Pyridine may also be used as absorbent. (J. C. S., 117, 193.) For purification of hydriodic acid, see p. 506. 

The Zeisel method is based upon the fact that alkoxyl groups, whether in ethers or esters, are decomposed by heating with strong hydriodic acid to jneld alkyl iodides. The latter are absorbed in alcoholic AgNO.s and estimated as Agl. ... 

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