Chemical Preparations and Drugs. 99 



the hind-legs. If the thymol stays for any length of time in the stomach or in the 

 intestins, it irritates the mucous membranes. Aristol (dithymoldiiodide) is soluble in 

 water and in the gastric juice. 



Vanillin. H. C. Sievers and L. Givaudan 6{ Co. 1 ) publish a method of preparing 

 vanillin from acetylisoeugenol by oxidation with sodium bichromate or chromic acid, 

 in the presence of amino-carboxylic acids. The addition of 1.5 to 2 per cent, of such 

 a amino-carboxylic acids as catalyst, for instance ^-amino-benzoic acid, has a favourable 

 influence on the oxidation and on the yield of vanillin. One proceeds as follows: 

 120 parts of isoeugenol are distributed in 1240 parts of a sodium bichromate solution 

 (250 parts in 1000 parts of water); under continuous stirring at a temperature of 80°, 

 a solution of 1.5 to 2 parts of ^>-aminobenzoic acid in 500 parts of 50 per cent, sulphuric 

 acid is allowed to flow in. As soon as the oxidation is completed the acetylvanillin 

 formed is extracted with a solvent and the vanillin obtained by way of the bisulphite 

 compound. One obtains 12 parts of unaltered acetisoeugenol and 68 parts of vanillin. 



The yield is the same if the amino-carboxylic acids are replaced by aromatic amino- 

 aldehydes, such as ^-amino-benzaldehyde 2 ). 



As to the manufacture of vanillin from guayacol and formaldehyde, see page 143 

 of this Report. 



Two samples of vanillin tested in our laboratories were grossly adulterated; one 

 containing about 55 per cent, of antifebrin, the other 75 per cent, of benzoic acid. 

 The adulterants influenced the melting point considerably, of course, for the preparation 

 containing antifebrin melted already between 64 and 68° (instead of at 82°), whereas 

 the other began to sinter at 68° and was completely melted only at 110°. 



The antifebrin was separated off by shaking the product, dissolved in ether, with 

 soda lye, when only the vanillin is taken up by the soda lye. The antifebrin remained 

 in the ether and was obtained by evaporating the solvent, it was recognized by its 

 melting point (113 to 114°) and by its isonitril reaction. 



The benzoic acid was separated in a similar way, only that in this case the vanillin 

 was removed from the ethereal by shaking it with bisulphite lye. The residue obtained 

 on evaporation of the ether melted at 121° and could be identified as benzoic acid 

 also by its other properties. 



Taking into consideration the difference of price between vanillin and these two 

 adulterants, one easily understands that the buyers of the article will have paid far too 

 much for it in spite of the apparently low price. 



The methods of vanillin determination in vanilla extracts 3 ), according to which lead 

 acetate is added to the dealcoholized extract and the aldehyde is the determined by 

 weight, often lead to inexact results. Either the vanillin obtained is not quite pure and 

 the figures are too high, or the purification causes losses. The method indicated by 

 Hiltner 4 ), who purifies the vanillin in the end through sublimation at 105°, is not perfect 

 either, as according to H. J. Wichmann 5 ) the aldehyde forms non-volatile decomposition 

 products, when heated for some length of time to the above temperature. Wichmann 

 heated pure vanillin for 3 to 6 hours at 105 to 108°, and obtained 4 to 5.6 per cent. 

 of non-volatile, yellowish-brown residues, most likely oxidation and decomposition pro- 



2 ) Sums Patent 89053 of April 16 th , 1921. — 2 ) Swiss Patent 91088 of October 17 th , 1921. Supplement 

 to 89053. — *) The alcoholic extract of vanilla is meant. — *) U. S. Bur. Chem. Bull. 152 (1912), 135; 162 

 (1913), &'}. — *) Journ. Ass. Offic. Agrie. Chem. 4 (1921), 479. 



7* 



