112 — 



benzaldehyde, the proportion of that body which is present may be 

 calculated. The method is said to give accurate results, and to be 

 applicable also to bitter almond oil. 



In a paper read by S. H. Baer 1 ) before the Association of 

 Official Agricultural Chemists on November 8 th 1908, the author points 

 out that there is no practical method for the analysis of "terpeneless 

 lemon extract" based upon the determination of the citral content, 

 and that consequently an unobjectionable method for fixing standard 

 values for the product in question is rendered very difficult. Offici- 

 ally a content of at least 0,2 °/ of citral, which must be obtained 

 from oil of lemon, is demanded. As for analytical investigations com- 

 mercial citral, obtained from lemongrass oil, is mostly used, Baer 

 thinks it desirable that citral from oil of lemon should be taken as 

 the basis for analytical investigations, especially because citral may 

 exist in isomeric forms. Baer goes on to criticise some of the methods 

 proposed for the determination of citral. As the most suitable method 

 he regards one in which the distilling -off of alcohol and water is 

 obviated and in which the small quantities of citral could be separated 

 from the highly diluted aqueous alcoholic solution by means of a 

 solid derivative for gravimetric determination. For this purpose the 

 bisulphite compound or the semicarbazone might perhaps be used. 

 According to the tests carried out by Baer, Ch ace's method 2 ) is 

 unsuitable in practice, if only because in manufacturing processes the 

 application of chemically pure citral, distilled water, and alcohol free 

 from aldehyde, is of course out of the question. Besides this, it would 

 be impossible to detect any adulteration with other aldehydes, such as 

 acetaldehyde. On these grounds, Baer opposes the official adoption 

 of Chace's method. 



On a method for the determination of thujone in liqueurs, see 

 oil of Wormwood, p. 92. 



Physical notes. 



J. W. Bruhl 3 ) has tested instances in which hydrocarbons with 

 conjugated ethenoid - linkings do not show the condition known as 

 "exaltation". As terpinene, which was recognised by Wallach 4 ) as 

 a mixture of zf 1 ' 3 - and zf^-dihydrocymene, showed a normal molecular 

 refraction, whereas the Zl 1 ' 3 -dihydrocymene prepared synthetically by 



*) American Perfumer 3 (1909), 205. 



2 ) Journ. Amer. chem. Soc. 28 (1906), 1472; Report April 1907, 116. 



3 ) Berl. Berichte 41 (1908), 3712. 



4 ) Liebig's Annalen 362 (1908), 293; Report November 1908, 174. 



