— 7o — 



always apply, if the specific gravity of the oil in question is suffici- 

 ently high. 



We are not yet prepared to express a definite opinion on what 

 has been stated above, as the material upon which the examinations 

 are based does not appear to us sufficiently voluminous to consider 

 the question as definitely solved. 



L. Vanino and F. Hartl 1 ) have found that some essential oils, 

 such as rosemary oil, which was formerly used for the manufacture 

 of Aurum potabile, and oil of turpentine, are eminently adapted 

 for the production of gold hydrosol. Solutions containing more than 

 0,0181 °/ gold, are, however, not suitable. The turpentine oil employed 

 must be pure. 



Rue Oil. Birckenstock's work 2 ) already quoted under lavender 

 oil also deals with oil of rue. French oil of rue [Ruta graveolens L.), 

 as is well known, differs from the Algerian oil by its congealing point. 

 Both contain about 9O°/ ketones, but the French oil almost exclusively 

 methylnonyl ketone (m. p. -j-i5°), and the Algerian methylheptyl ketone 

 (m. p. — 1 6°) 3 ). Morphological distinguishing characteristics of the two 

 plants do not exist. Birckenstock now has distilled Algerian rue 

 oil at three different vegetation periods, and has thereby made the 

 interesting observations that the differences in the compositions are 

 only attributable to the season in which the oils are distilled. Algerian 

 rue oil showed exactly the same composition and the same properties, 

 when it was, like the French, distilled in the autumn. This work of 

 Birckenstock's is supplemented by H. Carette's 4 ) examinations, 

 who states that two kinds of rue oil are produced in Algeria, which 

 differ in a marked degree from each other, and of which one is 

 designated "summer rue oil" ([from Ruta montana L.], consisting 

 chiefly of methylnonyl ketone, sol. p. between -|- 5 and -j-8°), and 

 the other "winter rue oil" ([from Ruta bracieosa L.], almost exclusively 

 consisting of methylheptyl ketone, sol. p. — 18 ). A rue plant de- 

 scribed as {e rue de Corse" was also found by Carette to be identical 

 with R. bracteosa) the sol. p. of the oil lay at — 15 , but it appears 

 to contain, in addition to methylheptyl ketone, large quantities of 

 methylnonyl ketone. According to Carette, the essential rue oils 

 of various origins can therefore be distinguished by isolating their 

 ketones with sodium bisulphite. An adulteration with turpentine oil 

 or petroleum can at once be detected by the fact that pure rue oils, 



*) Berl. Berichte 39 (1906), 1696. 



2 ) Moniteur scientifique Quesneville, May 1906. 



3 ) Report October 1901, 47; comp. also Report April 1901, 51. 



4 ) Journ. Pharm. et Chim. VI. 24 (1906), 58. 



