— 40 — 4 



In the last Bericht of Roure-Bertrand Fils, J. Dupont and L. Labaune l ) 

 recommend a method for the direct estimation of geraniol in citronella oil. 



The basis of this method is that the citronellal is first converted into 

 its oxime; the oil is then acetylated, and after this the ester-value of the 

 acetylated oil is determined. When the oximated oil is heated with acetic 

 anhydride the citronellal oxime is converted into the nitrile of citronellic 

 acid which, under saponification, is stable towards the alkali. Hence only 

 the alcoholic constituents react, but these of course do not represent 

 only the geraniol which is present, but the total alcohols of the oil. 

 Dupont and Labaune proceed as follows: 10 g. citronella oil are first 

 shaken up at ordinary temperature (15 to 18°) for 2 hours with a hydroxyl- 

 amine solution 2 ). The oximated oil is then again dried and subsequently 

 acetylated. The geraniol-content is next estimated from the ester-value 

 of the acetylated oil and the citronellal-content by subtraction from the 

 so-called total geraniol. As the molecular weights of citronellal (154) and 

 of the nitrile of citronellic acid (151) correspond very nearly, the conversion 

 of citronellal may be disregarded in the calculation. The citronellal re- 

 generated from the bisulphite compound which the authors employed in 

 their experiments was first tested by them for purity by the method above- 

 described; this manipulation showed that 2,5 p. c. of an alcohol Ci Hi 8 O, 

 doubtless isopulegol, were present. Taking this source of error into 

 account, the authors obtained correct values for artificial mixtures of 

 geraniol and citronellal. 



Dupont and Labaune found a Ceylon citronella oil to contain: so-called 

 total geraniol 60,2 p. c, geraniol 43 p. c, citronellal 60,2 — 43 = 17,2 p. c. 

 In a Java oil 3 ) they found: so-called total geraniol 83 p. c, geraniol 43 p. c, 

 citronellal 83 — 43 = 40 p. c. 



Such a method, provided it gives useful results, is undoubtedly of 

 great practical value. We have therefore thoroughly investigated it, re- 

 peating in part the experiments described and partly carrying out new 

 manipulations which appeared to us to be necessary. As the authors 

 adopt a somewhat different acetylation method, (they heat the oil l 1 / 2 hours 

 with double its volume of acetic anhydride without the addition of sodium 

 acetate), we have also carried out this method, in which we have found, 

 that although geraniol may be acetylated quantitatively without sodium 

 acetate, citronellal can only be very imperfectly acetylated in this way. 

 Of an entirely pure preparation (di 5 o 0,8562; a D -\-\0° 42') only 25,5 p. c. 

 was converted into ^sopulegyl acetate by this method. And although it 

 does not matter much whether the acetylation of the oil freed from citron- 



*) Berichte von Roure-Bertrand Fils, April 1912, 3 



2 ) Hydroxylamine solution: dissolve 10 g. hydroxylamine hydrochloride and 12 g. potas- 

 sium carbonate each in 25 g. water, mix the solutions, and filter. 



3 ) In Java citronella Oil, Dupont and Labaune detected two new constituents: isoamyl- 

 alcohol and isovaleraldehyde. 



