— 120 — 



other hand, have made the same experience as we in checking this 

 method, and they also come to the conclusion that the linalool 

 determination carried out according to B o u 1 e z , does not give 

 reliable results. 



In connection with what we said in our last Report on the subject 

 of Boulez's method, we would now summarise our opinion on this 

 matter as follows: with terpineol, under suitable conditions, the results 

 obtained are satisfactory; but the accuracy with regard to the linalool 

 determination still leaves very much to be desired, although it must 

 be admitted that the results are much better if a diluent is used, than 

 if the undiluted oil is acetylated. It remains to be seen whether the 

 process can also by suitable modifications be rendered useful for the 

 determination of linalool. 



With regard to the determination of cineol in eucalyptus oils, 

 see under the heading Eucalyptus oil, p. 45. 



For the determination of aldehydes and ketones, 

 P. B. Rother 1 ) has worked out a new method. It is based on this, 

 that aldehydes and ketones are converted in phenyl hydrazones 

 by adding definite quantities of free phenyl hydrazin, the excess of 

 phenyl hydrazin added is brought into reaction with iodine, and the 

 iodine not used up is then titrated with thiosulphate solution. Ac- 

 cording to E. Fischer, iodine acts on phenyl hydrazin according to 

 the equation: — 



2 C 6 H 5 NH • NH 2 + 2 I 2 = C 6 H 5 N 3 + C 6 H 5 NH 2 . HI + 3 HI. 



But in the presence of an excess of iodine, the reaction, according 

 to E. v. Meyer, takes place as follows: — 



C 6 H 5 NH.NH 2 +2l 2 = C G H 5 I + N 2 + 3 HI. 



After experiments made by Rother with the view of detecting 

 possible sources of error, and which were made with reference to 

 changes in the standard of the phenyl hydrazin solution during the 

 time of testing, the influence of alcohol on the iodine starch reaction, 

 and the iodine action on the hydrazone formed, etc., the author finally 

 gives the following directions for carrying out the determination: — 



5 g. (fully) phenyl hydrazin are weighed out, dissolved in about 

 250 cc. warmed water, filtered in a 500 cc. flask for removing resinified 

 products, and filled up to the mark, after cooling, with boiled distilled 

 water. The solution keeps badly, and must be kept well-closed and 

 protected from light. 



1 ) According to a thesis kindly sent to us: Die Bestimmung der Aldehyde 

 und Ketone zur Bewertung atherischer Ole (The determination of aldehydes and 

 ketones for the valuation of essential oils). Dresden, 1907. 



