— 142 — 



among other things, why different investigators have in the past obtained 

 different results 1 ). * 



Another serious error lies in the incorporation of the colour-reaction 

 which was recommended at the time by Conrady for testing sandalwood 

 oil. We have repeatedly pointed out 2 ) that this reaction is quite useless 

 for sandalwood oil evaluation. 



Chemical Preparations and Drugs. 



Aldehydes, Higher. It has been ascertained (chiefly in our labo- 

 ratories), that the characteristic carriers of the odour of a large number 

 of oils of the first practical importance in perfumery and in the manufacture 

 of essences are a series of the so-called higher aldehydes. These alde- 

 hydes have been named after the number of carbon-atoms contained in 

 them and among them the following have been found to occur in essential 

 oils: octylaldehyde (with eight carbon-atoms, C 8 ) in lemon oil; nonyl- 

 aldehyde, C 9 , in German rose oil, Ceylon cinnamon oil, mandarin oil, 

 orris root oil, and probably also in lemon oil; decylaldehyde, Cio, in 

 sweet orange oil, lemongrass oil, mandarin oil, orris root oil, neroli oil, 

 cassie flower oil; duodecylaldehyde or laurinaldehyde, C12, in pine needle 

 oil from Abies pectinata. 



Although these aldehydes occur only in fractions of one per cent they 

 are of very material importance in determining the odour of the oil. They 

 all possess a marked odour peculiar to themselves, and generally of a 

 refreshing, fatty-sweet character, somewhat varying, of course, in each 

 member of the series. The particular shade of odour peculiar to each 

 separate aldehyde only becomes perceptible in high dilution, as, for in- 

 stance, in alcoholic solution. 



We have now incorporated into our lists a series of these higher 

 aldehydes, namely octylaldehyde, nonylaldehyde, decylaldehyde, undecyl- 

 aldehyde, and duodecylaldehyde (laurinaldehyde). The applicability of the 

 aldehydes may be inferred in part from their occurrence in the natural 

 oils, as stated above, that is to say, they can be used in the first place 

 in the preparation of the corresponding synthetic oils, such as sweet 

 orange oil (decylaldehyde), lemon oil (octyl- and nonylaldehyde), rose oil 

 (nonylaldehyde) and so on. Further, according to recent experiments /»y 

 leading French perfumers, some of the aldehydes in question will find 

 a new field of usefulness in the preparation of fine perfumes. Duodecyl- 

 aldehyde, in particular, when added to «-ionone in proportions of 5% or 



x ) Comp. Gildemeister and Hoffmann, The Volatile Oils, p. 340. 

 2 ) Report October 1897, 54; April 1904, 82. 



