ESSENTIAL OILS 



195 



The determination of these constants enables us to classify 

 oils into first and second grades. The limits for these grades 

 are given in Table 32. 



Table 32. — Classification of ilang-ilang oil according to Bacon. 



Constants. 



First grade. 



100 and above . 



Esternumber - 



Index of refraction 1.4900 and below. 



Specific rotation i —45° and below .. 



Second grrade. 



80 to 100. 

 Above 1. 4900. 

 Above-45°. 



In a later publication Bacon showed that first-grade oils have 

 a higher acetyl number than second-grade oils. 



The classification of ilang-ilang oil now in use is a modifica- 

 tion of Bacon's standard of classification, which was proposed 

 by Dr. Jaehrling of the firm of Santos and Jaehrling of Manila, 

 and advocated by Gibbs.* The constants of this classification 

 are given in Table 33. This classification divides Bacon's first 

 class into three divisions, namely: extra, 1-a, and 1-b. This 

 division is apparently necessary on account of the large pro- 

 portion of high-grade oil which is now produced. 



Table 33. — Classification of ilang-ilang oil according to Jaehrling. 



The solubility of ilang-ilang in alcohol is also given as an 

 extra test. According to Gibbs, this is very useful as a con- 

 firmatory test, since it indicates the amount of sesquiterpenes 

 present in the oil. This test consists in determining the lowest 

 strength of aqueous alcohol which can be mixed with the oil 

 without cloudiness, in the proportion of 2 of oil to 1 of alcohol. 



Bacon suggests an easy method of judging approximately the 

 quality of an oil: 



* Gibbs, H. D., Proposed modification of ilang-ilang oil standards. Phil- 

 ippine Journal of Science, Section A, Volume 10 (1915), page 99. 



