Examination of Essential Oils. 



13 



the spectrum. In other cases absorption bands are present because 

 -the oil itself is largely composed of some other benzene derivative. 



Thyme Hydrocarbon. No. 2. (Dr. Gladstone.) — After careful dis- 

 tillation and fractioning, there were two portions which boiled at 

 161-163°, and 163—170°. A considerable quantity derived of 

 course from the first fractions boiled between 162° and 163°, and was 

 taken as the representative of the pure substance. The liquid diluted 

 to 50, 500, 750, 1,000, 1,500, 2,000, 4,000, 8,000 and 16,000 times its 

 original volume was examined. (Diagram 11.) 



DlAGEAM 11. 



Thyme hydrocarbon. (Dr. Gladstone.) 



This absorption is due to the large amount of cymene contained in the liquid. 



The curve shown is interesting, because it enables us to make an 

 approximate estimation of the proportion of cymene contained in the 

 hydrocarbon, for since the absorption exhibited when the dilution to 

 tto coincides as nearly as possible with that given by cymene at 

 it is evident that the thyme hydrocarbon must contain about 

 ± its volume of this liquid. The rounding off of the more refrangible 

 portion of the spectrum is a modification caused by the terpene. 



u Hydrocarbon from Oil of Lemons. — Boiling point 343° F., specific 

 gravity 0'8468 at 20° C."* (Dr. Gladstone.) 



* Quotation from original label. 



