" Sfrivf/i/licrl," Ivnc(iiyi>ffi. 



179 



Fi"-. I. 





lo()°C 



2()() I 27ii 

 Aronuidendrene. 



2«(» 



cl-pineiie. l-piuene. Phellan- Eiicalyptol. 

 drene. 

 1). = E. dextropinea (d = -877, a = + 38°). E. = E. cagenioidcs (d = -913, a = +4°) 

 L. = E. hievopinea (d = "870, a = - 47°). ' Ca. = E. capiiellata (d = •917, a = + 4°) 

 VV.= E. Wllkinsoniana (d - "894,0 = -24°). Ma. = E. man-<yrh ynrha (d = -929, a = - 1°) 



In Fip-. 1, the curves are giren for severiil of the typical stringybark 

 oils, and, although the data recorded by Baker and Smith are some- 

 what scanty for this purpose, the difference between each curve is 

 clearly to be seen, and corresponds to the characteristic composition 

 of eacli oil. 



These curves distinguish two classes of stringybarks, the one 

 including such species as E. hievo-pinea, etc., which yield oils com- 

 mencing to distil at about 156 dcg. C, and containing either dextro - 

 or laevo - pinene, and the second, which like E. Diacrorhjjnchd yields 

 oils containing phellandrene, but not pinene, and only beginning to 

 distil at a])ove 170 deg. C. 



Whereas some of the constituents can be directly determined by 

 chemical methods, others such as pinene can only be approximately 

 estimated bv a more or less reliable calculation from the physical 

 constants of the oil and its fractions. 



The method we adopted is as follows: — 



Fifty cubic centimetres of the oil are fractionally distilled in dupli- 

 cate, and the density, optical rotation and refractive index of each 

 fraction is observed. The lightest fraction is analysed for volatile 

 aldehydes by absorption with a sodimn bisulphite solution ; eucalyptol 



