EUCALYPTUS. 247 



observers remark : — " In our previous paper we have alluded 

 to a saiople of ' pure eucalyptol ' which we stated to have no 

 rotation. This observation we find to be not strictly accurate. A 

 column of 100 m. m. only was examined, and the deviation, when 

 compared with those of other samples of eucalyptol, seemed to 

 justify this opinion. On examination some months later, using a 

 220 m. m. tube, it was found to deviate the ray + 16', equal to + 

 7' for the 100 m. m. tube. Our eucalyptol has therefore a smaller 

 rotation, and in an opposite direction to the sample we had 

 regarded as pure. 



" The melting point of the crystals was 0° to 0^-5 C, and the 

 solidifying point of the liquid —1^ to O^C. The sp. gr. was taken 

 at the temperature of 4'^"*C., 10°-5 C, 25^0. and lOO^C, the 

 comparison being made in each case with water at the same 

 temperature. At 4^0., the gravity was '9342 ; at lO^C, -9139 ; at 

 15°-o, -9275 ; at 25^ -9216; at 100°, '8910. 



" In the mention of this substance in Watt's Dictionary, 2 ed., 

 ii., p. 536, it is indicated that eucalyptol is probably identical with 

 cineol, a remark that most recent workers endorse, but the sp. gr. 

 of cineol is stated to be -927 at 16^0., as against '923 for eucalyptol. 

 Our eucalyptol -9275 thus confirms the statement that eucalyptol 

 is identical with cineol."* 



(Various figures have been assigned as to the sp. gr. of eucalyptol. 

 Jahn gives 0^923 at 16° C, and 0-940 at 0° C.f; Merck gives as 

 properties of " Eucalyptol puriss," boiling point 170°-173° C. ; 

 sp. gr. 910-920 at 15° C.J ; Schimmel§ says : 0-930 at 15° C. 

 Constant boiling point 176°-177° C). 



" Some experiments were made to ascertain how far the amount 

 of eucalyptol that crystallised out could be taken as a measure 

 of that contained in the oil submitted to cooling. For this purpose 

 the eucalyptol was mixed in various proportions with substances 

 regarded as containing no eucalyptol, and the mixture submitted 

 to freezing. The diluents chosen were (a) the fraction of 

 K amygdalina coming over above 177° C, and (h) absolute alcohol. 



* Pharm. Journ. [3], xxiii,, p. 205. 

 t Ibid., XV., p. 615. 

 t Ibid, xiv., p. 778. 

 § Bericht., April, 1890. 



