AUSTRALIAN P1TT08P0RUM. 293 



and exjieriiiiented with the inner viscid portion, which is of 

 a homogeneous nature, and of approximately constant 

 composition. 



This soft interior portion was digested in ether, which 

 removed 6'0*09 per cent, of resin and oil, of which 6*29 per 

 cent, was a volatile oil. 



The residue was then treated with alcohol (-834 sp. gr.), 

 when 1-544 per cent, of resin was dissolved out — orange- 

 yellow in coloui" like that removed by ether. 



The remainder consisted of gum, which is almost insoluble 

 in water, even on boiUng, but which swells up very much in 

 that liquid. Its percentage was 37-29, of which -467 was 

 ash. 



Summary. 



Resin soluble in ether 53-8 



Volatile oil 6-29 



Resin soluble in alcohol but insoluble in ether 1 • 544 



Gum (metarabin) + truce of impurity 36' 823 



Ash -467 



Loss 1-076 



100-000 



The above analysis is to be taken as giving the true com- 

 position of the exudation oi Pittosporum. hicolor. 



The appearance of the gum-resin would indicate that it 

 contains a fixed oil, but such a substance is not present. If 

 gently pressed on paper, the gum-resin greases it in a 

 manner strongly resembling the stain of a fixed oil, but more 

 careful examination shows that this stain is owing to the 

 pasty solution of resin in essential oil about to be referred to. 



The oil associated with tlie resin evidently dissolves a por- 

 tion of the resin, and is in solution with it. It is driven off 

 with difficulty, and not entirely until Avater has been 

 l^reviously added. The resin does not darken much during 

 this process of driving off the essential oil. 



In order to obtain the essential oil, water is added to the 

 gum-resin to emulsify it. Tlie mixture is then rubbed up 

 and distilled at 110° C. by means of an air-bath. It is to this 

 volatile oil that the unpleasant odour of the gum-resin is due. 



The gum is difficultly soluble in caustic soda. The portion 

 dissolved is precipitated by alcohol, and answers to the tests 

 for arabin, showing the original gum to have been in the 

 form of metarabin. Acid solutions have no effect on the 

 gum-resin. 



