421 



several degrees lower. On allowing the diterpene to remain in contact with the 

 nitric acid in the cold for some days a comparatively large amount of solid 

 acids was formed, but when it was warmed with strong nitric acid, energetic 

 action took place with evolution of abundant brown fumes. The principal 

 products of alteration were of an acid nature, were solid, and almost colourless ; 

 they were easily dissolved by alkalis, and precipitated again on acidifying, but 

 were not identiiied with any known acid. 



When warmed with concentrated sulphuric acid the diterpene was readily 

 dissolved, and on continued heating soon became of a very dark coffee colour, 

 with an indication of a greenish fluorescence. A sulphonic acid was apparently 

 formed, as on the addition of a little water a dark precipitate was obtained, but 

 this was almost entirely soluble in water. Aqueous alkalis had no action upon the 

 diterpene, nor was there any alteration when it was boiled with acetic anhydride 

 for a long time. When the diterpene was dissolved in acetic acid a solution of 

 bromine was not discoloured, nor was the colour removed at once when very 

 dilute bromine was added to a chloroform solution, or to a carbon-tetrachloride 

 solution. On the addition of more bromine, and allowing the solution to remain 

 some time, there was a slow evolution of hydrobromic acid, so that a substitution 

 product should eventually be obtained. It is evident, however, that the diter- 

 pene is a saturated compound. A dilute neutral solution of potassium perman- 

 ganate had no action upon it, and no change of colour took place even on heating, 

 nor was there any alteration when the solution was acidified. 



When more material shall have been obtained, further investigations will 

 be undertaken in order to determine the products of nitration, bromination, 

 oxidation, &c. 



The diterpene is a saturated substance, and in this respect differs from 

 both the accompanying pinene, and the sesquiterpene. As the formula of this 

 hydrocarbon is C,oH3.2 and the molecule saturated, it may, perhaps, be composed 

 of two molecules of a bicyclic terpene, the severing of a double bond in the 

 terpene molecule providing the connection. The bicyclic terpene in the oil, and 

 which answers to this requirement, is pinene, and it might be suggested, 

 therefore, that the diterpene may be composed of two molecules of pinene. The 

 generally accepted structure for pinene is 



C-CH, 



HC 



HaC 



^-CH2 



CH 



