420 



The diterpene was readih' prepared in a perfectly pure condition, so that 

 it was possible to determine satisfactorily its composition and ph3^sical properties. 

 This \vell crystallised body is thus one of the \ery few members of this class of plant 

 substances, which can be prepared from natural sources in a perfectly pure con- 

 dition. Our sample of the oil was obtained by steam distillation, and contained 

 about 3 per cent, of the solid diterpene. The oil was almost free from compounds 

 containing oxygen, and esters, alcohols, aldehydes, and similar bodies were practi- 

 cally absent, only a very small amount (about i per cent.) of an alcohol being 

 determined bv acetylating the oil. The higher boiling lic|uid portion showed no 

 tendency to resinify, so that when the semi-solid crystalline mass, which con- 

 tained the diterpene, was spread upon porous plates for a few days, the whole of 

 the liquid portions were absorbed, the diterpene remaining in a perfectly white, 

 and even at this stage, almost pure condition. It was little soluble in cold alcohol, 

 but more readily in hot alcohol, and dissolved easily in chloroform, ether, 

 petroleum ether, and benzene. The best method for purification, after the first 

 separation from alcohol, was to chssolve it in chloroform and precipitate by the 

 addition of alcohol. If the chloroform was in excess, so that on the addition of 

 alcohol no precipitate was formed, then on slow evaporation, crystals readily 

 separated. These crj'stals were microscopic needles, but were not well defined. 

 \\'hen onl}- a small amount of chloroform was used as solvent, then on addition 

 of the alcohol the solid substance at once crystallised out. When this was dried 

 on the slab it had more of a platy structure, was pure white, of a nacreous lustre, 

 and was practically without odour. It was dextro-rotatory, and the determina- 

 tion of the specific rotation was made with both benzene and chloroform, the 

 specific rotation, [«]„= -|- i6-o6°, being identical with both solvents. Its ready 

 solubility in benzene enabled the molecular weight to be determined by the 

 cryoscopic method, and this, together with the results of the analyses, showed it 

 to have the formula, Co,, H;,.,. Its melting point was 95° C. (cor.), and it did not 

 matter what the solvent had been. The fused substance also melted again at the 

 same temperature. It is perhaps a concidence that the melting point of this 

 solid diterpene is practicallv double that of the melting point of camphene, the 

 solid C,oH,„ terpenc, and which has of course half its molecular weight. 



Although the diterpene crystallised so readily, yet it did not sublime, 

 and it was not readily attacked by either dilute nitric or sulphuric acids, but was 

 acted upon by the concentrated acids. The ordinary potassium dichromate 

 oxidising mixture scarcely attacked it, but it was readily oxidised by chromic 

 acid when dissolved in acetic acid. Strong nitric acid slowly dissolved the 

 crystals in the cold to a yellow sohition, and with rontinued evolution of a 

 small amount of brown fumes. If the action was not allowed to continue too 

 long, a yellow nitro-compound was separated on the addition of water. This 

 gave a marked reaction for nitrogen, and melted to a thick dark-coloured li(|uid 

 at about 115-120° C, but the melting point was not sharp, and it softened 



