318 KEPOKT— 1873. 



in various cases, some light might be thrown on this question ; but unfortu- 

 nately this appears to be impracticable. 



With a view to obtaining another variety of cymciic for comparison with 

 the above, some experiments were made with citronella-oil, which was found 

 by Gladstone to contain a substance boiling at 199°-20o°, and agreeing in 

 composition with the formula Cjj,HjgO ; it was expected that this body would 

 behave like myristicol on treatment with zinc chloride or phosphorus penta- 

 chloride. On examining about GOO grams of pure oil of citronella obtained 

 from Messrs. Piesse and Lubin, however, no quantity of this constituent 

 could be isolated ; the great majority of the oil is made up of a substance 

 which agrees tolerably accurately with the formula Cj^Hj^O, and boils at near 

 210° ; the action of heat on this substance, however, alters it, converting it 

 into substances of higher boiling-point, and finally into a resin not volatile at 

 the limits of the mercurial thermometer : this resin appears to be a polymeride 

 of Cj^HjgO minus the elements of a portion of water. 



The examination of the citronella products is not yet complete, and the 

 account of them is therefore deferred untU next year ; the following points, 

 however, appear to be made out. 



By the action of zinc chloride the body C,uH|^0 splits up partially into 

 water and a hydrocarbon, or mixture of hydrocarbons, boiling between 170° 

 and 180°, and approximating to the formula Cj^H^^ ; so that apparently the 

 action is mainly 



C.„H„0=H,0+C,„H,,. 



A large quantity of a resinous body which approximates to the composition 

 (C,„H|^,)„ is simultaneously formed. 



By the additiim of two equivalents of bromine to the body C,„1I,^0 heat is 

 developed; on distillation of the resulting brominated liquid (which does not 

 crystallize on standing) it breaks up into water, hydrobromic acid, and a 

 hydrocarbon which appears to bo cymene, formed thus — 



C'A,0 + Br, = C,„H,„Br,0, 

 C\„H,,Br,0=H,0+2HBr+C,„H,,. 



It is proposed to contiuue these researches in whatever direction may seem 

 most promising for the fulfilment of the object in view, viz. the obtaining of 

 additional knowledge on the subject of isomerism in tho terpene series and 

 their derivatives. The strong tendency of most of these substances to poly- 

 merize and alter, forming resinous uon-volatile masses, renders working on this 

 subject somewhat difficult, large quantities of raw material being I'equisite in 

 order to obtain sufficient of any given derivative to submit it to careful study. 

 From wliat has been already done, together with the results obtained by 

 Baeyer, Oppenheim, Kekuld, Barbier, &c., it appears that the constituents of 

 the " Essential Oils " (wliich are most frequently either terpenes or deriva- 

 tives from terpenes) are intimately connected with the benzene series of 

 hydrocarbons ; it is proposed to study these connexions more minutely 

 wherever practicable. 



Appendix. 



Further experiments, made since the above Report was written, have con- 

 firmed the formula C,^,H,^0 as that of the main constituent of the sample of 

 citroneUa-oil examined ; phosjihorus sulphide acts on this substance just as 

 zinc chloride, producing a terpene boiling at 1G0°-1G5°, and polymerides of 

 higher boiling-point. The cymene obtained by the actioii of bromine appears 



