ON THE CONSTITUTION ETC. OF ESSENTIAL OILS. 315 



The formula Cj^H^^ requires- carbon = 88-23, hj'drogen = 11-77; wliilo 

 Cj(,Hj^ requires carbon = 89-55, hydrogen 10-45. 



Prom these numbers it is inferred that nutmeg-oil contains at least two 

 terpenes, one boiling at about 164°, the other at about 17G°, or 12° liigher, 

 the former predominating, and the " myristicene " of Gladstone, boiling at 

 1G7°, being a mixture of the two. The lowest of these two terpenes does 

 not appear to be mixed with any great quantity of a lower hydrocarbon, 

 such as Cj„H,^, but is not necessarily free from such admixture ; for quantities 

 of 9 and even 14 per cent, of Cj^^Hj^ in the mixture produce very little alter- 

 ation in the calculated numbers, requiring respectively = 88-36, H = 11-64, 

 and 0=88-42, H = ll-58. The higher hydrocarbon, however, contains cer- 

 tainly a considerable percentage of 0,^,11,^ (probably cymcne, which boils at 

 about 176°) ; for the observed numbers are uniformly short of the hydrogen 

 percentage required for Oj(,Hj^, and coincide precisely with those that would 

 be furnished by a mixture containing 20 or even 25 per cent, of cymene, 

 such mixtures requiring respectively 0=88-49, H = 11-51, and = 88-56, 

 H= 11-44. 



As shown in section 4, the 163°-164° fraction yielded by careful oxidation 

 by nitric acid 13-2 per cent, of a mixture of toluic and terephthalic acid, in the 

 proportion of 1 of the former to 4 of the latter ; if it be assumed that these 

 acids arose solely from the oxidation of cymene, Oj^H,^, present in the hydro- 

 carbon employed, this would indicate the presence of at least 11-1 per cent, 

 of cymene in the hydrocarbon, a quantity which, as just shown, is less than 

 that which might be present without being appreciable by ordinary analysis. 

 The quantity of toluic + terephthalic acids yielded by the fractions boiling at 

 175°-177° has not yet been accurately determined, but it appears to be 

 greater than that obtained from the lower fraction. The general conclusion 

 drawn from aU this is, that it is not at all improbable that the terephthalic 

 acid produced by the oxidation of various terpenes, such as oils of turpentine, 

 lemons, &c., is derived, not from the C^JI^^ present in tlie liiidrocarhon used, 

 hut from tlie admixture of a certain amount of cymene in the substance em- 

 ployed, and that, in consequence, the supposed identity of such hydrocarbons 

 and their relations to benzene are by no means proven — a conclusion 

 strengthened by the results obtained \ni\\ the orange-tcrpenc, hesperideno, 

 from which no terephthalic acid at all is derivable by oxidation, although 

 otherwise its oxidation-products very much resemble those of the other 

 terpenes. 



2. Oil of Orange-peel (Portugal of commerce). — On slow distillation of this 

 oil the majority came over below lbO° ; a few drops of oxidized product came 

 over at 240°-250°, agreeing with the formula 0,„H„,O3=40,„Hj„-t-O, ; and a 

 small quantity, 2-S per cent., of a non-volatile inodorous resin was left behind, 

 agreeing mth the formula 0^(,H3^O^ = 20j„TTj,-f-O3. 



Like the nutmeg-oil, there is present a substance boiling at 210°-220°, 

 giving numbers agreeing nearly with the formula Cj^Hj^O, and converted by 

 heat into an isomeric non-volatile resin : the sole ditf'ercnce observed between 

 this body and the uutraeg-myristicol is in smeU, the one smcUing of nutmeg 

 and the other of orange-peel ; the smaU proportions in which it exists in 

 orange-oil has prevented anj^ minute examination of it as yet. 



Fully 95 per cent, of the oil is a hydrocarbon which, after many distilla- 

 tions over sodium, boils constantly at 178° (corrected) ; Gladstone tinds 

 that hespcridene boils at 174°. 



This is a terpene, as it gave on analysis carbon=8S-17, hjdrogen= 12-06, 

 while OjjjHjj. requires 0=88-23, H=ll-77. 



