ON THE CONSTITUTION ETC. OF ESSENTIAL OILS. 317 



turpentine and oil of lemons, as well as other terpenes, as much stress has 

 been laid on the production of torephthalic acid and of cymene from these 

 hydrocarbons and their derivatives. 



The preceding experiments render it probable that the gradual resinizing 

 which occurs in terpenes on keeping arises from a spontaneous absorption of 

 oxygen and the consequent formation of the resinous polymerides (Cj„H,|,0)„. 



On treating the lowest hydrocarbon (b.-p. 163°-164°) obtained from nutmeg- 

 oil in the same way as the hesperidene, precisely the same results were ob- 

 tained, with the sole difference that a little terephthalic acid was also formed, 

 which was not tlie case with the orange-hydrocarbon. 



The cliromic liquor gave an acid distillate which contained acetic and 

 probably formic acids ; barium and silver acetates were analyzed, and the 

 apparently unattacked hydrocarbon left on distillation a few drops boiling at 

 upwards of 210°, and giving numbers on analysis identical with those given 

 by myristicol, by the oxidized constituent of orange-oil distilling at 210° to 

 230°, and by the similarly obtained oxidation-product of hesperidene just 

 described. Whether these four substances are identical or not cannot be de- 

 cided ; but the only difference noticeable between them was in the matter of 

 odour, each one being different from the others in this respect. 



The action of the chromic liquor on the higher boiling hydrocarbon of 

 nutmeg-oil has not yet been examined. 



4. Action of Nitric Acid on Nutmctj- and Orange-Terj^enes. — Schwanert 

 has shown (Ann.Ch. Pharm. cxxviii. 77) that where camphor and certain other 

 analogous substances are treated with nitric acid, there is produced, inter 

 alia, a non-crystalline acid, camjjhresinic acid, C^JI^fi^, which same acid also 

 x'csults when certain terpenes (e. g. Citronenol) are oxidized in the same way. 

 Kachler, however, has recently found (Ann. Ch. Pharm. clix. 281) that the 

 so-called camphresinic acid from camphor is a mixture, the principal con- 

 stituent of which is a crystaUizable acid, C,,Hj^O., to which he gives the 

 name camplioronic acid ; this is characterized by giving a sandy precipi- 

 tate on boiling a neutral solution of its ammonium salt with barium chlo- 

 ride, from which pi'ecipitate the acid is obtainable. 



On boiling hesperidene with from eight to ten times its volume of a mixture 

 of nitric acid diluted with its own bulk of water, a vigorous reaction sets in ; 

 red fumes and carbonic acid are copiously evolved, and after some time a brown 

 resinous substance is formed, which on further treatment with stronger acid 

 mostly becomes soluble : a small quantity of yellow resinous substance is, 

 however, left, much resembling the crude terephthalic acid obtained by the 

 similar treatment of nutmeg-oil ; this substance mostly dissolves in ammonia ; 

 but on digesting the dark solution with purified animal charcoal, the whole is 

 gradually absorbed, nitric acid finally giving no precipitate whatever in the 

 filtrate. A portion of the filtrate was precipitated before the total absorption 

 had taken place ; the trifling amount of flakes obtained gave numbers on 

 combustion very far from those required for terephthalic acid, and nearly the 

 same as those given by the yellow resinous substance before treatment with 

 ammonia and animal charcoal. 



Crude yellow resin gave carbon 46-1 Hydrogen. . 4-4 



Ditto partially purified by charcoal .... 47" 7 „ 4-G 



Terepththalic acid requires 57"8 „ 3-6 



From this it is inferred that the yellow resin was not terephthalic acid, and 

 that this body is not produced by the oxidation of hesperidene by nitric acid 

 (nor was it formed with chromic liquor as described in the last section). 



