oo7 



therefore, the conditions were abnormal. We think, ho\ve\'er, that there has been 

 no alteration in the formation of the chemical constituents to what maintained 

 in the uninjured trees. \Mien the bark of A. Bidwilli was cut through there was 

 an exudation at once from the cut cells or canals, both from above and below. 

 The downward flo\\- soon ceased, but the upward flow continued for months, the 

 exuded material being collected each week. The material forced up months after 

 the injury was identical in composition with that \\-hich exuded when the trees 

 were first injured. 



Although many members of the terpene series have been converted into 

 hydrocarbons of the formula Cj„H.,,„ x'et, it is probable that none have been isolated 

 from essential oils, for the reasons above stated. 



The natural hydrocarbon C, ,H,,,, as obtained from this latex, is a very 

 limpid, colourless, volatile liquid, with an odour somewhat reminding of menthene, 

 but more pleasant and delicate, and not so strong. It had specific gravit}^ at 

 xf° C. =0-7927; refractive index at the same temperature ;iD= 1-4437; it 

 boiled at 155° C. (cor.), and was inacti^•e to light. Bromine acted slowlv upon it 

 h\ substitution ; nitric acid and sulphuric acid did not act upon it in the cold, 

 but warm nitric acid oxidised it. A dilute solution of potassium permanganate 

 acted ver}' slowly upon it, but the products formed could not be determined for 

 want of material. 



Wallach and Berkenheim (Ann. Chem. 268, 225) prepared a hydrocarbon, 

 tetra-hydropinene Cj„H.,,„ b}' the hydration of pinene hydrochloride. It boiled 

 at 162° C, had specific gravit}- 0-795, and a refractive index WD = 1-43701 at 20° C. 



\\'allach Ann. Chem. 284, 326) prepared tetra-hydrofenchene Cj,.H.„„ 

 which in chemical behaviour resemb.ed- tetrahydropinene ; it boiled at 160-165° C. ; 

 had specific gravity 0-7945; and index of refraction wd — 1-4370 at 22° C. 



\\'agner ^Ber. 27, 1638^! prepared a hydrocarbon, Ci„H,,, by the action of 

 sulphuric acid on menthol. It boiled at i68-i6g°, and had specific gravity o-8o8S 

 at 0° C. - ■ 



Knoevenagel and \\'iedermann (Ann. Chem. 297, i6g^ prepared i : 3 meth}^- 

 isopropvlcvclohexane by reducing the iodide of symmetrical menthol. It boiled 

 at 167-168°; had specific gravity 0-8033 at 14° C; and a refractive index «D = 

 1-44204. 



Similar products have been prepared synthetically by W. H. Perkin and 

 coadjutors, the results of which are published in the Journ. Chem. Soc. for the 

 year 1905. The orthomenthane boiled at 171° C. ; the para form at 169° C. 



From the above it is seen that the natural hydrocarbon, C^^H,,,, from this 

 latex, boils at a lower temperature than the artificially prepared compounds from 

 Y 



