The two reactions which serve to distinguish terpinene from other terpenes 

 are : (a) the crystallised nitrosite, C IO H I6 N 2 O 3 , melting at 155 C., which 

 is formed when the oil is treated with nitrous acid; and (6) the comparative 

 ease with which it is destroyed when treated in the cold with Beckmann's 

 chromic acid mixture ; this reagent under such conditions has little action upon 

 either pinene, limonene, or cineol. 



(a) THE FORMATION OF THE TERPINENE NITROSITE. 



A portion of the oil of E. mcgacarpa boiling between 170-190 C. was 

 mixed with an equal quantity of petroleum ether and an equal bulk 

 of a saturated solution of sodium nitrite added, and afterwards 

 sufficient glacial acetic acid to decompose the salt. The whole 

 was then allowed to stand on one side. After twenty-four to 

 thirty hours, crystals commenced to form, and increased consider- 

 ably in amount after two days. The crystals were separated, 

 pressed on porous plate to absorb the liquid products, and purified 

 from a mixture of alcohol and chloroform. The terpinene nitrosite 

 thus formed melted at 155 C. (corr.), and answered to the more 

 easily applied chemical reactions for this substance. 



Terpinene nitrosite, which is a much more stable substance than the 

 corresponding compound formed with phellandrene, has had the two following 

 formulae suggested for it, but no decision as to which is correct has yet been 

 arrived at. 



/N=0 XN-0 H 



C,,,H 6 / andC 10 H 15 <r 



\0 N = \0 N = 



(b) TREATMENT WITH BECKMANN'S REAGENT. 



A portion of the fraction boiling between 170-190 was repeatedly treated 

 in the cold with small quantities of Beckmann's chromic acid 

 mixture, until the formation of the brown precipitate was less 

 noticeable. The optical rotation of the fraction before treatment 

 was 35-6 to the left, due principally to the laevo-rotatory limonene. 

 After the first treatment, the optical rotation had increased to 36-4, 

 and after further action to 36-6. The substance removed was 

 evidently the inactive terpinene, the treatment apparently having 

 little action on the activity of the limonene. 



E. megacarpa, in the sequence of species, approaches more nearly 

 the earlier members of the genus, and this is also indicated by the principal 

 chemical constituent in the oil being pinene. The chief terpene in the oils of the 

 more recent species of the genus is phellandrene, so that a peculiarity is noticed- 

 here in that terpinene is found at that end of the genus more largely represented 

 in Western Australia, while the other closely agreeing terpene (phellandrene) 

 is a characteristic constituent in the oils of certain Eucalypts which occur more 

 abundantly in the eastern and south-eastern portion of the Continent, 

 the map in this connection, Plate n.) 



