In 1895 Bourchardat and Tardy§ carried out experiments with the hydrocarbon found occurring in small quantity in the oil of E. globulus, and arrived at the conclusion that it had the properties of the lævo-rotatory terebenthene found in French oil of turpentine, but with an almost equal opposite rotation. They gave its boiling point as 156-1570 C.; its density as 0.870 at 0° C. and 0.865 at 18° C., and its specific rotation at 150 C. as [a]D + 390 C. They gave Riban's determination|| for the specific rotation of lævo-rotatory terebenthene as - 40.3°. It appears, therefore, from the results obtained by these authors on this hydrocarbon from the oil of E. globulus, and those obtained in this research on the same hydrocarbon from the oil from E. dextropinea, that these dextro-rotatory pinenes obtainable from members of two distinct groups of Eucalypts are identical bodies, and that the dextrorotatory pinene from the whole Genus Eucalyptus is a physical isomeride of the lævo-rotatory pinene (terbenthene) obtained from French oil of turpentine, and also of the lævo-rotatory pinene of the Eucalypts, although this lævo form has, as far as observed, a higher specific rotation.

* Compt. Rend., 1870, 687, and Journ. de Pharm. et de Chemie, 1870, xii, 201.

† Ber. 7, 63, 1429.

‡Ann. 246, 265-284. Abst. Chem. Soc, 1888, 54, 1205.

§ Compt. Rend., 1895, 120, 1417-1420.

|| Compt. Rend , 78, 788; 79, 314.

Although it had been assumed that pinenes having right and left rotations were probably present in Eucalyptus oils, yet no proof had previously been forthcoming that this was so. The isolation of the corresponding lævo-rotatory pinene from the oil of E. 1evopinea, E. Wilkinsoniana, and other species shows conclusively that such is the case, and that we have existing in the oils of the Eucalypts two pinenes, one of which is the physical isomeride of the other. In this respect the oils of the Eucalypts differ from those of the Angophoras.

The two species of Eucalypts here selected, from which these highly rotatory pinenes were obtained, are members of a different group from that to which E. globulus, E. Bridgesiana, etc, belong. The study of the oils of the "Stringy bark" group has been of great assistance in helping to extend the knowledge of the constituents of the oils of the Genus.

Cineol is present in very small amount in the oils of these two species, being rather more pronounced in that of E. lævopinea, and it was only possible to detect it with certainty in the portion of the oil distilling at the right temperature. It is not thought that at any time of the year will cineol be found to be much more in evidence, and a determination for cineol by the resorcinol method in the oil of E. dextropinea only gave a return of 6 per cent. in the crude oil.

The Currawang Creek sample of E. dextropinea gave 63 per cent., boiling between 156 and 162 ° C, and 25 per cent. more distilling between 162 and 1720 C. The oil from the Barber's Creek sample, under exactly the same conditions, gave 62 per cent., boiling between 156 and 162° C, and 25 per cent. more between 162 and 1720 C. Further investigation showed these two oils to be practically identical, although the Barber's Creek sample was rather more highly dextro-rotatory than that from Currawang Creek, but differences of this character might be expected, because experiments have shown that oils obtained from trees of the same species growing together under exactly similar conditions, have not the same rotations, but differ at times to the extent of a few degrees. Constancy in optical rotation is not observed with Eucalyptus oils, although the variation as a rule only extends to a few degrees.

The oil from the Rylstone Eucalypt, rectified under exactly similar conditions, gave 60 per cent., distilling between 157 and 1640 C, and 28 per cent. more between 164 and 1720 C. so that the temperature required to distil the lævo-rotatory pinene was slightly higher than that necessary to distil the dextro-rotatory form. The higher boiling point 1 was, however, traceable to the rather larger amount of cineol in the oil of E. lævopinea.

The dextro-rotatory pinene. - The crude oil of E. dextropinea, from Currawang Creek, gave the following results: -

On rectification, 2 per cent. came over below 1560 C, this portion contained a little acid water and a small quantity of volatile aldehydes.

Continuing the distillation: -

The crude oil from E. dextropinea, from Barber's Creek, gave the following results: -

On rectification 2 per cent. came over below 156° C.

Continuing the distillation: -

It is thus apparent that the two samples might be considered as identical oils, only varying to the extent usually found with those of the same species of Eucalyptus at the same time of the year. Further investigation was, therefore, continued on the oil from the Barber's Creek sample alone. On redistilling the portion boiling between 156° and 162° C. the following results were obtained: -

The third and final rectification, taking the portion distilling between 156-158° C, gave 50 per cent. boiling between 156 and 157° C. This fraction gave the following results: -

By taking the specific gravity obtained at 18° C, the specific rotation was [a]D 4- 41-2°. The refractive index at 20° C. for a specially prepared sample was 1.4661.

A sample of commercial dextro-rotatory oil of turpentine, rectified in the same apparatus, under exactly similar conditions, and using the same corrections, gave 35 per cent. distilling between 156 and 157° C. This fraction had specific gravity at 20° C. = 0.8624, and a specific rotation [a]D + 13.8°.