(H.I). & J.H.M., Proc. Linn. Soc, N.S.W., 1899, p. 616, P1. L.) Black Peppermint of New England, N.S.W.

Systematic. - A medium-sized tree, with a dark straight bark, thinner than that of E. Bridgesiana, R.T.B., semi-persistent on the trunk, more or less ribbony on the boughs, and deciduous on the ultimate branchlets. Abnormal leaves glaucous, often 3 inches long and 2 1/2 inches broad; orbicular to cordate, often stem clasping. Normal leaves lanceolate, and, when fully mature, 3 to 4 inches long and 1/2 inch wide on the average ; veins strongly marked, pinnate, and anastomising, the intramarginal vein at some distance from the edge. Buds from two or three to six in an umbel; on a flattened stalk of about 1/4 inch; the stalklets less flattened and less than half the length of the stalks. The buds glaucous and often pink or purplish, ovoid, the top of the operculum somewhat pointed; the operculum usually about the same size as the calyx tube. The flowers are usually borne in great profusion.

Fruit. - Usually glaucous, but sometimes entirely glabrous ; hemispherical with a well-defined, more or less domed rim; the three or four valves sometimes well exserted; 2 1/2 lines long, 2 to 3 lines in diameter.

Habitat. - New England district, New South Wales.

ESSENTIAL OIL. - Leaves and terminal branchlets for distillation were first forwarded to the Museum in Sept., 1899, by Mr. J. F. Campbell from Walcha, N.S.W. The yield of oil was 0.5 per cent. Later, in the years 1907 and 1910, a somewhat extensive investigation was undertaken with the oils of this species growing in the New England District, N.S.W., the results of which were published by us in the Proc. Roy. Soc, N.S.W., Nov., 1911. Material was obtained for distillation from the following localities:-Black Mountain, near Guyra, in August, 1907; Uralla, in July, 1907; Armidale (where it is known as " Red Peppermint "), in June, 1907; and from Tenterfield, in January, 1910. The material from which the original data were obtained, and published in the first edition of this work, was collected in September, 1899, at the time of the year when the lower boiling terpenes might be expected to be present in greatest amount. The crude oils of all the samples were red in colour, due to the action of the phenols on the iron removed from the still; inclined to be viscid, owing to the excess of sesquiterpene, and had a terpene odour not at all distinctive. Light did not pass well with the crude oils until the colour had been removed. The principal constituents in the oil were dextro-rotatory pinene, and the sesquiterpene, of which latter constituent more than half the oil consisted. Cineol was present in minute quantity only, at any time of the year. The peppermint ketone (piperitone) does not appear to occur in the oil of this species, so that the vernacular name "Peppermint" cannot be due to the odour given by the leaves, but probably to the appearance of the bark, and of the tree generally. The chemistry of the exudation also shows this tree not to belong to the " Peppermint " group.

The following table gives the general results obtained with the crude oils of this species from four localities given above. The yields of oil were from leaves and terminal branchlets collected as for commercial oil distillation.

On rectifying the crude oil of the Tenterheld sample, 1 per cent. distilled below 1590 C. (corr.). Between 159-170°, 10 per cent. distilled; between 170-245°, 9 per cent. came over ; and between 245-273°, 76 per cent.; over 50 per cent. distilling between 26-5-273°. These fractions gave the following results: -

The light passed the third fraction very well when diluted with chloroform. The two first fractions were again distilled, when 9 per cent., calculated on the original oil, came over between 156-1570 C. This fraction had specific gravity at 150 = 0.8631; rotation aD + 31.6°; refractive index at 200 = 1.4668, and was almost pure pinene. The nitrosochloride melted at 103-40. The oil of this species is one of the best from which to obtain the sesquiterpene.

The fractions distilling below 170°, as first obtained, had the following specific gravities and rotations :-

The crude oil of the original sample from Walcha had specific gravity at 15° C. = 0.907; rotation aD + 14.5°; refractive index at 20° = 1.4843, and was insoluble in 10 volumes 80 per cent. alcohol. The saponification number for the esters and free acid was 5.1.

On rectification 38 per cent. of the oil distilled below 1670, and 43 per cent. above 2500 C. The specific gravity of the first fraction was 0.8670 at 15°, and of the other 0.9310. The optical rotation of the first fraction was aD + 33.07°.

The Walcha sample was stored in the dark, and in December, 1919, was again analysed. Very little alteration had taken place during the twenty years the oil had been kept. On distillation 49 per cent. came over below 190° C, which was separated into two fractions, 155-170° and 170-190°. The crude oil and the two fractions gave the following results: -

The cineol was determined by the resorcmol method in the portion distilling below 190° C. When calculated for the crude oil the result was 6 per cent.

The Sesquiterpene. - The oil of this Eucalyptus species is one of the best from which to prepare the sesquiterpene in as pure a condition as possible.

300 c.c. of the crude oil were distilled at 10 millimetres pressure. The following fractions were obtained :-

The second fraction was repeatedly redistilled at the same pressure, finally over sodium, until a fraction representing 20 per cent. of the crude oil was obtained, boiling at 124-1250 C. This had specific gravity at 150 C. = 0.9222 ; rotation aD + 47° ; and refractive index at 20° = 1.4964. These are, therefore, the constants for the sesquiterpene aromadendrene. (See also the article dealing with this substance.)

The sesquiterpene alcohol boiling above 1400 C. at 10 millimetres was laevo-rotatory. The residue had saponification number after acetylation 115.3, and was laevo-rotatory aD - 15-4°. The refractive index was 1.5124.