This section is from the book "A Research On The Eucalypts Especially In Regard To Their Essential Oils", by Richard T. Baker, Henry G. Smith. Also available from Amazon: A Research On The Eucalypts And Their Essential Oils.
(Schlecht. in Linnea, xx, 655.) Murray Red Gum.
Systematic. - A tall tree with a whitish, smooth, persistent bark. Leaves lanceolate, falcate, up to 9 inches long and 1 inch wide, of medium thickness, of equal colour on both sides; venation distinct, lateral veins oblique, spreading, numerous, intramarginal vein removed from the edge. Peduncles axillary, terete or flattened, about 6 lines long, with an umbel of less than a dozen flowers; pedicel almost filiform, and about 4 to 6 lines long, or short and thick. Calyx tube uniformly hemispherical, from 1 1/2 to 3 lines in diameter; operculum variable in shape, sometimes larger than the calyx, and then it is conical and obtuse, but the most common form is hemispherical, surmounted with a very prominent beak.
Fruit. - On a slender pedicel, hemispherical, and consistently so; rim slightly variable in convexity; valves exserted, prominent; 2 to 4 lines in diameter.
There can be no mistaking this fruit, as it preserves its one form throughout its wide geographical distribution, and wherever planted in other parts of the world it is one of the easiest fruits of the Genus to recognise,
Habitat. - Banks of the Murray, Darling, Lachlan, and Murrum-bidgee Rivers and tributaries, and old filled-in watercourses. It is known as "Murray Red Gum" throughout its geographical range.
REMARKS. This Eucalyptus, commonly known as "Murray Red Gum," is the most widely distributed species of the Genus, as it occurs on the banks of almost all the rivers of the interior of the continent. In the State of New South Wales, however, there appear to be two varieties based on the chemical constituents of the oil. Morphologically they seem to be alike, but after our experience with E. stricta and E. apiculata no doubt some distinguishing form or characters will be found that at present evade detection. The type is here regarded as those trees found on the Murray, Lachlan, and Murrumbidgee Rivers; whilst those growin in more northern localities, such as Nyngan and Broken Hill, are placed as a variety under the name of E. rostrata var. borealis.
ESSENTIAL OIL. - Leaves and terminal branchlets for distillation were received from Anbury, N.S.W., in September, 1899. The yield of oil was 0.14 per cent. The crude oil was red in colour, while that of the rectified oil was yellowish in tint, as is usual with Eucalyptus oils belonging to this group. The oil contained a small amount of phellandrene and some cymene. A small quantity of cineol was present, but not more than 8 to 10 per cent. in the crude oil. The presence of aromadendral was well marked, and it was to the occurrence of this constituent in some quantity that the high lævo-rotation of the oil was due.
The crude oil had specific gravity at 150 C. = 0.904; rotation aD - 11.8°; refractive index at 200 = 1.4839, and was soluble in 2 volumes 80 per cent, alcohol. The saponification number for the esters and free acid was 10.6.
On rectification 2 per cent. distilled below 1730 C. (corr.). This portion consisted principally of volatile aldehydes with a little acid water. Between 173-189°, 52 per cent. distilled; between 189-250°, 18 per cent. came over, and between 250-260°, 8 per cent. distilled. These fractions gave the following results: -
First fraction, sp. gr. at 150 C.
The higher rotation shown by the crude oil over that of the fraction distilling below 189°, was due to the presence of aromadendral in the higher boiling portions.
Material of this species for distillation was also received from Hay, N.S.W., in November, 1900. The yield of oil was 0.28 per cent. In colour, odour, and constituents this oil was similar to that of the same species from Albury, the difference in the time of year probably accounting for the increased yield. A slight increase in the amount of terpenes was shown by the slightly higher rotation, less specific gravity, and an increased amount distilling below 183° C.
Cineol, phellandrene, and aromadendral were all detected. The cineol, determined by the phosphoric acid method in the portion distilling below 183° C. (65 per cent.), was 19.6 per cent., or about 12 per cent, in the crude oil. The specific gravity of the crude oil = 0.8953, and the optical rotation aD - 14.5°.
Material of this species for distillation was also obtained from Condobolin, N.S.W., in March, 1901. In appearance, odour, and constituents the oil differed in no respect from the Albury and Hay samples.
The above samples were mixed and stored in the dark, and in October, 1919, nineteen years afterwards, the oil was again analysed. But little alteration had taken place during that period, although perhaps a slight increase in cineol content had taken place, but the present determination was made by the resorcinol method in the fractionated portion, and then only indicated 20 per cent. in the ciude oil.
On rectification 72 per cent, distilled below 1900 C. The crude oil and the fraction gave the following results: -
Crude oil, sp. gr. at 15o C.
0.9040; iotation aD 140; refractive index at 200 = 1.4830.
0.8847; rotation aD - 13.2°; refractive index at 20° = 1.4773.
The aromadendral was quite as pronounced as when the oils were freshly distilled.
Later, in June, 1911, leaves and terminal branchlets of this species for distillation were collected at the Kingscote end of Kangaroo Isand, South Australia.
The yield of oil from this material was 0.38 per cent. Cineol was present, but in small amount, and a small quantity of phellandrene was also detected; cymene was present in some quantity. The oil from this material gave results which were in close agreement with those published in the first edition of this work, and again recorded above.
The crude oil of the Kangaroo Island E. rostrata had specific gravity at 150 C. = 0.9047; rotation aD - 12.4°; refractive index at 200 = 1.4890, and was soluble in one volume 80 per cent, alcohol. The saponification number for the esters and free acid was 6.1.