A low boiling ester, with a low refractive index, occurs in some quantity in the oil of E. Perriniana, is characteristic of this species whether growing in Tasmania or New South Wales, and is one of the distinguishing features between this species and E. Gunnii. Considerable work has been done on the oils of these species, distilled from material collected at both localities, and from this data, supported by botanical evidence, it is apparent that these two Eucalypts cannot be considered as identical species.

This ester is evidently a constant constituent in the oils of the members of a certain class of Eucalypts, although in most cases it occurs but in small amount. It is another instance of the peculiarity, so pronounced with chemical constituents in the genus Eucalyptus, by which is shown a progressive increase throughout a whole series of closely agreeing forms, the maximum being reached in one or more of them. Not only is this the case with the oils, but the various exudations and secretions also show a sequence, often running through the whole group, and this progression is sometimes remarkably complete.

Butaldehyde is a very common constituent in Eucalyptus oils, and is also one of the constituents which give to unrectified oils of this group a somewhat objectionable odour. The formation of the ester might perhaps be accounted for by a rearrangement in the aldehydic grouping. Normal butyric acid has already been identified as occurring in small quantity in several Eucalyptus oils, this acid probably being derived from the natural hydrolysis of the ester. A corresponding change takes place when the oil of E. Perriniana has been stored for a sufficiently long time,

The material of E. Perriniana from which the oil was distilled, was collected in September at Tingiringi Mountain, a locality in South-eastern New South Wales. The crude oil was rich in cineol, but phellandrene was not detected at this time of the year. The general characters agreed with those of the oil distilled from material of the same species collected at Strickland, in Tasmania.

The abnormally low refractive index of the lower boiling fractions led to the identification of this ester, because a refractive index, 1.4519 at 200 in ordinary fractions, had not previously been detected in Eucalyptus oils. The first notification of this ester was published by one of us in the Proc. Roy. Soc, N.S.W., December, 1914.

Experimental

The Acid. - The crude oil (200 c.c.) of E. Perriniana was distilled, and the portion which came over below 1900 C. boiled with aqueous potash under a reflex condenser for some hours. The aqueous portion was separated and distilled, but nothing came over below the boiling point of water, so that methyl, ethyl, and propyl alcohols were absent. The remainder was evaporated to dryness and the potassium salt decomposed by sulphuric acid and distilled until all the volatile acids had come over. The distillate had an odour of butyric acid strongly marked. The free acid was exactly neutralised with barium hydrate solution, evaporated to dryness and heated in the air-bath to 105 ° C. A molecular weight determination with the thus prepared barium salt gave the following: -

0.3592 gram, gave 0.2668 gram. BaSO4 = 74.28 per cent.

Barium butyrate forms, theoretically, 74.91 per cent. BaSO4, so that butyric was probably the only volatile acid present. The odour and other indications suggested the normal form for this acid, and the ethyl ester prepared with it gave the characteristic pineapple odour. To decide the point the calcium salt was prepared by decomposing the remainder of the barium salt with sulphuric acid, distilling over the volatile acid, exactly neutralising with freshly prepared and filtered lime water, using a trace of phenolphthalein as indicator, and evaporating to a small bulk on the water bath until a portion of the solid salt separated; this dissolved again, however, when the liquid cooled. The solution was transferred to a test-tube and again heated, when the precipitate again formed, but dissolved on cooling. This peculiarity of the calcium salt indicates that the acid of this ester is normal butyric.

The Alcohol. - The oil after saponification, was separated and distilled, when about 2 per cent. came over below 1500 C. A trace of cineol was present and most probably a trace of pinene also. This portion was carefully oxidised with K2Cr2O7 + H2SO4, heated to boiling, and allowed to stand for 24 hours. A volatile acid with the odour of butyric was readily detected. This was distilled over, exactly neutralised with barium hydrate solution, and evaporated to dryness and heated in the air oven. The barium salt thus obtained was identical in odour and gave reactions similar to that from the acid of the ester. Although the amount of the available salt was but small, yet, there was sufficient to enable a quantitative determination for molecular weight to be made.

0.0354 gram. gave 0.0264 gram. BaSO4 = 74.58 per cent. Barium butyrate gives 74.91 per cent. BaSO4.

As the ester is thus shown to be butyl-butyrate it might be assumed that both the alcohol and the acid are identical in form. Sufficient acid from the alcohol was not available with which to prepare the calcium salt, but its odour, as well as that of its ethyl ester, was identical with those prepared with the acid of the ester, and also corresponded with similar substances made with pure normal butyric acid.

The greater portion of the total esters in the oil of E. Perriniana appears to be the low boiling butyl-butyrate; this is shown from the saponification results with the freshly distilled oil. The saponification number for the crude oil was 52.6, representing 13.52 per cent. of an ester having a molecular weight 144. The saponification number for the portion distilling below 1900 C. (75 per cent.) was 57.2, representing 14.7 per cent. of ester in this fraction. The ester was not decomposed on direct distillation, as no free acid was detected in the lower boiling fractions.

It might be well in future analyses of Eucalyptus oils, distilled from trees belonging to this group, to determine the saponification number for the ester in the lower boiling fraction, particularly when the ester value for the crude oil is at all high.

On the completion of the work on the ester in the oil of E. Perriniana from New South Wales, one naturally returned to the oil of this species previously distilled from Tasmanian trees, the fractions of which had been preserved. The first fraction, representing 18 per cent. of the crude oil, distilling below 173° C, contained a little free acid formed by the natural hydrolysis of a portion of the ester. The saponification number for the ester and free acid in this fraction was 45.8. This result shows the ester in the oil of E. Perriniana of Tasmania to be a low boiling one, and also that the greater portion distilled over in the first fraction, as was the case with the oil of the New South Wales material.