The empirical formula obtained with the deposits of E. oleosa, E. populi-folia, and the undetermined species from Queensland, was C7HIOO in each case, but with those of E. punctata and E. occidentalis it was C8HI2O. Molecular weight determinations were carried out by the Landsberger boiling point method, using chloroform as solvent. The results were fairly uniform for material of this character, although the molecular weight was so high.

With the deposit from E. globulus the following was obtained: - 1.0416 gram, gave the figure 1.368 for ev as the mean of several readings, so that the molecular weight was 1979.

With that from E. occidentalis 1.1256 gram. gave the figure 1.492, molecular weight = 1960. With that from the undetermined species from Queensland: - 1.685 gram. gave the figure 2.2, molecular weight = 1992. Calculating from the empirical result with the deposit from the Queensland species, the molecular formula is CI26Hl8oOl8, and with that from E. occidentalis C128H192Ol6.

The specific gravity of the powder was 1.08. It also gave a saponification number 87, and an iodine value 105, although no absorption of bromine was shown in the chloroform solution.

The Comparative Constancy of the Oil Products from Individual Species of Eucalyptus.

This question may be considered as one of considerable importance to the distiller, particularly as Eucalyptus trees are so abundant in Australia, the greater portion of the natural vegetation of the country being composed of trees belonging to this genus.

The leaves of all the Eucalypts are evergreen, so that distillation can proceed throughout the year, but the oil is less in amount during the winter months. Although practically all the species contain an essential oil, yet, with many of them, the yield is very small indeed, and thus they are not profitable to work. (See table of yields in separate list.)

From a commercial point of view only a small percentage of the species can be utilised for oil production, the principal reasons for such limitation being (1) the constitution of the oil itself, and (2) the variation in the amounts of oil yielded by the several species.

The competition for trade among the distillers naturally causes those species which produce the greatest amount of oil per tank,* all else being equal, to be the most in demand, and consequently distillation from material growing naturally can only be carried on profitably in those portions of the country where the desired species abound. It has been this question of yield that, among the richer cineol-bearing oils, has caused E. globulus to recede in the world's markets from the position it once held, and in Australia to-day only a very small amount of oil is distilled from that species, the reason being that the yield is too small in amount for it to compete satisfactorily with the more profitable Eucalypts, such as E. polybractea, E. Australiana, E. cneorifolia, E. Smithii, etc, all of which furnish rich cineol oils, and give practically double the amount from the same weight of leaf material as from E. globulus. In the case of E. Australiana the yield is three times as great.

In view of the geographical distribution of the genus in Australia, with an area of 3,000,000 square miles, the number of distinct species is comparatively not great, but their oil products vary much in constitution among themselves, although comparatively constant for individual species.

The large amount of research which has been carried out during recent years on their oils, has demonstrated quite clearly that a particular Eucalyptus species will produce - from average material - an oil practically constant in composition and general characters,† and also give a fairly uniform yield, providing the material for distillation has been well selected and not too coarsely cut, or with too many branchlets.

* In some parts of Australia, New South Wales particularly, the standard upon which payment is made for cutting the leaf material, for calculating the contents of the digesters, and the statement of oil produced, is the 400-gallon square-iron tank, which holds approximately 800 pounds of material when filled for open firing.

† This matter is more fully considered in the early article dealing with the comparative constancy of specific characters of Eucalyptus species.

It has been this comparative constancy in the oils of identical species that has enabled the somewhat extensive trade in Eucalyptus oils - from naturally growing trees - to have been built up. Had it been otherwise there could hardly have been the desired constancy in the commercial article, nor could necessary standards for control have been arranged.

In order to illustrate this constancy in general characters from commercially collected material, the three tables below are given. The three species chosen are to be considered as types of groups, and all are now extensively utilised for oil production in New South Wales and Victoria.

The oils to which the figures refer were in these cases distilled for market, and forwarded to the Museum for investigation. There is not the slightest doubt, however, with the specimens tabulated, as to the botanical identity of the species from which the oils had been distilled. It will be noticed that the dates of the distillations extend over several years.

Space will only permit the tabulation of a few of the results, but they are sufficient to show the small range of variation in the chemical constituents likely to be observed in commercially distilled Eucalyptus oils when from one species only. Similar data from other species might equally well have been given, if thought necessary, as, for instance, with the perfumery oils E. Macarthuri, E. citriodora, etc, but a perusal of the results recorded in this work, under the several species, will supply abundant evidence of this comparative constancy of their oil products.