Extraction of Eucalyptus Oil in Australia

Eucalyptus oil can be distilled from the leaves without difficulty by a simple method of steam distillation, together with a satisfactory condensing arrangement, and this procedure alone is sufficient for the preparation of the crude product. In the still erected for our own use the steam was generated in a separate boiler, and passed into the digester in which the leaves were packed, the pressure of steam in the chamber not usually exceeding 10 pounds at any time. Condensation was assured, so that the total oil obtainable from the leaves of the species was secured. The material was carefully weighed before being placed in the digester, and the weight of the oil determined to the nearest half-ounce. The leaves and terminal branchlets were used in all instances as would be done if collected for commercial distillation.

A first consideration from the oil distillers' point of view is the water supply. In the mountain ranges where the "Peppermint" Eucalyptus species abound, water is fairly abundant, but in the "Mallee" country this is not so, and the question of water for distillation becomes of considerable importance, the annual rainfall over the "Mallee" country being between 10 and 20 inches. Fortunately the water-holding capacity of the ground in the "Mallee" country is very good, so that it is not difficult to store the rain water by the erection of dams. This method of conserving the water in quantity is shown in the accompanying photograph (Plate cv), which represents the Shire Dam at Buddigower, near Wyalong, New South Wales. The photograph was taken towards the end of 1919, during the very severe drought of that year, and at the time when most of the smaller dams had dried up.

Plate CV.

The Buddigower Dam. Near Wyalong New South Wales.

The larger Eucalyptus oil distilleries in the "Mallee" country in Victoria have provided themselves with an abundant supply of water by similar methods.

As Eucalyptus oil is so easily distilled, and the leaf material not difficult to collect, it is only natural that very crude apparatus is sometimes employed, although with the more advanced distilleries, quite expensive and up-to-date steam-distilling plants are in operation. The consideration of the erection of a permanent plant of large capacity is, of course, a matter of ways and means, depending also on the available supply of leaf.

Eucalyptus species mostly grow intermixed, and it is only in rare instances that a particular species is found predominating over an area of country to any great extent, so that if energetically worked for oil production the species may soon be cut out in close proximity to a permanent plant of large dimension. For this and other reasons, it has, in certain cases, been considered advantageous to erect mobile distilling plants, which are removable without difficulty to fresh localities,

Most Eucalypts are very tenacious of life, and new growth soon springs from the stumps of the trees cut down, so that it is only a matter of a comparatively short period before fresh material is again available, and usually in greater abundance than was the case originally. Instances of this rapid reproduction may be seen from the illustrations already given in this work.

We have previously shown that the oil obtainable from this young growth is of the same character as that from the mature leaves, so that little difference in the quality of the oil will be observed. If then the areas be sufficiently extensive, the supply of material for oil distillation will be continuous, and a permanent plant an advantage if security of occupation is assured. Considerations respecting the continuity of supply of leaf material and of cultivation have been dealt with in a previous article.