The ascending steam, finding its way among the chips, carries all the camphor with it, and on condensation in the cooler H, the camphor is deposited, and removed at suitable intervals.
To obtain the essential oils from flowers, plants, or seeds, the oleiferoul material is placed in an iron, copper, or glass still, of 1-1000 gal. capacity, and is covered with water; superposed is a dome-shaped Lid, terminating in a coil of pipe, placed in a vessel of cold water, and protruding therefrom with a tap at the end. On boiling the contents of the still, the essential oil passes over with the steam, and is condensed with it in the receiver; the oil and water separate on standing. A great improvement, introduced by Drew, Heywood, and Barron, is the use of a steam-jacketed still, as shown in Fig. 107. Steam is supplied from a boiler by the pipe a into the jacket J; within the head of the still, is fixed a "rouser" c, a double-brunched stirrer curved to the form of the pan, and having a chain attached and made to drag over the bottom, the whole being set in motion by means of the handle d. The still is charged, and nearly filled with water; the head is then bolted on, steam is admitted into the jacket, the contents are well stirred, and Boon the oil and steam are carried up the pipe e, condensed In the refrigerator /, and let out at g into the receiver 4. Here the oil and water separate, and escape by different taps.
In the illustration, it Is supposed that the oil obtained is heavier than water; It will then sink, and be drawn oat by the lower tap i, and, as soon as the water reaches the level of the upper tap k, it will flow into the siphon-funnel I, and thence into the still. Thus the same water is repeatedly used in the still. The pipe m conveys cold water into the refrigerator f; the water escapes as it becomes hot by the pipe n. When the oil distilled is lighter than water, the taps i k exchange duties. Before commencing operations, the siphon I is filled with water to prevent the escape of vapour.
An apparatus recently constructed by Rigand and Dus-surt is arranged so that dry steam enters directly among the matters to be distilled, and the temperature is always maintained at a high point. This is shown in Fig. 10S. It is claimed to yield a larger and superior product, and to prevent all chance of creating an em-pyreumatic colour, such as sometimes happens with other forms.
Distillation as n means of obtaining essential oils is worthy of every consideration. Generally it should be effected by steam; but there are cases (bitter almonds, &o.) where contact with water is necessary for the production of the oil, while in others, open fire and steam are equally applicable, though the latter is superior. The water employed must be perfectly pure and neutral, though in some cases (sassafras, cloves, cinnamon, etc.) common salt is added to raise the boiling point. The receiver is always some form (there are many) of "Florentine receiver."
In some instances (anise, etc.) where the distillation-products are solidifiable at a low temperature, the condenser-worm needs to be warmed instead of cooled.