sulphuric acid added to volatile oils will generate acetic ether if alcohol be present, which may be detected by its odor; and anilinered is insoluble in pure volatile oils, but colors these red in the presence of alcohol. Adulterations with rectified petroleum are often not easily detected, and may require a careful chemical examination; for it, as well as for the inferior volatile oils, the Pharmacopoeia prescribes appropriate tests under the head of the respective oils likely to be thus contaminated.

The usual method of obtaining volatile oils is by distillation. In some of the Asiatic countries, where the world's supply of a few volatile oils is still obtained, rather crude methods prevail even at the present time. Thus the plan is followed of using wooden cylindrical stills provided with a perforated diaphragm or false bottom, as shown in Fig. 204, on which the oil-yielding material is placed, water being put into the boiler on which the still rests and direct

Distillation of oil of cajuput in the Molucca Islands.

heat applied until the water boils, and the boiling continued as long as the distillate shows the presence of volatile oil. As shown in the illustration, the vapors are condensed in the cup-shaped condenser above the still, and flow from there into a suitable receiver, made of wood and lined with tin, whence the watery portion of the distillate flows back into the still, while the oil rises to the surface and is removed when a sufficient quantity has collected. In Fig. 205 may be seen the peculiar arrangement of a wooden still with tin condenser for the distillation of oil of cassia cinnamon. The still, as in the preceding case, is provided with a perforated bottom and rests upon an

FIG. 207.

denser and flows from there into earthenware receivers. Oil of cinnamon being heavier than water, the distillate is collected in a series of vessels in which the oil sinks to the bottom and the aqueous

iron boiler placed directly over the firepot of a brick furnace. The distillate collects in a gutter near the bottom of the cylindrical con

portion flows into another vessel, to be again used in a subsequent distillation. A still cruder apparatus, in use as recently as 1894, is shown in Fig. 206. It is used for the distillation of oil of cajuput, and consists of a wooden cask, a, into which are placed the leaves of the melaleuca plant and some water, and which is heated by means of a rudely constructed fireplace. The vapors are carried through the tin still-head b by means of a tube into the second cask c, which is kept supplied with cold water running in through the tube d, made of bamboo, where they are condensed and flow through a funnel-shaped device, made of cocoanut shell, into a bottle. The oil and water gradually separate, the oil rising to the surface and the water flowing into the tub e through a small hole near the bottom of the bottle.

Although the boiling-points of volatile oils are considerably above that of water, the oils pass over rapidly with the vapor of boiling water, and in the leading establishments in this country and Europe volatile oils are now distilled by passing steam under pressure into stills which contain the material on a series of perforated trays

extending across the inner body of the still; by this method compaction is avoided, the steam can readily penetrate every particle of the material, and a much finer quality of oil results, since prolonged contact with boiling water has a deleterious effect upon many oils. Fig. 207 represents the interior of a modern establishment for the distillation of volatile oils by steam, as carried on by Messrs. Schimmel & Co., at Leipzig, Germany, to whom the author is indebted for the loan of this and other illustrations shown in this chapter. Whenever the volatile oil is deeply imbedded in the material, as in the case of cloves, cubebs, and many barks and seeds, it is necessary that this first be reduced to a coarse powder so as to facilitate the liberation of the oil. The distillate, which is a mixt

FIG. 210.

short one near the top; as the distillate cools, it separates into two distinct layers, one consisting of pure oil and the other of water

ure of oil and water, is collected in suitable receivers, either in the form of Florentine flasks with a single outlet tube near the bottom and reaching nearly to the top, as shown in Fig. 208, or of tall cylinders provided with two tubes, a long one near the bottom and a

holding some oil in solution and suspension, which is subsequently regained, either by conveying the water back direct to the still or by distilling the water in separate stills, frequently after the addition of table salt to facilitate separation of the oil. As a rule, the layer of oil floats on top, except in those cases in which the oil has a specific gravity above 1.000, as the oils of cloves, cassia, gaultheria, etc. The lower layer will flow off through the long tube as soon as the liquid in the flask or cylinder reaches the height of the curve in the tube, and will continue to flow as long as distillation continues. When the upper layer fills the vessel, the latter must be changed; or if it is provided with two tubes, as shown in Fig. 209, the liquid will pass out through the short tube into another receptacle; thus the two layers of liquid are withdrawn simultaneously almost as fast as separation takes place.

The contrast between modern distillation of volatile oils by steam and former crude methods still practised in some countries, is. strikingly shown in the two illustrations representing the distillation of oil of rose. Fig. 210 represents a complete steam plant for distillation of the oil, at Leipzig, Germany, from flowers grown in the near-by districts. In Fig. 211 is shown the arrangement of a copper still extensively used by the Bulgarians at the present time, which is capable of accommodating a charge of about 22 pounds of freshly gathered roses and 20 gallons of water.

Besides distillation, other methods are employed for obtaining volatile oils, such as expression by hand or machine, and extraction by means of suitable solvents; for certain flowers possessing delicate fragrance, such as the violet, heliotrope, mignonette, tuberose, etc., which do not contain volatile oils in appreciable quantities, the treatment with fats by maceration and digestion, or the pneumatic process, is resorted to for obtaining the odorous principles.