moulds and cooled. This constitutes yellow wax, from which white wax is made by a process of sun-bleaching, as follows: Melted wax is again solidified in the form of thin ribbons or bands by allowing it to flow over wet revolving cylinders; these bands are moistened with water, and exposed to sunlight in the open air. After exposure for some time the color disappears in spots and the wax is again melted, resolidified, and treated as before, the process being repeated until the wax is completely bleached, when it is finally melted and run into moulds; besides losing its color, wax thus treated is somewhat changed by long exposure to light and air, and is more disposed to rancidity than yellow wax, as is noticeable in the modified odor. Pure yellow wax melts at 63° to 64° C. (145.4°-147.2° F.), white wax at 65° C. (149° F.); they differ from true fats in not containing glycerin, and in not forming soap when boiled with solution of alkali carbonates. Wax is completely dissolved by ether and chloroform, but not by boiling alcohol and cold benzene or carbon disulphide. Besides the crude adulterations readily observed in melted wax, tallow and other fats, as well as vegetable wax, resin, and paraffin, are occasionally mixed with it; they can be readily detected by the pharmacopoeial tests.

Almond Oil (Oleum Amygdala Expressum, U. S. P.).—Expressed oil of almond is commercially better known as oil of sweet almond, although large quantities of the oil are obtained from the bitter almond. The yellowish color of the oil is due entirely to the colored episperm, for if blanched almonds be expressed a colorless oil will be obtained. The oil remains perfectly clear if cooled to -10° C. (14° F.), and does not congeal until a temperature of -20° C. (-4° F.) is reached. It is often adulterated with the expressed oils of apricot and peach kernels, and also other fixed oils, for which the Pharmacopoeia gives appropriate tests.

Castor Oil (Oleum Ricini, U. S. P.).-This oil is obtained by expression from the seed of the plant popularly called palma christi, the finest quality being secured by cold expression. It differs from other fixed oils in being soluble in all proportions of absolute alcohol and in 3 times its volume of a mixture of 19 volumes of official alcohol and 1 volume of water. Castor oil is rarely adulterated.

There are at present six mills in this country where castor oil is expressed-one each in Jersey City, N. J.; Kansas City, Mo.; East St. Louis, Ill., and Memphis, Tenn., and two in St. Louis, Mo. The seed, or castor-bean, as it is called, from which the oil is expressed, is produced in the states of Illinois, Kansas, and Missouri, and in Oklahoma Territory, but the chief supply of late years has come from British India. The origin of the name castor oil is somewhat in doubt. The plant, having been introduced into the West Indies shortly after the discovery of this country, was mistaken by the Spaniards for an entirely different plant-the Vitex angus castus-and named by them agno casto, from which the English coined the word castor and probably applied the name to the oil.

Cottonseed Oil (Oleum Gossypii Seminis, U. S. P.).—The official cottonseed oil is refined bleached oil, for the crude product, obtained by hydraulic pressure from the seed, has a brown color and linseedlike odor, and contains considerable quantities of albuminous matter. After subsiding, the crude oil is treated with superheated steam, and finally well shaken with heated weak alkali solution. The yield of oil from cottonseed varies from 12.5 to 20 per cent. It congeals when cooled to 0° or -5° C. (32° or 23° F.), and is instantly colored dark reddish-brown on contact with concentrated sulphuric acid; it belongs to the drying oils, but shaken with nitric acid and water it gradually forms a colored semisolid mass. The chief use of cottonseed oil is as a substitute for more expensive fixed oils, as in the case of some of the official liniments, and there is no doubt that it is extensively employed as an adulterant for almond, olive, and other oils.

Croton Oil (Oleum Tiglii, U. S. P.).-While fresh croton oil requires from 50 to 60 times its weight of alcohol for solution, the solubility increases materially with age. The oil does not congeal until cooled to -16° C. (3.2° F.). Although it belongs to the class of non-drying oils, it remains liquid if vigorously shaken with fuming nitric acid and water and then allowed to stand for 1 or 2 days; this behavior distinguishes croton oil from other non-drying oils and serves to detect adulteration with the latter.

Linseed Oil (Oleum Lini, U. S. P.).-Much of the linseed oil offered is expressed with the aid of heat, as thereby the yield is increased nearly 50 per cent. Like expressed oil of almond, linseed oil does not congeal until cooled to -20° C. (-4° F.). It is soluble in an equal volume of official alcohol, but becomes turbid if the proportion of alcohol is doubled. Linseed oil is one of the best drying oils known. The so-called boiled linseed oil of commerce should never be used in pharmacy.

Olive Oil (Oleum Olivæ, U. S. P.). Various grades of olive oil are found on the market, the best being that commercially known as Virgin Olive Oil, which is obtained by cold expression from the flesh only of the ripe olive. It is of a pale-yellow or light greenish-yellow color, and becomes cloudy at 10° C. (50° F.), congealing to a whitish, granular mass at 0° C. (32° F.). Much of the olive oil offered for sale is adulterated with cottonseed oil, groundnut oil, or sesame oil.

Oil of Theobroma (Oleum Theobromatis, U. S. P.).-This oil, better known as cacao butter, is the only official fixed oil solid at ordinary temperature. It is obtained to the extent of 40 per cent. by expression between hot plates from the roasted seeds of the cacao tree, which subsequently yield the well-known cacao mass or chocolate. While brittle at 15° C. (59° F.), it melts readily at the temperature of the human body, and for this reason is admirably adapted for use as a vehicle in making suppositories. Cacao butter is subject to adulteration with tallow, stearin, and paraffin, the presence of which can be detected by the low fusing-point and the high congealing-point of the oil.

Volatile oils are mixtures of those substances to which, in a

majority of cases, the peculiar odors of plants are due. Although the attribute volatile is indicative merely of a physical property which most of these substances have in common, and in nowise refers to their source, the designation volatile oil has been restricted entirely to volatile products from the vegetable kingdom. In recent years the term has been made to include artificial substances identical with, or at least closely related to, such natural plant products. Volatile oils do not all preëxist in the plant, some being the result of fermentative action between certain constituents of the plant in the presence of water, and others being produced by destructive distillation. Volatile oils may exist in every part of the plant from the root to the seed, and when several oils are present in different parts of the same plant they will generally be found to differ in physical as well as chemical properties; as, for instance, the oils of orange obtained from the leaf, flower, and rind. Volatile oils usually occur in separate cells, as glands in the herbaceous portion and rinds of many fruits, or distributed throughout the interior tissue, or forming distinct oil tubes, as in the fruit of fennel, anise, etc. The odor of volatile oils, while in some instances due to their particular composition, in others appears to be due to atmospheric influences, since oil of turpentine and other oils when rectified in an atmosphere of carbon dioxide have been found devoid of all unpleasant odor, and yet, when again exposed to the air, they soon acquired their characteristic odor. With few exceptions, volatile oils are lighter than water, and their solubility in water is very variable; their specific gravities at 25° C. (77° F.) range from 0.845 to 1.180. Absolutely pure volatile oils are colorless, but the commercial varieties are frequently colored yellow, green, blue, red, and brown; the color in most instances disappears when the oil is brought into solution. Many volatile oils are completely soluble in glacial acetic acid, and all are soluble in alcohol, but in proportions varying from less than an equal volume to ten or more. They have but few properties in common with fixed oils, but like these are soluble in ether, chloroform, and carbon disulphide. Freshly prepared volatile oils are generally freely soluble in benzin, but after exposure they gradually lose this property, and often form turbid mixtures when shaken with the same. When dropped upon filtering paper they cause a stain somewhat resembling that of fixed oils, but which is dissipated upon the application of heat; the stain produced by old or partly resinified volatile oils frequently cannot be removed by heat, but can be readily distinguished from the stain of fixed oils by its shining, varnish-like appearance and by its complete removal with the aid of warm alcohol, the stain from fixed oils being devoid of lustre and insoluble in alcohol. Volatile oils are inflammable, and burn with a bright but sooty flame; exposed to air and light they are more or less rapidly oxidized, being gradually converted into a viscid oil, and finally even into a solid resin. They never become rancid in the sense mentioned under fixed oils, and do not contain

glycerin. Owing to the changes which volatile oils undergo through exposure to light and air, they should be preserved in well-stoppered bottles in a dark place; amber- or yellow-colored glass is best adapted for oil containers, as it intercepts the actinic rays of light. The addition of deodorized alcohol or Cologne spirit will also preserve the fine aroma of such oils as lemon and orange, not more than 5 per cent. by volume being necessary. Resinified oils may

Distillation of oil of star-anise in Tonquin, Asia.

be restored by redistillation with water or weak alkali, or, if in small quantities, by Cuvier's method, which consists in shaking the oil for fifteen or twenty minutes with a magma formed of animal charcoal and a solution of borax, whereby the resinified portion is

united to the borax and the oil becomes limpid. The whitening of corks in bottles containing volatile oils is due to the presence of ozone produced by the gradual oxidation of the oil.

The adulterations to which volatile oils are subjected are fixed oils, alcohol, and highly rectified petroleum; frequently, also, the higher-priced oils are mixed with cheaper and inferior oils. Fixed oils are easily detected by a permanent greasy stain upon paper, and by a non-volatile residue when the suspected oil is subjected to distillation. Alcohol may be tested for in several ways. If the oil be shaken in a graduated tube with an equal volume of water or glycerin, and then allowed to stand at rest, any diminution in the volume of the oil would indicate alcohol, and approximately also the proportion present; if considerable alcohol be present, the characteristic lambent blue flame of burning alcohol will be observed if a portion of the suspected oil is ignited in a dark room; fused

calcium chloride and dry potassium acetate are insoluble in volatile oils, but in the presence of alcohol become soft and even liquid, depending upon the proportion of alcohol; potassium acetate and