Tetronal. This compound, (C2H),C(SO,C,H)2, chemically known as diethylsulphonyl-diethylmethane, resembles sulphonal in appearance, and has been used in place of the latter. It is made like sulphonal, except that diethylketone is used in place of acetone for the preparation of mercaptol.

Tri

Trional. (CH,C,H ̧)C(SO,C,H ̧)2.-If methylethylketone be used in place of acetone in the manufacture of mercaptol, the latter upon oxidation will yield a compound of the above constitution, and chemically known as diethylsulphonyl-methylethylmethane. onal is more extensively used than either of the two preceding compounds, which it closely resembles in appearance and properties. It is recognized in the German Pharmacopoeia as methylsulphonal, and is soluble in about 320 parts of water at 15° C. (59° F.).

Urethane. While in chemistry the term urethane is applied to all ethers of carbamic acid, in pharmacy and medicine it is restricted to one compound, namely, ethylurethane or ethyl carbamate, NH,COOCH. It can be obtained in several ways, but for medicinal use is prepared by heating in a sealed tube a mixture of urea nitrate and alcohol for several hours at a temperature of 120°-130° C. (248°-266° F.); the resulting crystalline mass is dissolved in water and shaken with ether, which latter extracts the urethane and yields it in crystals upon distillation, which may be purified further by recrystallization from water. Phenylethylurethane, NHCH, COOC,H,, is known in commerce as euphorin.

CHAPTER LVII.

FATS AND FIXED OILS.

THE physical properties of these compounds have been considered on pages 202-203. Chemically, they belong to the class of esters, or ethereal salts, being readily resolved into the respective acids and alcohols by means of alkali hydroxides. The constitution of fats and fixed oils was first studied and announced by Chevreul in 1811. With a few exceptions, the basylous radical is the same for all fats and fixed oils, whether obtained from the vegetable or animal kingdom, namely, glyceryl or propenyl, CH, a trivalent group derived from the hydrocarbon propane, CH, the alcohol or hydroxide of which is glycerin or propenyl alcohol, C,H,(OH),; other bases obtainable from fats are cholesterin, myricin, cerotin, cetin, etc. The acid radicals found in fats are many, the chief ones being oleic, palmitic, stearic, arachic, capric, erucic, lauric, and myristic acids, varying from one to three or four in number for a single fat or fixed oil.

The ordinary fats and oils used in pharmacy consist, for the most part, of two or three compound ethers, to which the names olein, palmitin, and stearin have been given; of these, olein, being always liquid, naturally forms the chief constituent of fixed oils, while palmitin and stearin, being solid at ordinary temperatures, by their presence determine the firmer consistence of solid fats. All three are fatty acid esters of glyceryl, known respectively to chemists as glyceryl trioleate, C,H,(CHO), glyceryl tripalmitate, CH(CHO), and glyceryl tristearate, CH(CHO); the names glycerides of oleic, palmitic, and stearic acid are also applied to them. The oleic acids derived from different oils, not having a uniform composition and properties, specific names are employed to distinguish the respective glycerides; thus, olein, CH,(CH3O2), linolein, CH(CHO), and physetolein, CH,(CH2O2); the first named occurs both in animal and vegetable fats, the second only in vegetable fats, while the third is confined to vegetable fats, chiefly fishoil, seal oil, etc.

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The following true fats, recognized in the Pharmacopoeia, are mixtures of glyceryl esters:

Animal Fats.-Lard, composed of about 60 per cent. of olein and 40 per cent. of a mixture of stearin and palmitin. Lard oil is almost pure olein with small and varying proportions of palmitin

and stearin, dependent upon the care with which the oil has been expressed. Suet consists of about 75 or 80 per cent. of stearin and palmitin and 20 or 25 per cent. of olein. Codliver oil contains in its crude state about 70 per cent. of physetolein, 25 per cent. of palmitin together with small quantities of stearin and other glycerides; its acid character is due to the presence of free fatty acids. It is said also to contain organic compounds of iodine, bromine, phosphorus, and sulphur, as well as trimethylamine, asellin, C25,HN4?, morrhuin, C,HN,?, and morrhuic acid, C,HNO? Morrhuol, said to represent the active virtues of codliver oil, is obtained by treating the latter with 90 per cent. alcohol and distilling the liquid after filtration; it constitutes the oily residue left in the still, and has a disagreeable odor and a sharp, bitter taste.

Vegetable Fats.—Almond oil (expressed) is probably the purest form of olein, containing only very small quantities of the esters of linoleic and the solid fatty acids; hence it can be cooled to near -20° C. (-4° F.) without congealing. Castor oil consists chiefly of ricinolein, CH(CHO), which differs from olein in being the glyceride of an acid containing in each molecule one more oxygen atom than oleic acid; small quantities of stearin also are present. It differs from other fixed oils in being readily soluble in alcohol and insoluble in benzin, petroleum, and paraffin oils. Cottonseed oil is a mixture of olein, palmitin, and linolein; it contains also a small proportion of a non-saponifiable body. In its crude state the oil contains albuminous and resinous matter, to which latter the dark color is due. Croton oil contains olein, palmitin, stearin, and the glycerides of a number of other fatty acids. The vesicating and purgative action of croton oil is, according to the latest investigations of Kobert, due to crotonolic acid, which exists in the oil both in the free state and as a glyceride, and can be extracted by means of alcohol. Linseed oil, when pure, consists of 80 or 90 per cent. of linolein, the remainder being made up of stearin, palmitin, olein, etc. Its property of absorbing oxygen and increasing in weight is explained elsewhere. Olive oil is a mixture of about 70 per cent. of olein, 5 per cent. of linolein, and 25 per cent. of palmitin and arachin, the latter two glycerides being present in greater proportion in the lower grades of the oil. The green color is due to chlorophyll in solution. Sesame oil contains olein, palmitin, and stearin. Oil of theobroma, or cacao butter, is composed of the glycerides of oleic, palmitic, stearic, lauric, and arachic acids.

Among the fat-like bodies used in pharmacy which do not contain the radical glyceryl, the following derivations of monatomic alcohols may be named: Beeswax, which consists of myricyl palmitate, C3H6C6H1O2, and free cerotic acid, HCHO, with small quantities of free melissic acid. Spermaceti is chiefly cetyl palmitate, CH.CHO, which, during the life of the sperm whale, is held

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in solution in sperm oil or cetinelain. Lanolin is a mixture of various compound ethers of cholesterin and isocholesterin, CHOH, the official article containing also 30 per cent. of water. Neither beeswax, spermaceti, nor lanolin can be saponified by boiling with an aqueous solution of potassa; hence they can readily be separated from true fats and free fatty acids with which they may be associated. Cholesterin fats are easily distinguished from glycerin fats by the appearance of a pink color, gradually changing to green or blue, when concentrated sulphuric acid is allowed to drop slowly into a solution of 0.1 Gm. of the fat (lanolin) in 3.5 Cc. of acetic anhydride, (C2H2)2O; fatty acid glycerides do not show this color

reaction.

When absolutely pure, fats and fixed oils are without action on litmus, but in the presence of air, light, and moisture decomposition and oxidation gradually ensue, an unpleasant odor, due to the formation of volatile products, and an acid reaction being observed. Fats are not affected by a temperature of 100° C. (212° F.), but at 250° C. (482° F.) they are decomposed, various volatile products being formed, among which is an irritating, odorous substance, called acrolein, which, chemically, is allyl aldehyde, C,H,O or CH,CHCHO, and is derived from the decomposition of the glycerin present in fats.

The division of fixed oils into drying and non-drying oils has been mentioned on page 203; to the first class belongs linseed oil, while olive oil and expressed oil of almond are representatives of the second class. A third class might be named, embracing those oils which partake of some of the properties of both the drying and non-drying oils; this class includes castor oil, cottonseed oil, and sesame oil. This difference in their behavior when exposed to air is due to slight differences in chemical composition, linseed oil being a glyceride of linoleic acid, CHO, which, upon exposure to air, absorbs oxygen and is converted into oxylinolein, CHO, or linoxin, a neutral amorphous elastic mass, which is insoluble in alcohol and ether, but dissolves in a mixture of alcohol and chloroform. Investigations have shown linoleic acid to be a mixture of variable proportions of three other acids beside oleic acid, which former alone are concerned in the gradual solidification of drying oils. The smaller the proportion of oleic acid present in drying oils, the more rapidly and thoroughly will the oil solidify upon exposure; this explains why oils belonging to the same group with cottonseed oil, dry so much more slowly and imperfectly than the members of the linseed oil group. The glyceride of oleic acid present in drying oils behaves like that of the non-drying oils, but decomposition is probably estopped by the formation of the other oxidation-products; hence the unpleasant odor and acidity before mentioned are not observable in true drying oils.

Non-drying oils, consisting chiefly of the glyceride of oleic acid, with varying proportions of palmitin, upon exposure to air, appear

to absorb water and split up into free oleic (and palmitic) acid and glycerin, the latter being oxidized gradually into carbon dioxide and water, and thus disappearing. The oleic acid absorbs oxygen and is gradually converted into oxystearic acid and finally into volatile odorous acids, such as capronic, valerianic, etc. This process of decomposition is termed rancidification, and explains the condition termed rancidity noticed in old and carelessly preserved fats and fixed oils. By some it is thought that the change is superinduced by the presence of mucilaginous or albuminous matter in the fat, acting as a ferment under the influence of light, air, and moisture. Rancid fats, therefore, always contain free acid and yield less glycerin than sweet fats when saponified.

In the chemical examination of fats and fixed oils for adulterations, etc., two reactions are especially employed by analysts, namely, that with potassium hydroxide and that with iodine. In the first case 1 or 2 Gm. of the fat or oil are boiled with a definite volume, 25 Cc., of alcoholic solution of potassium hydroxide, of known strength, in a flask in a water-bath until saponification is complete-usually about fifteen minutes-and an excess of alkali remains; the excessive alkali is determined volumetrically with deci- or semi-normal acid, and thus the quantity of alkali used for saponifying the fat ascertained; from this the number of milligrammes of potassium hydroxide required by 1 Gm. of any fat or fixed oil is calculated, which is called Koettstoerfer's saponification number of that particular fat or oil.

The iodine test depends upon the fact that fats are capable of combining with varying quantities of iodine and forming colorless addition-products under certain favorable conditions. Two solutions are used for this test, which is known as Hübl's iodine test, namely, one, consisting of 5 Gm. of iodine in 100 Cc. of 95 per cent. alcohol, and another consisting of 6 Gm. of pure mercurie chloride in 100 Cc. of 95 per cent. alcohol. Equal volumes of the two solutions are mixed and allowed to stand for twenty-four hours in a well-closed bottle, after which the iodine value of the mixture is determined by titration with decinormal sodium thiosulphate solution. The fats or fixed oils are then tested at once, as follows: 0.2 Gm. of drying oils, 0.4 Gm. of non-drying oils, or 0.8 Gm. of solid fats, is weighed into a 500 Ce. flask and dissolved in 10 Cc. of chloroform, after which 25 Ce., or in the case of drying oils 40-60 Cc., of the above iodine mixture are added; if after agitation the liquid is not clear, a little more chloroform must be added. The flask is tightly closed and set aside for two hours, when the mixture should still remain highly colored, otherwise 10 or 15 Cc. more of the iodine mixture are added and the flask set aside for two hours more. About 20 Cc. of a 10 per cent. aqueous solution of potassium iodide are now added, as also 150 Cc. of water and decinormal sodium thiosulphate added from a burette, with frequent agitation, until both the aqueous and chloroformic