60 per cent. of alcohol. A menstruum composed of alcohol 2 volumes, glycerin 2 volumes, and water 6 volumes, has been found to yield a very satisfactory preparation, which precipitates but slightly, mixes clear with syrup, and retains the odor of hydrocyanic acid for a long time. Repercolation is best adapted for this fluid extract, since its value depends chiefly upon the volatile hydrocyanic acid, which is generated during the maceration and percolation of the drug.

Extractum Rhei Fluidum. The very large proportion of alcohol directed in the official formula has been found necessary after a series of experiments with various mixtures of alcohol and water, both with and without the addition of glycerin. The present fluid extract precipitates only very slightly, and retains its original fluidity for several years, but does not form clear mixtures with aqueous or saccharine liquids unless an alkali be added.

Extractum Sanguinaria Fluidum. This fluid extract formerly caused much annoyance by copious precipitation on the bottom and sides of the containers. The presence of 5 per cent. of acetic acid and a less alcoholic menstruum have been found to improve the character of the preparation, but precipitation can probably never be entirely prevented.

Extractum Sarsaparilla Fluidum. Since glycerin has been dropped from the official menstruum, a slight increase in the alcoholic strength appears desirable, and although water alone is capable of extracting the virtues of sarsaparilla, a mixture of 2 volumes of alcohol and 3 volumes of water will yield a better and more stable preparation.

Extractum Scilla Fluidum. A strongly alcoholic menstruum is desirable for squill, as the drug contains much gummy and albuminous matter, which would affect the stability of the fluid extract.

Extractum Scutellaria Fluidum. When made with diluted alcohol this fluid extract does not keep so well as when made with 2 volumes of alcohol and 1 volume of water; hence the latter mixture is to be preferred.

Extractum Senega Fluidum. Ammonia water is used in the menstruum, to form soluble compounds with the pectin principles present in the drug, and thus prevent gelatinization of the fluid extract. The active virtues of senega are far more soluble in water than in alcohol, but the former also extracts larger proportions of pectin compounds, and these must be avoided as far as possible. A menstruum composed of 2 volumes of alcohol and 1 volume of water, with the addition of 5 per cent. of ammonia water, exhausts the drug thoroughly and yields a permanent preparation, hence the stronger alcoholic menstruum ordered by the Pharmacopoeia is unnecssary.

Extractum Stillingia Fluidum. This fluid extract will sometimes gelatinize on standing; this may be avoided either by using a stronger alcoholic menstruum (alcohol 3 volumes, water i volume), or, what is still better, by adding sugar in the proportion of 10 or 12 per cent. of the weight of the drug.

Extractum Tritici Fluidum. Although the Pharmacopoeia directs percolation with boiling water to exhaustion, digestion of the finelycut drug will be found preferable in every way, the operation to be repeated once or twice as may be necessary; the infusion should then be rapidly concentrated, and when cold mixed with alcohol and set aside for two days, whereby the mucilaginous and albuminous matter is separated. The finished product contains 25 per cent. of alcohol, which protects the saccharine liquid against fermentation.

Extractum Uva Ursi Fluidum. The large quantity of glycerin, 30 per cent, contained in the official fluid extract, is probably necessary in connection with the very weak alcoholic menstruum ordered, but a preparation keeping equally well can be made by using diluted alcohol and omitting the glycerin entirely.

Extractum Veratri Viridis Fluidum. There seems to be little or no necessity for this preparation, as the drug is well represented by the tincture. If carefully made, the fluid extract is two and a half times as strong as the tincture, and presents all the alkaloids and resins of the drug, in the form of a concentrated solution.

CHAPTER XXIII.

EXTRACTS.

EXTRACTS are permanent, soft, solid, or dry preparations, obtained by evaporation of a solution of the medicinal principles of drugs. These solutions are prepared, as a rule, in the manner already explained under fluid extracts, the solvents or menstrua employed being either water, water and alcohol, alcohol, or ether, according to the different menstrua used in their manufacture. Extracts are divided into aqueous, hydro-alcoholic, alcoholic, and ethereal, the lastnamed class being recognized in the Pharmacopoeia under the name of oleoresins. In fresh plants, the solution of the medicinal principles is represented by the juice, and may be obtained by expression; extracts prepared by simple evaporation of the fresh juice of a plant are usually known as inspissated juices.

Our Pharmacopoeia recognizes but one extract made from the fresh plant, extract of taraxacum, since the narcotic herbs which are extensively used in Europe for this purpose are not indigenous to this country. The juice is obtained from the fresh plant, after removal of extraneous matter, by bruising in a stone mortar with the aid of a hard-wood pestle until reduced to a smooth pulpy mass, which is then strongly expressed in canvas bags; in order to recover all the juice, the residue is often mixed with water and again expressed. When the plant is not sufficiently moist to enable the formation of a soft pulp, water is sprinkled over it from time to time, as directed in the Pharmacopoeia.

Besides the medicinal principles, the expressed juices of fresh herbs contain also mucilaginous and albuminous matter in solution and variable quantities of chlorophyll or green coloring matter in suspension; of these the albuminous principles are most objectionable, as upon concentration of the juice they undergo change and are apt to render the finished extract tough and insoluble. When roots are

expressed, as in the case of the corm of colchicum, starch, which is present in the juice in place of chlorophyll, passes through the presscloth, and must be removed by subsidence and decantation. The British, German, and French Pharmacopoeias direct the removal of albuminous matter by heating the juice to from 80° to 90° C. (176° to 194° F.) and filtering. The coagulated albumen envelops the green coloring matter and removes it also, which fact is disregarded in Germany and France, and accounts for the brown color of the extracts made from fresh herbs in those countries. In Great Britain the chlorophyll is carefully separated by heating the fresh juice to

55° C. (131° F.) and straining through calico; the liquid is then heated to 93.3° C. (200° F.) and after filtering out the coagulated albumen, evaporated to a thin syrup, the chlorophyll is reincorporated and evaporation continued, with constant stirring, to the proper consistence. This explains the firm condition and fine green color of the British narcotic extracts. The German Pharmacopoeia alone provides for the removal of the gummy matter, and hence its narcotic extracts are relatively much stronger than those of England and France. The solubility of gummy matter is not in any way affected by heating, and, therefore, the filtered liquid, after removal of the coagulated albumen and chlorophyll, is evaporated to 10 per cent. of the original weight of the fresh herb used, mixed with an equal volume of alcohol and set aside for twenty-four hours to allow the precipitated gum to subside. After decantation the precipitate is washed with diluted alcohol, which is added to the other clear liquid, and the whole evaporated to the condition of a soft solid.

Considerable quantities of British extracts are annually imported into this country, and preferred by many pharmacists on account of their pilular consistence. In the case of the narcotic extracts, the superiority of the solid extracts made from the fresh juice of the herb is questionable, owing to the variability in the amount of extract obtained from fresh plants; besides, it must not be overlooked that the same name in the United States and British Pharmacopoeias does not always indicate the same preparation, as, for instance, Extractum Aconiti, Extractum Belladonna Alcoholicum, and Extractum Conii.

CONSISTENCE OF EXTRACTS. The Pharmacopoeia recognizes two kinds of solid extracts, those of pilular consistence and those evaporated to complete dryness. A pilular consistence is such a condition as will allow the extract to be rolled into masses of pilular form without adhering to the fingers or subsequently losing shape; this is rarely met with in the market, except in the case of British narcotic extracts, which derive their firmness chiefly from the chlorophyll and gummy matter present. Pilular consistence for the extracts made in this country, by the official formulas, is practically unattainable at all seasons, for extracts made in summer are apt to become too hard in winter, whilst those evaporated to the proper consistence in winter are apt to soften in summer. Some extracts are apt to become tough and hard in the course of time, such as cinchona, quassia, and rhubarb; these are best retained in proper condition by incorporating with them, while still warm, 10 per cent. of their weight of glycerin, as suggested in the Pharmacopoeia. The condition of complete dryness is not applicable to all extracts, but can be readily maintained for all those so directed by the Pharmacopia, provided heat and moisture be excluded.

CHANGES BY EVAPORATION. All plants contain one or more principles, which, though originally colorless, are very easily altered under the influence of air and heat, acquiring a yellow or brown color.

It is not known whether the so-called colorless extractive is alike in all plants, neither is its composition or the nature of the changes produced under the conditions mentioned known, except that the heat of boiling water and the prolonged action of oxygen will convert it ultimately into a blackish insoluble substance, to which the name apotheme has been given, and which appears to be allied to humin. Extractive is almost insoluble in absolute alcohol and ether, but dissolves freely in weaker alcohol and water, and is removed from its solution by animal charcoal and aluminum hydroxide, the more readily after it has become colored by oxidation. It is with difficulty freed from all admixtures, and the terms sweet, bitter, acrid, etc., as applied to extractives, refer to the same body in a more or less altered condition, combined or intimately mixed with other principles to which the peculiar taste is due. The injurious influence of air and heat upon the vegetable juices is mainly confined to the alterations of this extractive, and extends, in a limited degree only, to the majority of the well-defined principles. Its effects have often been much overrated, except as regards the appearance of the extracts. The color of the different extracts varies with the nature of the drug from which they have been made, but should never be black. The characteristic taste, and to some extent also the odor of the drug, should be perceived in the extracts, and these should yield a nearly clear or moderately turbid solution with the menstruum used in their preparation.

AQUEOUS EXTRACTS. While decoction in some cases increases the yield of extract, by bringing into solution starch and other inert matter, it more frequently injures the quality of the product, by inducing changes in certain principles, which do not occur by infusion at lower temperatures. There is but one instance, that of extract of logwood, in which the Pharmacopoeia directs extraction by boiling, and this is on account of the difficulty of exhausting the tough wood. In Europe, digestion is still preferred for a few aqueous extracts, but, as a rule, maceration and percolation with cold water have been found to yield superior extracts. For the better extraction of the active virtues of the drug, an addition of acid or alkali is sometimes made, as in the case of the official extracts of colchicum root and pure extract of glycyrrhiza. In the preparation of aqueous extracts the solution is freed from objectionable matter, whenever necessary, by heating to the boiling-point and straining before final evaporation.

In 1889, the plan of concentrating large volumes of aqueous solutions of extracts by means of cold was formulated by M. Adrian, a French pharmacist, and put into practice on a large scale. Following up the suggestions of Herrera (1877), M. Adrian subjects the filtered aqueous solutions to a temperature of -20° C. (-4° F.), in an ammonia-ice apparatus, and thus obtains large blocks of ice, in which the extractive solution is enveloped, the pure water alone freezing; these blocks of ice are rapidly converted into snow, by means of