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Such are the directions given in most of I)r. Duncan's editions of the New Edinburgh Dispensatory, for the depuration of the decoctions, and we have inserted them at full length, because, although we doubt very much of their propriety, our reasons for so doing are scarcely more than hypothetical. We would advise the decoctions to be evaporated, after they have been filtered, boiling hot, without any further depuration; because some of the most active principles of vegetable substances, such as tannin, are much more soluble in boiling than in cold water, and because almost all of them are very quickly affected by exposure to the atmosphere. Therefore, if a boiling decoction, saturated with tannin, be allowed to cool, the greatest part of the very principle on which the activity of the substance depends will separate to the bottom, and according to the above directions, will be thrown away as sediment. The same objection applies more strongly to allowing the decoction to cool, and deposit a fresh sediment, after it has been partially evaporated. Besides, by allowing the decoctions to stand several days before we proceed to their evaporation, we are in fact allowing the active principles contained in the decoction to be altered by the action of the air, and to be converted into substances, perhaps inactive, which also are thrown away as sediment. The evaporation is most conveniently performed in broad shallow vessels: the iarger the surface of the liquor, the sooner will the aqueous parts exhale. This effect may likewise be promoted by agitation. When the matter begins to grow thick, great care is necessary to prevent, its burning. This accident, almost unavoidable if the quantity be large, and the fire applied as usual under the evaporating pan, may be effectually prevented, by carrying on the inspissation, after the common manner, no further than the consistence of a syrup, when the matter is to be poured into shallow tin or earthen pans, and placed in an oven, with its door open, moderately heated; which, acting uniformly on every part of the liquid, will soon reduce it to any degree of consistence required. This may likewise be done, and more securely, by setting the evaporating vessel in boiling water; but the evaporation is in this way very tedious. Alcohol is much too expensive to be

employed as a menstruum for obtaining extracts, except in those cases where water is totally inadequate to the purpose. The cases are, 1. When the nature of the extract is very perishable when dissolved in water, so that it is liable to be decomposed before the evaporation can be comleted, especially if we cannot proceed immediately to the evaporation. 2. When water is totally incapable of dissolving the substance to be extracted; and, 3. When the substance extracted can bear the heat of boiling alcohol without being evaporated, but would be dissipated by that of boiling water; that is, when it requires a heat greater than 176°, and less than 212°, for its evaporation. In the last case, the alcohol, must be perfectly free from water, because the heat necessary to evaporate it at the end of the process would frustrate the whole operation. Hence, also, the subject itself ought always to be dry: those substances which lose their virtue by drying, lose it equally on being submitted to this treatment with the purest alcohol. In this way the alcoholic extract of some aromatic substances, as cinnamon, lavender, rosemary, retain a considerable degree of their fine flavour. In the second case, the alcohol need not be so very strong, because it is still capable of dissolving resinous substances, although diluted with a considerable proportion of water. In the first case, the alcohol may be still much weaker: or rather, the addition of a small proportion of alcohol to water will be sufficient to retard or prevent the decomposition of the decoction. The alcohol employed in all these cases should be perfectly free from any unpleasant flavour, lest it be communicated to the extract. The inspissation should be performed from the beginning in the gentle heat of a water-bath. We need, not suffer the alcohol to evaporate in the air: the greatest part of it may be recovered by collecting the vapour in common distilling vessels. If the distilled spirit be found to have brought over any flavour from the subject, it may be advantageously reserved for the same purpose again. When diluted alcohol is employed, the distillation should only be continued as long as alcohol comes over; and the evaporation should be finished in wide open vessels. Pure resins are prepared, by adding to spirituous tinctures of resinous vegetables

a large quantity of water. The resin, incapable of remaining dissolved in the watery liquor, separates and falls to the bottom, leaving in the menstruum such other principles of the plant as the spirit might have extracted at first along with it. But this is only practised for the purpose of analysis.

Eactracts made with water only.

Extractum gentianæ. lutea’, Edin. extract of gentian. Having cut and bruised any quantity of gentian, pour upon it eight times its quantity of water. Boil to the consumption of one half of the liquor, and strain it by strong expression. Evaporate the decoction immediately to the consistence of thick honey, in a bath of water saturated with muriate of soda. In the same manner are prepared extracts. Of the roots of liquorice, extractum glycyrrhizae glabrae. Of the roots of black hellebore, extractum hellebori nigri. Of the leaves of rue, extractum rutae graveolentis. Of the leaves of senna, extractum cassiae Sennae. Of the flowers of chamomile, extractum anthemidis nobilis (chamoemeli). Of the heads of white poppy, extractum papaveris albi. Of logwood, extractum haematoxyli Campechensis. Extract of broom tops, extractum cacuminis genistae. Extract of chamomile, extractum chamoemeli. Extract of savin, extractum sabinae. The other extracts of this division are, Extractum cinchonae, Lond. extract of Peruvian bark. Extractum haematoxyli, Lond. extract ef logwood.

Extractum opii, Dubl. extract of opium.

Extractum sennae, Lond. extract of Senna.

Bactracts made with .Allcohol and Water.

Extractum cinchonae officinalis, Fdin. extractum cinchonae cum resina, Lond. resin of bark.

Extractum radicis convolvuli jalapae, Edin. extractum jalapii, Lond. resin of jalap.

Extractum cascarillae, Lond, resin of cascarilla.

Extractum colocynthidis compositum, compound extract of colocynth. CLAss XX. Pulveris. Powdens. This form is proper for such materials only, as are capable of being sufficiently dried to become pulverisable without the loss of their virtue. There are several substances, however, of this kind, which cannot be conveniently taken in powder; bitter, acrid, foetid drugs are too disagreeable; emollient and mucilaginous herbs and roots are too bulky; pure gums cohere, and become tenacious in the mouth; fixed alkaline salts deliquesce when exposed in the air, and volatile alkalies exhale. Many of the aromatics, too, suffer a great loss of their odorous principles when kept in powder;" as in that form they expose a much larger surface to the air. The dose of powders, in extemporaneous prescription, is generally about half a drachm: it rarely exceeds a whole drachm, and is not often less than a scruple. Substances which produce powerful effects in smaller doses are not trusted to this form, unless their bulk be increased by additions of less efficacy; those which require to be given in larger ones are better fitted for other forms. The usual vehicle for taking the kohter powders is any agreeable thin liquid. The ponderous powders, particularly those prepared from metallic substances, require a more consistent vehicle, as syrups; for from thin ones they soon subside; resinous substances, likewise, are most commodiously taken in thick liquors, for in thin ones they are apt to run into lumps, which are not easily again soluble. Pulvis aloes cum canella, Lond.powder of aloes with canella. Pulvis aloeticus cum guaiaco, Lond. powder aloetic with guaiacum. Pulvis aloeticus cum ferro, Lond. powder aloetic with iron. Pulvis aromaticus, Lond. Dubl. powder aromatic. Pulvis asari compositus, Lond. Dubl. powder of asarabacca compound. Pulvis cretae compositus, Lond. pulvis carbonatis calcis comp. Edin. powder of chalk, compound. Pulvis cretae compositus cum opio, Lond. powder of chalk, compound with opium. Pulvis chelarum cancri compositus, Lond. powder of crab's claws, compound.

Pulvis cerussae compositus, Lond. powder of ceruse, compound. Pulvis contrayerva, comp. Lond, powder of contrayerva, compound. Pulvis ipecacuanhae comp. Lond. pulvis ipecacuanhae et opii. Edin. powder of Dover. Pulvis myrrhae comp. Lond, powder of myrrh, compound. Pulvis scammonii comp. Lond. Edin. Dubl. powder of scammony, compound. Pulvis scammonii comp. cum aloe, Lond. powder of scammony compound with aloes. Pulvis scammonii comp. cum calomela, Lond, powder of scammony with calomel. Pulvis sennae compositus, Lond. powder of senna, compound. Pulvis sulphatis aluminae comp. Edin. powder of styptic. Pulvis tragacanthae compositus, Lond. powder of tragacanth, compound. CLAss XXI. Confectiones. Confections. Under this head we include all those preparations which have hitherto been loosely denominated conserves, electuaries, and confections; the difference in the preparation of which being too trifling for distinct heads. Confections are, for the most part, compositions of recent vegetable matters and sugars, beaten or otherwise mixed together into an uniform mass. The sugar should be pounded by itself, and passed through a sieve before it be mixed with the vegetable mass, for without this it cannot be properly incorporated. It is obvious that, from the large admixture of sugar, only substances of considerable activity can be taken with advantage in this form. Conserves are hence, for the most part, only auxiliary to medicines of greater activity; as, for example, for reducing into boluses or pills the more ponderous powders, as calomel, oxides of iron, and other mineral preparations. Electuaries are composed chiefly of powders mixed up with syrups, &c. into such a consistence, that the powders may not separate in keeping, that a dose may be easily taken up on the point of a knife, and not prove too stiff to swallow. Electuaries receive chiefly the milder alterative medicines, and such as are not ungrateful to the palate. The more powerful drugs, as cathartics, emetics, opiates, and the like(except in officinal electuaries to be dispensed by weight,) are seldom trusted in this form, on account of the un

certainty of the dose; disgustful ones, acrids, bitters, foetids, cannot be conveniently taken in it; nor is the form of an electuary well fitted for the more ponderous substances, as mercurials, these being apt to subside on keeping, unless the composition be made very stiff. The lighter powders require thrice their weight of honey, or syrup boiled to the thickness of honey, to make them into the consistence of an electuary: of syrups of the common consistence, twice the weight of the powder is sufficient. Where the common syrups are employed, it is necessary to add likewise a little conserve, to prevent the compound from candying and drying too soon. Electuaries of Peruvian bark, for instance, made up with syrup alone, will often, in a day or two, grow too dry for taking. This is owing to the crystallization of the sugar. Deyeux, therefore, advises electuaries, confections, and conserves, to be made up with syrups from which all the crystallizable parts have been separated. For this purpose, after being sufficiently evaporated, they are to be exposed to the heat of a stove as long as they form any crystals. The syrup which remains, probably from the presence of some vegetable acid, has no tendency to crystallize, and is to be decanted and evaporated te a proper consistence. In hospital practice, the same object may be obtained much more easily by using molasses instead of syrups. The quantity of an electuary directed at a time, in extemporaneous prescription, varies much, according to its constituent parts, but is rarely less than the size of a nutmeg, or more than two or three ounces. The conservae are, Citri aurantii, Edin. aur. hispalensis, Lon. conserve of orange-peel. Rosae caninae, Edin. cynosbati, Lond. conserve of hips. Rosae rubrae, Edin. Lond. rosae, Dubl. conserve of red rose-buds. Lujulae, Lond. acetosellae, Dubl. conserve of wood sorrel. Pluck the leaves from the stalks, the unblown petals from the cups, taking off the heels. Take the outer rind off the oranges by a grater. When prepared in this way, beat them with a wooden pestle in a marble mortar, first by themselves, afterwards with three times their weight of double refined sugar, until they be mixed. The only exceptions to these general directions, which are those of the London college, are, that the London college adds only twenty ounces of sugar to one pound of the pulp of hips, and that the Dublin add only twice their weight of sugar to the sorrel leaves. La Grange says, that by infusing the red rose leaves in four times their weight of water, which is af. terwards to be expressed from them, they lose their bitterness, and are more easily reduced to a pulp, which he then mixes with a thick syrup, prepared by dissolving the sugar in the expressed liquor, and boiling it down to the consistence of an electuary.

It is scarcely necessary to make any particular remarks on these conserves. Their taste and virtues are compounded of those of sugar, and the substance combined with it. The wood sorrel and hips are acidulous and refrigerant; the orange rind and worm-wood bitter and stomachic, and the red rose buds astringent.

The electuaries and confections are as follow : Electuarium cassiae, Lond. Dubl. electuarium cassiae fistulae, Edin. electuary of cassia. Electuarium cassiaesennae, Edin. electuarium sennae, Lond. electuary lenitive. Electuarium catechu, Edin. electuary of catechu. Electuarium catechu comp. Dubl. electuary of catechu, compound. Electuarium scammonii, Lond. Dubl. electuary of scammony. Electuarium opiatum, Edin. confectio opiata, Lond. electuary of opium, opiate confection. Confectio aromatica, Lond. aromatic confection.

Class XXII. Trochisci. Troch Es.

Troches and lozenges are composed of powders made up with glutinous substances into little cakes, and afterwards dried. This form is principally made use of for the more commodious exhibition of certain medicines, by fitting them to dissolve slowly in the mouth, so as to pass by degrees into the stomach; and hence these preparations have generally a considerable proportion of sugar or other materials grateful to the palate. Some powders have likewise been reduced into troches, with a view to their preservation; though o for no very good reasons; for the moistening, and afterwards drying them in the air, must in this light be of greater injury, than any advantage accruing from this form can counterbalance,

VOL. IX.

Trochisci cretae, Lond. trochisci carbo. natis calcis, Edin. troches of chalk. Trochisci glycirrhizae, Lond. Dubl. troches of liquorice. Trochisc glycirrhizae cum opio, Edin. Dubl. troches of liquorice with opium. Trochisci amyli, Lond. troches starch. Trochisci gummosi, Edin. troches of starch with gum arabic. Trochisci magnesiae, Lond. troches of magnesia. Trochisci nitri, Lond, trochisci nitratis potassae, Edin. troches of nitre. Trochisci sulphuris, Lond. troches of sulphur.

CLAss XXIII. Pilule. PILLs.

The masses for pills are best kept in bladders, which should be moistened now and then with some of the same kind of liquid that the mass was made up with, * or with some proper aromatic oil. When the mass is to be divided into pills, a given weight of it is rolled out into a cylinder of a given length, and of an equal thickness throughout, and is then divided into a given number of equal pieces, by means of a simple machine. These pieces are then rounded between the fingers; and to prevent them from adhering, they are covered either with starch, or powder of liquorice, or orris root. In Germany the powder of lycopodium is much used. To this form are peculiarly adapted those drugs which operate in a small dose, and whose nauseous and offensive taste or smell require them to be concealed from the palate. Pills should have the consistence of a firm paste, a round form, and a weight not exceeding five grains. Essential oils may enter them in small quantity : deliquescent salts are improper. Efflorescent salts, such as carbonate of soda, should be previously exposed so as to fall to powder: deliquescent extracts should have some powder combined with them. The mass should be beaten until it become perfectly uniform and plastic. Powders may be made into pills with extracts, balsams, soap, mucilages, bread-crumb, &c. Gummy resins, and inspissated juices, are sometimes soft enough to be made into pills, without addition : where any moisture is requisite, spirit of wine is more proper than syrups or conserves, as it unites more readily with them, and does not sensibly increase their bulk. Light dry powders require syrup or muf

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cilages: and the more ponderous, as the mercurial and other metallic preparations, thick honey, conserve, or extracts. Light powders require about half their weight of syrup; or of honey, about threefourths their weight; to reduce them into a due consistence for forming pills. Half a drachm of the mass will make five or six pills of a moderate size. Gums and inspissated juices are to be first softened with the liquid prescribed: the powders are then to be added, and the whole beat thoroughly together, till they be perfectly mixed. Pilulae aloeticae, Edin. Dubl. pills aloetic. Pilulae aloes compositae, Lond. pills aloetic, compound. Pilulae aloes cum asafoetida, Edin. pills aloetic with asafoetida. Pilulae aloes cum colocynthide, Edin. pills aloetic with colocynth. Pilulae aloes cum myrrha, Lond. pillso aloetic with myrrh. Pilulae asafoetida compositae, Edin. pills of asafoetida, compound. Pilulae galbani compositae, Lond. pills of galbanum, compound. Pilulae ammoniareti cupri, Edin. pills of ammoniaret of copper. Pilulae hydrargyri, Lond. Edin. Dubl. pills of quicksilver. Pilulae opii, Lond. pilulae opiatae, Edin. pills of opium. Pilulae rhei compositae, Edin. pills of rhubarb, compound. Pilulae scillae, Lond. Dubl. Edin. pills of squills. Pilulae stibii compositae, Dubl. pills of antimony, compound; Plummer's. The common mercurial pill is one of the best preparations of mercury, and may, in general, supersede most other forms of this medicine. In its peparation the mercury is minutely divided, and probably eonverted into the black oxide. To effect its mechanical division it must be triturated with some viscid substance. Soap, resin of guaiac, honey, extract of liquorice, manna, and conserve of roses, have all been at different times recommended. The soap aud guaiac have been rejected, on account of their being decomposed by the juices of the stomach; and the honey, because it was apt to gripe some people. With regard to the others, the grounds of selection are not well understood; perhaps the acid contained in the conserve of roses may contribute to the extinction of the mercury. We learn when the mercury is completely extinguished most easily, by rubbing

a very little of the mass with the point of the finger on a piece of paper, if no globules appear. As soon as this is the case, it is necessary to mix with the mass a proportion of some dry powder, to give it a proper degree of consistency. For this Fo powder of liquorice root has een commonly used; but it is extremely apt to become mouldy, and to cause the pills to spoil. The Edinburgh College have, therefore, with great propriety, substituted for it starch, which is a very inalterable substance, and easily procured at all times in a state of purity. It is necessary to form the mass into pills immediately, as it soon becomes hard. One grain of mercury is contained in four grains of the Edinburgh mass, in three of the London, and in two and a half of the Dublin. The dose of these pills must be regulated by circumstances; from two to six five-grain pills may be given daily,

CLAss XXIV. Cataplasmata. CATAPLASMs,

By cataplasms are generally understood those external applications, which are brought to a due consistence or form for being properly applied, not by means of oily or fatty matters, but by water or watery fluids. Of these many are had recourse to in actual practice; but they are seldom prepared in the shops of the apothecaries, and in some of the best modern Pharmacopoeias no formula of this kind is introduced. The London and Dublin Colleges, however, although they have abridged the number of cataplasms, still retain a few : and it is not without some advantage that there are fixed forms for the preparation of them. Cataplasma aluminis, Lond. Coagulum aluminis, Dubl. cataplasm of alum, alum curd. Cataplasma cumini, Lond. cataplasm of cummin, London treacle. Cataplasma sinapeos, Lond. Dubl. cataplasm of mustard. Cataplasms of mustard are commonly known by the name of sinapisms. They were formerly frequently prepared in a more complicated state, containing garlic, black soap, and other similar articles; but the above simple form will answer every purpose which they are capable of accomplishing. They are employed only as stimulants: they often inflame the part and raise blisters, but not so perfectly as cantharides. They are frequently applied to the soles of the feet in the low state of acute diseases, for raising the

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