Cooley's Cyclopaedia of Practical Receipts Volume I Part 223

_Prep._ The preparation of medicinal extracts may be conveniently considered under two divisions, viz.--1. The production of a solution of the soluble portion of the substances operated on; and, 2. The reduction of this solution by evaporation to the consistence of an extract.

1. PREPARATION OF SOLUTIONS:--The preliminary operations in the manufacture of extracts are similar to those employed in the preparation of DECOCTIONS, INFUSIONS, and TINCTURES. The proper quant.i.ty of the ingredients being taken, the whole is well bruised or reduced to coa.r.s.e powder, or otherwise divided by slicing with a knife, that every portion may be fully exposed to the solvent action of the fluid. In some few cases (as with gentian, &c.) the 'slicing,' or reduction to fragments, is often conveniently deferred until the action of the menstruum shall have so far softened the ingredients as to render them of easy division by the knife.

Those substances (as sarsaparilla, chamomiles, &c.) whose medicinal principles reside in the cortical portion, of which are of easy solubility, are commonly subjected to the action of the menstruum without being subjected to any particular preparation.

In the preparation of AQUEOUS EXTRACTS, the ingredients are treated with water until all the soluble matter that it is desirable to obtain is dissolved out. There are several methods of effecting this object, depending upon the nature of the substances acted on. In some cases maceration in cold water is resorted to; in others percolation with that fluid in a 'displacement apparatus.' More generally, however, boiling water is poured on the substance, and is digested on it for some time, as in the preparation of infusions; or the substance is exhausted by boiling in water, as in the preparation of decoctions. After the ebullition or infusion has continued a sufficient time, the heat is removed, and the liquid portion drawn off. The ingredients are then pressed to extract the remaining liquid; or they are washed or 'sparged' with hot water, which expels it by displacement. According to the usual practice in the majority of cases, a second quant.i.ty of water is poured on after the first has been thoroughly drained off, and the effusion or decoction is repeated a second and even a third time, or until the ingredients are perfectly exhausted of their soluble portion. The liquor or liquors thus obtained being allowed to repose for 15 or 20 minutes, for the purpose of depositing the sand or other gritty and heavy matter that is mechanically mixed with them, are carefully decanted from the sediment, and, after being run through a fine hair-sieve, or flannel bag, are ready for concentration. In some instances, however, this method proves insufficient to render the liquid clear. In such cases, the solution may generally be rendered transparent by clarification with a little white of egg, removing the sc.u.m as it rises, straining the liquid through flannel, as before; or the liquid may be filtered through a bag made of fine 'Welsh flannel,' or of 'tweeled cotton cloth' (Canton flannel), both of which should be soaked in clean water for at least an hour before use. In the small way, filters of linen or paper are sometimes employed; but as all media sufficiently fine to render vegetable solutions transparent soon choke up, this filtration is objectionable, from the length of time it occupies. In some houses the aqueous infusion or decoction is allowed to repose for 24 hours, and then decanted and evaporated; but such a plan is objectionable, as, however smooth and glossy extracts so prepared may appear, their medicinal virtues are lessened by the lengthened exposure to the atmosphere.

When about one half of an aqueous solution has evaporated, it is often advantageous to repa.s.s it through a flannel or horsehair strainer, to remove the flocculi that generally form by the action of the heat and air.

This is especially necessary with vegetable solutions prepared without boiling, and should be adopted whenever a smooth and slightly extract is desired.

II. REDUCTION OF SOLUTIONS:--The reduction of the solution to the proper consistence is effected by evaporation. The mode in which this is performed varies for different extracts. The London College directs that, "unless otherwise ordered, the evaporation should be conducted as quickly as possible, in a broad, shallow pan, placed in a water bath, until a proper consistence is acquired for forming pills; stirring a.s.siduously with a spatula towards the end of the operation." The Dublin College orders that "all simple (aqueous) extracts (EXTRACTA SIMPLICIORA), unless otherwise ordered, are to be prepared by boiling the vegetable matter in 8 times its weight of water, till the liquid is reduced to one half; the liquor is then to be expressed, and, after a short time allowed for defecation, to be decanted, filtered, and evaporated in a steam or water bath, until it begins to thicken, and then finally insp.i.s.sated by a reduced heat, with continual stirring, until a consistence for forming pills be attained." The instructions of the Edinburgh College are similar, with the one important exception, however, of ordering the evaporation to be conducted in a water bath saturated with chloride of sodium.

Though the water bath has the sanction of the London College, it is ill adapted for the purpose to which it is here ordered to be applied, as from its low evaporative power the advantages which are derived from its equable temperature are vastly overbalanced by the lengthened exposure of the solution in a heated state to the action of the atmosphere. It has been shown that a vegetable extract so prepared is inferior in quality to a similar one formed by rapid evaporation in a shallow pan over a naked fire, or placed in a sand bath, provided proper care is taken, and a.s.siduous stirring is adopted during the whole time of the exposure to heat. In practice, however, the use of a naked fire is perfectly inadmissible, as the least neglect on the part of the operator would probably lead to the incineration of the whole. These objections are obviated by the addition of the 1/5th part of salt to the water of the bath, which raises its boiling-point to 218-3/4 Fahr., when the temperature of the contained extract is fully 212; the remaining 6 being lost by the interposition of the substance of the evaporating vessel.

ON THE LARGE SCALE, the evaporation of infusions or decoctions for extracts is usually conducted in very wide, shallow, copper or tinned-copper pans, having steam-tight jackets of cast iron, and heated by steam 'playing' between the two.

The rapid deterioration which vegetable juices and solutions undergo by exposure to the air, especially at high temperatures, has led to the introduction of apparatus, by which they may be concentrated without contact with the atmosphere, and at a less degree of heat than is required for that purpose in open vessels. Such is the method, commonly called 'Barry's process,' in which the air is removed from certain air-tight refrigerators by the introduction of steam, which is then condensed by the application of cold, by which means a partial vacuum is obtained. Another process for attenuating the atmosphere over the surface of fluids during evaporation is by the action of an air-pump. This plan was introduced by Howard, and is commonly applied to the concentration of syrups in the sugar refineries. Extracts obtained by either of these methods are said to be prepared 'in vacuo,' and are found in practice to be immensely superior to the common extracts of the shops, and consequently require to be exhibited in proportionably small doses.

'The American Journal of Pharmacy' for September, 1877, contains a new process for the preparation of extracts without heat, by Professor Herrara. We extract the following from the Professor's paper:--

"The results of my observations have satisfied me that, when the water partially congeals, the dissolved principles remain in solution in the mother liquors, and that two or three congelations are generally sufficient for obtaining the solutions concentrated enough to finish the extract by exposure upon plates to the heat of the sun, or of a drying closet, heated to about 30 cent. (86 Fahr.). The extracts prepared by this method accurately represent the properties of the plants, and the principles which are changed by the influence of heat remain unaltered; even the volatile const.i.tuents are not dissipated, though most of the water be removed by freezing. Owing to the small cost of the necessary apparatus, it appears to me that my process for preparing extracts should be preferable even in those countries where ice is less readily obtainable than combustibles.

"Extract of conium prepared with unpurified juice by the process mentioned, has preserved the characteristic odour of conia, and by dissolving it in water. I have obtained a solution exactly representing the juice of the plant in appearance and properties, and giving when heated an abundant coagulation, proving that even alb.u.men had remained unaltered. 1750 grams of cow's milk at 9 R., left, after three congelations, 750 grams of a liquid having a density of 148, and by evaporation in the sun this left a dry extract of milk, which again formed that liquid on being dissolved in water. A number of other liquids similarly treated, gave corresponding results, and it seems to me, therefore, that medicinal extracts are best prepared by congelation. It may be objected that the medical juices should be previously purified, but it should be remembered that coagulated alb.u.men always encloses a considerable portion of the active principles, and that the heat necessary to effect the coagulation and the evaporation by means of a water-bath is sufficient to change many principles; also that the extracts thus prepared are sometimes inert or less active. The careful experiments made by Orfila and the clinical experience of others demonstrate that extracts prepared with unpurified juice are stronger.

"The apparatus employed by me is the so-called sorbetiere;[294] for larger quant.i.ties the apparatus of Gougaud is preferable. The frigoric mixture is composed of ice and sodium chloride, or preferably of crystallised calcium chloride. After a large portion of the solution has congealed, the ma.s.s is enclosed in a cloth and subjected to pressure, the press-cake of ice is broken and again pressed, to separate the mother liquor as completely as possible, and the congelation is repeated two or three times, with the precaution that it is not carried far enough to cause the precipitation of the sparingly soluble principles. The mother liquor is then put into shallow dishes and exposed to the heat of the sun or of a drying room, the temperature of which does not exceed 30 C. (86 F.) until the extract has attained the desired consistence."

[Footnote 294: An apparatus similar to that used for ice-cream.]

_Obs._ When water, acidulated with acetic acid, is employed in the preparation of extracts, the vegetable substances are usually macerated in it, in the cold, or the dilute acid is sprinkled over the bruised plant in the fresh or recent state, and the whole is then submitted to strong pressure, to expel the juice, which is strained and evaporated in the usual way, but preferably in a well-tinned or plated-copper pan.

ALCOHOLIC and SPIRITUOUS EXTRACTS are prepared by evaporating a filtered concentrated tincture of the ingredients in any suitable vessel, by which the volatilized spirit may be saved. In general, rectified spirit is used as the menstruum; but in some cases proof spirit is employed; and, in others, the substances are first digested in proof spirit, and afterwards in water, and the mixed tincture and infusion evaporated in the usual manner.

ETHEREAL EXTRACTS are obtained in a similar manner to alcoholic ones; but being merely prepared in small quant.i.ties at a time, the process may be conveniently performed in gla.s.s vessels. When it is required to boil either of the above fluids (alcoholic or ethereal), or any other volatile liquid on the ingredients, a vessel fitted with a long tube, or a Liebig's condenser reversed, as noticed under ether, may be used to prevent any loss of the menstruum.

The INSp.i.s.sATED VEGETABLE JUICES (JUICES, E.; SUCCI, L.) of the British Pharmacopia are obtained by expressing the juices from the fresh plants, and preserving them by the addition of spirit. "By thus preserving the juice of the plant its properties are not impaired by the action of the air during the time necessary to dry the leaf for tincture, nor by the action of both air and heat during the time necessary to evaporate the juice to the consistence of an extract."--Squire. The directions of the Edinburgh College for preparing their insp.i.s.sated juices (SUCCI Sp.i.s.sATI, L.) are--"Beat the fresh substance, and press it strongly through a canvas bag, in order to obtain the juice; which, being put into a wide, shallow vessel, and heated by means of boiling water saturated with sea-salt, is to be reduced to the consistence of honey. The ma.s.s, when cold, is to be put into glazed earthen vessels, and moistened with strong alcohol." By operating in this way a considerable portion of the activity of narcotic vegetables is lost. Some of their juices, as that of aconite, are impaired in so short a time as scarcely to compensate for the trouble of preparing them. This deterioration does not, however, take place in any remarkable degree, if the expressed juice from the recent vegetable be evaporated by exposing it in a thin stratum to a current of very dry air, as adopted by Mr Squire. This may be managed by putting the juice into small, flat trays or dishes, placed on shelves in a suitably arranged apparatus, alternated with similar vessels of concentrated sulphuric acid; or by causing a current of very dry air, at the common temperature of the atmosphere, to pa.s.s over them. It has been shown that 10 gr. of extract, thus prepared, were more than equal to 20 gr. prepared _in vacuo_; and to more than 60 gr., and in some cases, 90 gr., of those prepared by the common process of boiling down the juice to an extract.

The concluding portion of the process of extract-making, technically termed 'finishing-off,' requires the most scrupulous attention. As the evaporation advances, the heat should be lessened, and as soon as the extract acquires the consistence of thick treacle it should be removed altogether, and the remainder of fluid matter evaporated by the heat retained by the copper pan, the escape of vapour being promoted by a.s.siduous and laborious stirring with a suitably shaped wooden spatula.

This part of the process should be continued until a proper consistence is attained and the extract is nearly cold. When high-pressure steam or a chloride of calcium bath is employed, care must be taken to withdraw the heat before stirring the semi-liquid ma.s.s; as, if an extract having a temperature of about the boiling-point of water, or even a few degrees below it, is agitated, it becomes full of bubbles, and appears rough and puffy, and this appearance cannot be removed by subsequent stirring, or by any method but redissolving it in water and re-evaporation. This is especially the case with the extracts of sarsaparilla (simple and compound), gentian, liquorice, and most others of a similar cla.s.s. A good laboratory man knows from experience the proper time for the removal of the heat, but unpractised persons often fail in this particular. In such cases should the heat retained by the evaporating pan, and by the extract, prove insufficient to complete the process, a little more may be cautiously applied. Without a.s.siduous and laborious stirring in the way described, a very smooth and glossy extract cannot be produced. To promote this artificial appearance, some persons add 3% or 4% each of olive oil and gum arabic, dissolved in water, with about 1% or 2% of spirit of wine.

The consistence of the ordinary extracts of the shops is the same as that of electuaries and confections, and is described in the Ph. E. as equal to that of "thick honey." The instructions of the Ph. L. and D., to evaporate the ma.s.s "until it acquires a consistence proper for making pills," except in 2 or 3 cases (as _Ext. Colocynth. Comp._, &c.), is not adopted, and, indeed, would be found inconvenient in practice. Extracts evaporated to such a consistence are commonly termed 'pilular extracts,' and when evaporated so that they are quite dry, and brittle when cold, they are called 'hard extracts' (EXTRACTA DURA, L.).

_Pres._ Extracts should be put into pots as soon as taken from the pan, and, after being carefully and securely tied over with bladder, should be 'stored' in a dry situation. The London College orders "a small quant.i.ty of rectified spirit to be sprinkled upon all the softer extracts, to prevent them becoming mouldy." A better way is to employ a little spirit, holding in solution a few drops of oil of cloves, or a still less quant.i.ty of creasote. This should be added to them the last thing before removing them from the evaporating pan, and when they are nearly cold. The same object is effected by moistening the inside of the bladder (used to tie them over) with a few drops of oil of cloves or creasote. Hard extracts should be kept in bladders or gut skins, placed in stone pots, and well covered over. With care, extracts prepared from recent vegetable substances may be preserved twelve months, or from season to season; and those from dry ingredients, or such as are less inclined to spoil, for perhaps double that time; but beyond these periods their virtues cannot be relied on, and they should consequently be discarded, if remaining unused or unsold.

_Pur., &c._ The quality of an extract cannot be ascertained by mere inspection, nor is it readily discovered by chemical tests. A knowledge of these facts has induced the mercenary and fraudulent manufacturer to employ damaged and inferior drugs in their preparation, alike regardless of the welfare of the patient and the credit of the pract.i.tioner. A common practice with some manufacturers is, not only to pick out the least expensive variety of every drug for the preparation of their extracts, but the most inferior and often damaged and worthless portion of this already inferior article. The production of a smooth, bright, and glossy extract is all that is usually attempted by these individuals, and all that is sought after by the ma.s.s of purchasers, who mistake the simulation of the mere external signs of good quality for its actual existence. It is a fact, which we can verify from extensive experience in the laboratory, and from years of practical observation on this point, that extracts faithfully prepared from good materials do not possess the sightly and pleasing appearance of those commonly vended by the wholesale druggists.

On comparing the extracts prepared by different metropolitan houses, we have found that those which have exhibited a remarkably bright and glossy appearance have been uniformly inferior, and sometimes nearly inert; whilst others, with a less prepossessing appearance, have been generally of good quality. These facts are well established by reference to the extracts of those houses and inst.i.tutions that are remarkable for the superior quality of their preparations, and by comparing them with the common extracts of the shops supplied by the wholesale trade.

A good extract should be--1. Free from grit, and wholly soluble in 20 parts of the menstruum employed in its preparation, forming a nearly clear solution.--2. It should have a uniform texture and colour, and be of a proper consistence.--3. If a narcotic or active extract, it may be exhibited in proper doses, and its effects watched. Its activity may also be tested on any small animal.--4. An a.s.say for the proximate vegetable principle (alkaloid, &c.) contained in the plant from which it has been prepared may be made. The extracts prepared from the expressed juices of plants, without straining off the coagulated alb.u.men, are, of course, exceptions to the first test. Unfortunately, these tests are not always easily performed, and the last two are inapplicable to those extracts that exercise no very marked physiological action, unless when taken in repeated doses, long continued. This want of a ready means of accurately testing the qualities of extracts has enabled the fraudulent manufacturer to sell inferior articles with impunity, and often without the least fear or danger of detection.

In general, an extract more than six months old contains only half the activity of a similar one newly made. When more than twelve months old they should be rejected as worthless, and the stock renewed.

_Uses, &c._ The extracts of the shops are generally acknowledged to be the most varying, imperfect, and uncertain cla.s.s of medicines belonging to modern pharmacy. They are mostly used in the same cases as the plants from which they are prepared, but in smaller doses.

_Concluding Remarks._ In the preparation of extracts the great desiderata to be aimed at are--to suit the menstrua and the methods of manipulating to the peculiar characteristics of the active const.i.tuents of the vegetable substances operated on. The pharmaceutist should always bear in mind that a perfect extract should be a concentrated, solid ma.s.s, representing, as near as possible, in medicinal efficacy, the materials from which it has been prepared, and capable of being redissolved, so as to form a solution closely resembling that from which it has been derived.

An extract possessing equal strength to the whole ma.s.s of the ingredients from which it has been prepared is almost next to an impossibility, however desirable such a degree of perfection may be. The medicinal properties of all solutions of vegetable matter are injured by being reduced to the solid state; and this deterioration, more or less, takes place, whether the solvent be water, acetic acid, proof spirit, or alcohol. The volatile portions (the essential oils, the aroma, &c.) are nearly or wholly dissipated; and though these do not always form the princ.i.p.al or active ingredients of the vegetables from which extracts are prepared, yet they generally exercise a modifying and controlling influence over the other ingredients, which considerably alters their therapeutical action. The loss of aroma may often be a trifling deficiency, but in the extracts of aconite, henbane, hemlock, belladonna, and other narcotic plants, this is not the case. In these cases it is well known that the inert preparations are wholly deficient of the odour of the recent plant, and that in proportion as the odour is developed, so is their activity preserved. The powerful smell of the recently expressed juice of hemlock, with the scarcely perceptible odour of the extract (EXTRACTUM CONII, Ph. L.), offers an excellent example of this fact. The dose of the one often reaches 20 or 30 gr., whilst that of the other seldom exceeds 5 or 10 drops, or a portion equivalent in dry ingredients to considerably less than 1/2 gr.

When extracts are ordered in prescriptions, those of the 'Pharmacopia'

should be alone employed by the dispenser, as the subst.i.tution of others for them would not only be violating faith with the prescriber, but might also produce consequences alike injurious to the dispenser and the patient. Many medical gentlemen prefer extracts prepared by particular processes or persons, but such intention is always indicated in their prescriptions.

=Extract of Ac'onite.= _Syn._ EXTRACT OF WOLFSBANE, E. OF MONKSHOOD, INSp.i.s.sATED JUICE OF ACONITE; EXTRACTUM ACONITI (B. P., Ph. L. E. & U.

S.), SUCCUS Sp.i.s.sATUS ACONITI (Ph. D. 1826), L. _Prep._ 1. (B. P.) Take 112 lbs. of the fresh leaves and flowering tops, bruise them, press out the juice, heat it gradually to 130 F., and separate the green matter by a calico filter. Heat the strained liquor to 200 F. to coagulate alb.u.men, and again filter. Evaporate the filtrate by a water bath to the consistence of a thin syrup; then add to it the green colouring matter previously separated, and stirring the whole together a.s.siduously, evaporate at a temperature not exceeding 140 F. to a pill consistence.--_Dose_, 1 to 2 gr.

2. (Ph. L.) Take of fresh leaves of aconite, 1 lb.; bruise them in a stone mortar, express the juice, and evaporate it, unstrained, to a proper consistence. The formulae of the Ph. D. & U. S. are similar.

3. (Ph. E.) Beat the fresh leaves of aconite to a pulp, and express the juice, then subject the residuum to percolation with rectified spirit until the latter pa.s.ses through without being materially coloured; unite the expressed juice and the percolated tincture, filter, distil off the spirit, and evaporate in a vapour or a water bath to a proper consistence.

Stronger than the preceding.

_Obs._ A variable and uncertain preparation. Numbness and tingling follow its application to the limbs or tongue when it is of good quality.--_Product._ 1 cwt. of fresh leaves yield between 5 lbs. and 6 lbs. of extract. _Prop._ Anodyne, sudorific, and narcotic; very poisonous.--_Dose_, 1/2 gr. to 2 gr., made into a pill with liquorice powder; once or twice a day, in neuralgic pains, chronic rheumatism, glandular swellings, &c., gradually and cautiously increased to 5 or 6 gr.

4. (Alcoholic; E. A. ALCOHOLIc.u.m, L.)--_a._ (P. Cod.) Aconite (in coa.r.s.e powder), 1 lb.; proof spirit, 3-1/2 lbs. (say 2-1/2 pints); proceed by the method of displacement, and when all the spirit has penetrated the powdered ma.s.s, keep this covered with distilled water, until the liquid begins to cause a precipitate in falling into that which has previously pa.s.sed through; next distil the spirit from the tincture, and evaporate the residuum to the proper consistence.

_b._ (Ph. U. S.) Aconite 1 lb.; spirit, sp. gr. 935 (= 13 u. p.), 1 quart, or q. s.; as last.

_c._ (Ph. Baden.) From the tincture prepared with rectified spirit, and by either maceration or displacement. Stronger than the last two.

_d._ (Ph. Bor.) The juice is expressed from the fresh herb, which is then sprinkled with about 1/3 of its weight of water, and again pressed; the mixed and strained liquid is evaporated in a vapour bath, at 122 to 140 Fahr., to about one half; to this, as soon as cold, an equal weight of spirit (sp. gr. 900) is added, and after frequent agitation for 24 hours, the whole is filtered, with pressure; the marc is treated with fresh spirit (equal to about 1-4th that first used) and again pressed; the mixed liquors are next filtered, and are, lastly, evaporated, as before, to the proper consistence.

_Obs._ Resembles the simple extract, but is much more powerful. It has been exhibited internally in the form of pills, and used externally, combined with ointment or spread on simple plaster.--_Dose_, 1/12 to 1/6 gr. every three hours.

5. (Ammoniated; E. A. AMMONIATUM, L.--Dr Turnbull.) Extract of aconite, 1 dr.; liquor of ammonia (strongest), 10 or 12 drops; mix.

6. (Dried); E. A. SICc.u.m, L.--P. Cod.) The expressed juice, strained through a sieve or coa.r.s.e linen, is at once, without depuration, exposed in earthen dishes, in layers of about 2 lines deep, in a stove or current of dry air, to a temperature ranging between 95 and 104 Fahr., until reduced to dryness. The dried extract is to be packed in bottles.

7. (Saccharated; E. A. SACCHARATUM, L.) From extract of aconite (Ph.

Bor.), 4 oz.; sugar of milk (in powder), 1 oz.; mix, and dry the ma.s.s in a warm place, adding sugar of milk, q. s. to make the whole equal in weight to that of the extract used (4 oz.). An excellent preparation, which keeps well. The other NARCOTIC EXTRACTS, as those of BELLADONNA, HEMLOCK, HENBANE, &c., are to be treated in a similar manner. See ACONITE, and _below_.

=Extract of Aconite Root.= _Syn._ EXTRACTUM ACONITI RADICIS ALCOHOLIc.u.m, L. _Prep._ (Dr Fleming; Dr Turnbull.) From a tincture of the root made with rectified spirit. It is said to be 12 times as strong as the extract of the leaves.

=Extract of Ag'aric=. _Syn._ EXTRACTUM AGARICI, L. _Prep._ (P. Cod.) From the infusion of white agaric (_Polyporus officinalis_) prepared with cold water. Purgative.--_Dose_, 1 to 4 gr.

=Extract of Alcorno'co.= _Syn._ EXTRACTUM ALCORNOCae, L. _Prep._ From a decoction of alcornoco bark (South American). Astringent and tonic.--_Dose_, 5 to 20 gr. in phthisis, &c.

=Extract of Al'oes.= _Syn._ PURIFIED ALOES, WASHED A.; EXTRACTUM ALOeS BARBADENSIS (B. P.), EXTRACTUM ALOeS (Ph. L.), E. A. AQUOSUM (Ph. D.), L.

_Prep._ 1. (B. P.) Barbadoes aloes, in small pieces, 1 lb.; treated with 1 gall. of boiling water for 12 hours, and the clear liquid evaporated.--_Dose_, 1 to 3 gr. B. P. 2 to 6 gr.

2. (B. P.) Socotrine aloes, 1 lb., treated with 1 gall. of boiling water for 12 hours, and the clear liquid evaporated to dryness.

3. (Ph. D.) Aloes (hepatic), 4 oz.; water, 1 quart; boil till dissolved; when cold, decant the clear liquid, and evaporate as before.

4. (Ph. Bor. 1847.) By macerating powdered aloes in cold water for 48 hours, with frequent agitation, and then evaporating in a water bath at a temperature not exceeding 150 to 165 Fahr., until a pilular consistence is attained.