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Maceration

When an infusion is made without the aid of heat it is termed If an infusion is required of dried leaves or flowers, they are first moistened with a little boiling water, and a time allowed for them to maceration. This takes a much longer time swell and soften before adding the rest of the than an infusion, properly so called; it rarely water. Infusions made by adding all the requires less than 7 days, sometimes several water at once, as is still frequently practiced, weeks. Those substances to which heat are deficient both in flavor and perfume. The would be injurious, or which are easily soluinfusion of tea is an every-day illustration of this; as all who can make a good cup of tea know how necessary it is to first draw the tea with a small portion of water; and yet, strange to say, this principle is utterly neble, are treated in this way. In many distillations this method is made use of to soften the substances before putting into the still; and to facilitate the extraction of their odorous principle. Tinctures, when prepared by maceration, into the instrument, being very careful not to should be frequently shaken during the prohave the powder too coarse or loosely pressed, cess, which should be conducted in glass or it will permit the liquid to pass too quickly; vessels well stopped. and on the other hand it should not be too 40. Digestion is a prolonged infusion fine and compact, or it may offer an unneceswhich is usually conducted at a medium tem- sary resistance. Should the liquor flow too perature between that required for an infusion , rapidly, return it to the instrument, and close properly so called, and that of a maceration. it beneath for a time, and thus permit the Its object is usually to impregnate alcohol with the principles of a substance which would be but slowly extracted without the aid of a certain amount of heat, such as that of the sun or of hot ashes.

Mixing together two or more liquors and allowing them to stand for some days, is also called digestion.

Maceration and digestion are usually performed in vessels of stoneware or glass, which are placed on the sand-bath, in cases where a regular and uniform heat is required.

Whatever may be the form or nature of the vessels employed, care must be taken not to fill them full, also to cover those which are to be placed on the sand-bath with a damp piece of parchment tightly tied round the top, with many pin holes pricked in it. If this latter precaution be neglected, the increased finer parts of the powder to subside, and cause a slower percolation. by all who have made sufficient trial of it to The method of percolation is now preferred apply it correctly.

The first portion of liquid obtained by the method of displacement is always in a state of high concentration. In general it is a simple solution of the soluble ingredients of the crude drug in the fluid employed. But sometimes the solvent, if compound, is resolved into its compound parts, and the fluid which passes through it at any given time is only one of these, holding in solution only the most soluble parts of the drug.

Thus, if diluted alcohol be poured over powder of myrrh, in the cylinder of the percolator, the fluid which first drops into the receiver is a solution of an oily consistence volume produced by the heat and also the ex- chiefly composed of resin and volatile oil dispansion of the air may burst it. Moreover, solved in alcohol. In like manner when the the process is never so well conducted in a powder of gall-nuts is treated in the same vessel that is too full. way by hydrated sulphuric ether, two layers 41. To obtain Tinctures by Displace- of fluid are obtained, one of which is a highly ment or Percolation. The kind of filtraconcentrated solution of tannin in the water tion commonly called the process of displace- of the ether, and the other a weak solution of ment, for extracting the essence from roots, the same principle in pure ether. In all herbs, seeds, barks, &c., is effected in the cases, therefore, in which it is not otherwise following manner: It is first necessary that directed, it is absolutely necessary to agitate the articles to be acted upon should be ground the several portions of the liquid obtained by percolation together, in order to insure a product of uniform strength, or activity. in a drug mill to the condition of a coarse powder; then weigh each powder by itself, and mix them together in the proportions demanded by the recipe, and moisten the mass thoroughly with alcohol, allowing it to macerate for 12 hours in a vessel well covered.

Next is required a hollow instrument of cylindrical form, having one end shaped liked a funnel, so that it can be inserted in the neck of a glass bottle, and having inside, near the lower end, a partition pierced with numerous small holes, like the strainer of a French coffee-pot, which is a simple coffee percolator; in the absence of such a partition, soft cotton, or any insoluble substance, may be substituted, and being placed in the the inside at the lower end of the instrument, will answer as well as the strainer. This instrument is called a percolator. Boullay's filter or percolator is usually employed. Macerate the ingredients to be acted upon, for the time named-introduce them into the percolator, and slightly press them upon the partition. Any portion of the liquid used in the maceration, not absorbed by the powder, should be poured upon the mass in the instrument, and allowed to percolate. Now gradually pour into the percolator sufficient of the alcohol, or other liquid to be filtered, to drive before it, or displace, the liquid contained in the mass; the portion introduced must in like manner be displaced by another portion; and so on, till the required quantity of filtered liquor is obtained. This extract is called a tincture. In case the liquor which first passes through should be thick and turbid, again introduce it under treatment has become exhausted, the To illustrate the operation of displacement, and describe an excellent percolator for making perfume tinctures, we will suppose that benzoin is under treatment. The apparatus made wholly of glass, having been arranged as shown by the engraving, and a plug of raw cotton dropped loosedly at b, the benzoin in coarse powder is then poured into the tube portion, A, until it Creaches the line, c. Alcohol (95 per cent.) is next added, until it rises to the line, d. As soon as the first portion sinks into the benzoin, a fresh addition must be made; and thus the succeeding relays go on displacing those which preceded them without mingling with them. Each stratum becomes more and more charged with soluble matter as it descends; and when it reaches the bottom of the mass, under the pressure of the superincumbent liquor, it runs out saturated. When, by successive additions of fresh alcohol, the benzoin D B b liquid passes through the mass, and falls | the proportions usually employed for the most into the receiver, B, as tasteless and colorless important perfume tinctures: as when first poured in. This indicates the completion of the process.

Vanilla.

Tincture.

Troy. Alcohol.

Vanilla bean, rasped.....1 lb........8 pts.

Grain musk. .2 drachms.8. pts..

Powder a la frangipani.1 lb.......6 pts.

Rhodium-wood, rasped.1 lb.. .Civet, orris-root. ..2 qts. oz. 2 qts.

Tonka bean. 1 lb. ..8 pts.

Orris-root.

Rhodium As atmospheric pressure is an important Musk.. element in the operation, it will not answer Frangipani to shut it off by closing the top of the dis- Civet... placer, without making some compensating Tonquin arrangement; and, therefore, a communica- Alkanet-red col.. Alkanet.. Orris tion between the upper and lower vessels is Turmeric-yellow.Turmeric.. established by means of a latent-tube arrange- 7 pts... .8 pts. 1 oz 1 qt. 72 oz qt. ment, D. In this manner the apparatus is 43. To Prepare Emulsions. These kept close, and the evaporation of alcohol are milky liquids, formed by the mechanical prevented, while the pressure produced is dis- admixture of oil, balsam, or resin, with water, tributed throughout the apparatus, and ren- by means of some other substance that dered uniform. As the runnings are clear, possesses the property of combining with filtration is rarely necessary. The quantity of both. There are numerous preparations of alcohol thus consumed need not be more than the kind in pharmacy and medicine, which, sufficient to exhaust the material; and the in the later pharmacopœias, have received pharmacopeias, have received resulting tincture must therefore be diluted to the name of "mixtures." There are also the proper strength. For perfumes, deodorized several emulsions employed as cosmetics, as cosmetics, alcohol must always be used.

The method of displacement has the advantage of expedition, economy, and yielding products possessing uniformity of strength; but it requires considerable experience to adapt it to all substances. The art rests in properly packing the ingredients in the cylinder, some substances requiring considerable pressure to be used, while others, when even lightly either alone, or as vehicles for other ingredients. The common name of emulsions is "milk," but the term is often incorrectly extended to opaque white liquids of an en tirely distinct character.

The successful preparation of emulsions is a matter requiring some little skill and care.

In some instances, as with the almond, the two substances necessary to produce a perfect packed, scarcely permit the fluid to pass emulsion are presented by nature, ready to through them. An excellent plan applicable our hand, in the same vegetable production; vegetable production; to all substances, but especially those of a nothing more is necessary than to reduce it with glutinous or mucilaginous nature, is to mix the pestle, and triturate it with water, graduit with water, graduthe powder with an equal bulk of well-washed ally added. In other cases, and which are sand, before rubbing it up with the menstruum. far the more numerous, we have to operate The coarseness of the powder must also be at- on oily or resinous ingredients in their comingredients in their comtended to. Substances that readily become mon form. These we are enabled to suspend soft and pappy when wetted by the menstruum, in water, or mechanically combine with it, by should not be used SO fine as those that are the intervention of thick mucilage, almonds, more woody and fibrous. The method of or yolk of egg. It is found that 1 drachm displacement answers well for the preparation (60 grs.) of the first -made with equal parts of all tinctures that are not of a resinous of good gum-arabic and water (powdered nature, and for most infusions of woody and gum is sometimes used instead of mucilage)fibrous substances, as roots, woods, barks, 1 ounce of the second, (usually about 26 in leaves, seeds, insects, &c. It is especially number), and one of the last, will form 2 adapted for the preparation of concentrated drachms of oil or resinous matter into an infusions and essences, as they may thus be emulsion with about 1 fluid ounce of obtained of any required strength, without water, gradually added; and such an emuladded; and such an emulloss, or requiring concentration by heat, sion, if properly made, will then, in most inproperly made, will then, in most inwhich is so destructive to their virtues. stances, bear further dilution with water.

Ac- When ordinary tinctures are made in large (The yolk of an ordinary-sized hen's egg is requantities, displacement is never likely to su- ferred to. It should be remembered, that persede maceration, on account of any prac-emulsions formed with yolk of egg will not tical advantages it may possess. If the pre- keep long, owing to the putrescible nature scribed directions be duly attended to, the pro- of the latter.) Of these, mucilage is the cess of maceration is unexceptionable. The medium most commonly employed. Accommonly employed. process is more simple than the other; the cording to Montgomery, for conversion into inode of operating more uniform; it is, in fact, permanent emulsions, "oils require about always the same; it requires less of skill and three-fourths their weight balsams and dexterity in conducting it; it requires less spermaceti, equal parts; resins, twice their constant attention during its progress, which, weight; and musk and ambergris 5 times in operating on large quantities, is a considera- its weight." In some cases instead of the tion; and finally, the apparatus required is less above substances, a little liquor of potassa complicated. When, however, only small is employed, when a saponaceous emulsion quantities of tincture are to be made at a time, is formed, which differs considerably in its and kept in stock, the adoption of the process properties from an emulsion of the same of displacement will often be found conve- ingredients produced by means of a bland nient and advantageous. It offers the means of making a tincture in two or three hours, which, by the other process, would require as many weeks. (See No. 4572.) 42. Proportion of Ingredients used for making Tinctures. The following are medium.

In making an emulsion, the gum, or other medium employed, should be first put into the mortar, and rendered thoroughly homogeneous with the pestle. If almonds are used, they should be treated as noticed under "almond-paste" (see No. 1123), a few drops | This is effected by either maceration, percolaof water being added to prevent oiling," and tion, infusion, or decoction, as circumstances to reduce them to a smooth, soft paste. The require: the solution thus obtained is poured oil or resinous matter may then be gradually off and the remaining soluble matter either added and rubbed in, carefully observing not pressed or washed out, and added to the solunot pressed or washed out, and added to the soluto add it more quickly than it can be subdued tion; it is next allowed time to settle, then by the pestle; and if, during this part of the decanted, and strained or filtered; and if this manipulation, the mixture should begin to fails to render the liquid clear, it is clarified exhibit a "breaking" or "curdling" appearance by white of egg, and filtered; Canton flannel, at the edges, a few drops of water must be first soaked in water, being generally emmust be first soaked in water, being generally emimmediately incorporated with it, before add- ployed for this purpose. When water acidadd- ployed for this purpose. When water aciding the remainder of the oil. If this be not ulated with acetic acid is employed, vegetable done. the emulsive mixture in the mortar substances are usually macerated in it in the will, in general, suddenly lose its tenacious cold, or the dilute acid is sprinkled over the consistence, and the process will fail. After bruised plant, if fresh, and the juice expressed the whole of the oil, balsam, or resinous by strong pressure.

When the principles to be extracted are inmatter is thoroughly incorporated, the water or other aqueous vehicle intended to form the soluble, or only slightly soluble, in water , bulk of the emulsion, should be added gradu- alcohol is employed, either in the form of recgradu- alcohol is employed, either in the form of recally and with care, each portion being per- tified spirit, proof spirit, or diluted. These fectly blended with the liquid mass in the produce alcoholic or spirituous extracts; and mortar, by patient trituration, before adding are generally obtained by either maceration or the next. If any alcoholic liquid is employed, it should be added at the very end of the process, and then only very gradually, as otherwise it will cause the separation of the inof the ingredients. It must be observed that soluble salts, spirit, acids, and astringents, are, as a rule, incompatible with the emulsive form. If saline matter must be introduced, it should only be added in a very minute quantity , and in the state of solution, to the readyformed emulsion; and in this case emulsion of alof almonds is the most suitable vehicle. (See No. 1125.) Spirits and acids act by precipitating the mucilaginous matter, or yolk. Even the digestion.

Ether is well adapted for obtaining extracts from bodies whose principles consist of volatile oils or resin, on account of its strong affinity for those substances. Such are termed ethereal extracts. In nearly all cases , filtration is necessary to insure a pure extract.

The means usually employed for evaporating an aqueous solution, are rapid boiling over a fire until the extract is thick enough to offer some risk of burning, and the evaporation finished over a water bath or in shalin shallow vessels at a moderate heat, the further escape of vapor being promoted by continuous stirring with a wooden spoon or stick .

It addition of a very little lemon juice, or of a is not always advisable to heat a solution to portion of slightly acescent syrup, will often the boiling point, but if boiling is resorted to, entirely destroy an emulsion. This inevitably it cannot be done too rapidly, as the heat canit cannot be done too rapidly, as the heat canoccurs with emulsions made with liquor of not rise above its boiling point, and rapid potassa, or other alkaline medium, owing to ebullition hastens evaporation. The fluid must the absolute incompatibility of acids and alkalies in the same liquid.

It is found that volatile oils are more readily made into emulsions if mixed with an equal volume of some simple fixed oil, as that of the almond or olive, before proceeding to operate on them.

All emulsions should be well shaken before use. (Cooley.) never be stirred while ebullition is going on.

Two fundamental rules are:-to conduct evaporation at as low a temperature as is consistent with other objects; and, -to exclude atmospheric air; or, at least, to expose the liquid to its action for as short a time as possible, as most solutions lose more or less of their active principles by heat and exposure.

Solutions which will not bear boiling without loss of strength are evaporated in a vacuum, either in a closed still, or under the receiver of an air pump, in which a vessel is placed containing strong sulphuric acid; this has a the reduction of this solution to a proper por as quickly as it comes in contact with it. A good plan for evaporation, though slow, consistence by evaporation. The substance is first, where practicable, reduced to coarse is to place the liquid in a broad shallow vessel,