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Why does the Pharmacopeia direct previous maceration of the powder before percolation ? Because most drugs are not easily extracted by the menstruum, owing to the toughness of the powder, or nature of the desired principles, and maceration secures contact with the solvent for a longer time.
How is this maceration best effected ? By introducing the moistened drug loosely into the percolator, and covering it closely, to prevent loss by evaporation.
How can it be determined if the drug is exhausted ? Only by knowing beforehand what the active principles of the drug are, and testing the percolate, until they are no longer contained therein.
For example : The absence of bitterness in the percolate, from nux vomica, opium, and cinchona, indicates that the bitter alkaloids, to which their activities are due, have been thoroughly extracted from the drug; the absence of color in the percolate of cochineal and saffron, indicates that the desired coloring matters have been exhausted from the drugs, and the absence of astringency in the percolate, of drugs whose activities are due to tannic acid, indicates that it has been completely extracted.
What is the best menstruum for extracting a drug ? The best menstruum for extracting a drug is one that will deprive it of its active and desirable principles, and leave in the residue those principles which are either inert or objectionable.
What other important points are to be taken into consideration in choosing a menstruum ? A menstruum should always be chosen exactly adapted to the characteristics of the drug, and which will cause the retention of the soluble principles in a permanent form under the varying conditions of climate, and at the same time permit exposure to light, heat, and air without injury.
How can this be determined ? Only by experiment.
Can it be accurately predetermined what amount of menstruum a powder will absorb and retain after percolation ceases ? It cannot. The amount varies according to the nature of the drug employed, sometimes as much as eight to twenty per cent.
What great advantage does percolation have over maceration in respect to the character of liquid left in the residue? Maceration leaves a finished tincture in the residue ; in percolation it is merely menstruum, the active portions of the drug having been dissolved in the preceding percolate.
How can absorbed menstrua be recovered ? By distillation, or by treating the residue, first with weak alcohol, then with water.
When water causes a swelling of the substance and stops percolation, what expedients may be resorted to ? Mix the residue with clean sawdust, rice chaff, or other inert dry substances, then percolate with
How may recovered distilled alcohol be purified ? By treating it with permanganate of potassium (12 grains to the gallon), letting it stand a few days, then decanting or filtering.
In conducting the operation of Percolation, how would you control the flow of the Percolate ? By the amount of pressure in packing ; by raising or lowering the receiver containing the nozzle of the delivery
tube, as directed by the U. S. P.; by using a stop-cock (objectionable); or by adopting one of the several forms of percolators devised for that purpose.
Mention some of the special percolators devised as improvements on the ordinary cylindrical and conical percolators, and the principles upon which they are founded. 1. Drusse's glass percolator. In this percolator evaporation is prevented by means of a groundglass cover. The flow of the percolate is checked by screwing in the cover; should it flow too slowly, a piece of twine between the cover and the side will permit the necessary atmospheric pressure.
2. Squibb's Well-tube Percolator. In this percolator a large glass tube, called a well-tube, is placed in the centre of a stone-ware crock and slightly raised from the bottom by absorbent cotton; around it is packed the substance to be percolated, the menstruum is poured on the powder, trickles through and rises in the well, from which it is siphoned.
3. Double-tube Percolator. An ordinary percolator is used. In it is placed a well-tube, with a smaller tube telescoped therein, the end of the latter projecting for a few inches below the percolator through a tightlyfitting cork. The well-tube rests on absorbent cotton. The menstruum percolates through the powder, permeates the cotton, and rises in the welltube to the top of the smaller tube therein, over which it runs into the tube and out, being received in a vessel below. The height of the percolate in the well-tube, and consequently the rapidity of the flow, is controlled by raising or lowering the inner tube.
4. Suspended Percolator (Hance Bros. & White). This percolator is so arranged, being suspended by trunnions from a beam, that it can be readily turned upside down and emptied of its contents. It is suitable for large operations.
How would you support a Percolator ? Several methods are in use; Ist, the ordinary retort stand (flimsy); 2d, Remington's Percolating Stand; this instrument consists of two parallel shelves, one above the other; each shelf consists of two parallel strips having slots down the centre, fastened to which, by thumb-screws working in the slots, are cross-pieces, having their inside edges hollowed out to receive the percolator. The cross-pieces may be slid either way to enlarge or reduce the space between them so as to fit percolators of all sizes. This excellent apparatus is suspended from the wall by brackets. The advantage is that it enables all percolating and filtering operations to be carried on with convenience in one place, thus saving time and labor.
3. Shinn’s Percolating Closet consists of adjustable retort rings sliding up and down on gas-pipe supports, with conveniently arranged shelves, all enclosed in a convenient closet.
What kind of Receiving Bottles should be used for the Percolate ? Wide-mouth bottles are preferred. Where special accuracy is required, use a flask with a double mark on the neck. Bottles may be graduated by pasting a paper slip on the side, pouring in accurately measured quantities of water, carefully marking the height at each addition. A strip of adhesive plaster answers an excellent purpose.
What is meant by Repercolation ? Repercolation is a process introduced by Dr. Squibb, and consists in “ the successive application of the same percolating menstruum to fresh supplies of the substance to be percolated.'
What are its advantages ? By passing the weaker portions of the percolate through fresh portions of drug, it becomes thoroughly saturated. In this way a portion of the percolate will do work as menstruum, resulting in the saving of menstruum.
What is Fractional Percolation ? A term used to define percolation when applied to two successive portions of powder. (Principle identical with repercolation.)
CLASSIFICATION OF OFFICIAL PREPARATIONS.
THE FORMS OF PHARMACEUTICAL PREPARATIONS DIRECTED BY THE UNITED
CLASSIFICATION OF OFFICIAL PREPARATIONS.
AQUÆ-WATERS. Aqua or Water. An aqueous solution of a volatile substance. There are eighteen official waters, three classes, according to their method of preparation. (1) Direct Solution. (2) Filtration through an absorbent powder. (3) Distillation.
THREE CLASSES. (1) DIRECT SOLUTION.—Simple Agitation. Aqua Amygdala Amaræ ; Chloroformi ; Creosoti.
BY DISSOLVING GASES IN COLD WATER.–Aqua Ammoniæ; Ammoniæ Fortior; Chlori ; Hydrogenii Dioxidi.*
(2) FILTRATION THROUGH AN ABSORBENT POWDER.- Aqua Anisi ; Camphoræ ; Cinnamomi; Foeniculi; Mentha Piperitæ, and Menthæ Viridis.. All made by percolation through impregnated Precipitated Calcium Phosphate. In preparing Aqua Camphoræ, a little alcohol is used with the Precipitated Calcium Phosphate, to aid in the trituration of the camphor.
(3) DistilLATION.—Aqua Aurantii Florum Fortior; Aurantii Florum; Rosæ Fortior; Rosæ ; and Aqua Destillata.
Aqua Ammoniæ. Contains 10 p. c. ammonia gas by weight. Externally stimulant, irritant or caustic. Internally antacid and stimulant. Dose 0.6-1.9 C.c. (10 to 30 drops). Should be largely diluted when taken internally. Useful in heartburn, sick headache, syncope. Slowly injected into a vein, a powerful stimulant to heart and respiration.
Aqua Ammoniæ Fortior (Stronger Ammonia Water). Contains 28 p. c. gas by weight. Used for making Aqua Ammonia, or properly diluted (4 or 5 to 8) as a rubefacient, vesicatory, or escharotic. Apply on cotton confined in top of a pill box.
Aqua Amygdalæ Amaræ. (0.2 p. c.). Useful vehicle.
Aqua Aurantii Florum. Prepared by diluting the stronger water with equal volumes distilled water, and is also used as a vehicle.
Aqua Aurantii Florum Fortior (Triple Orange Flower Water). Water saturated with the volatile oil of Fresh Orange Flowers, obtained as a by-product in the distillation of the Oil of Orange Flowers. Vehicle.
Aqua Camphoræ. Camphor 0.8 dissolved in Alcohol and afterward triturated with Precipitated Calcium Phosphate.f Dose 15-30 C.c. (1/2 to i fl. oz.). Vehicle.
Aqua Chlori. Contains 0.4 p. c. chlorine gas. Stimulant and antiseptic. Dose 3.75-15 C.c. (1 to 4 fl. dr.), properly diluted.
Aqua Chloroformi. A saturated solution with excess of Chloroform present. Antiseptic vehicle. Dose 15–60 C.c. (12 to 2 fl. oz.).
Aqua Cinnamomi. Vehicle. Use cautiously in inflamn affections.
* Although H2O2 is not a gas in the usual sense of the term, the solution is classed here for sake of convenience.-(Coblentz.). † Precipitated Calcium Phosphate, U. S. P.