tions or filtrations at the same time, away from the other operations of the shop, in a closet with a closed door. FIG. 333. Receiving Bottles.-A series of bottles of various sizes should be reserved for use in receiving percolates. Where especial accuracy is necessary, a flask with a double mark on the neck should be used (see Fig. 334). Bottles with comparatively wide necks are to be preferred for receiving bottles. A paper strip may be pasted on the side, and accurately measured quantities of water poured in, carefully marking the height of each addition; upon the opposite side corresponding metric quantities may also be placed (see Fig. 335). J. M. Maris & Co. furnish narrow receiving bottles (metric and old form, and both systems on the same bottle) (Fig. 336). The graduations are accurately Percolation closet (Shinn). engraved on the glass, and arranged, at the author's suggestion, to suit the quantities of the U. S. P. 1890. These, unlike the home-made receivers, are permanently marked and of elegant appearance. Repercolation, as its name indicates, is the process of percolating substances with percolates, or, as defined by Dr. E. R. Squibb, the author of the process, "the successive application of the same percolating menstruum to fresh portions of the substance to be percolated." The principal object of repercolation is to effect the saving of alcohol and alcoholic menstrua by accomplishing the saturation of the menstrua, as nearly as possible, by passing the unsaturated or weaker percolate from one portion of the drug through another portion, and again passing the unsaturated or weaker percolate from this second portion through a third portion. The weak percolate from this last portion is generally set aside, to be used in succeeding operations upon the same drug in the place of fresh menstruum. This process is useful only in those operations where the relative proportion of menstruum used is small, as in the fluid extracts and similar concentrated preparations. Practical illustrations of the use of this process may be seen under Fluid Extracts. Fractional Percolation is the term employed by Prof. C. Lewis Diehl and others to define percolation when applied to two successive portions of powder, the principle of action being identical with that of repercolation. QUESTIONS ON CHAPTER XX. PERCOLATION. What is percolation or displacement? What is lixiviation? To whom belongs the credit of first demonstrating the value of the process of percolation in its pharmaceutical applications? What is the principle of action in displacement? What is the instrument used to hold the powder called? What is the liquid poured on the top of the powder called? What is the liquid which passes through the powder called? According to directions given in the U. S. Pharmacopoeia, in what does the process of percolation consist? When the process is successfully conducted, how will the first portion of the percolate compare with the succeeding portions as regards color, odor, etc.? What shape or shapes are most suitable for percolating such quantities as are directed by the U. S. P.? Of what material may it best be constructed? Give the directions for preparing and putting into the percolator a powder for percolation. Give directions for pouring on the menstruum and starting the percolation. How may the flow of the percolate be regulated so as to run with greater or less rapidity? How may a layer of menstruum be kept constantly above the powder, and why is this desirable? In what cases may narrow percolators be advantageously used, and in what cases wide ones? Why is a narrow percolator preferable for making fluid extracts? Upon what depends the proper degree of comminution for a substance to be subjected to percolation? What happens when a powder of unequal degrees of fineness is subjected to percolation? What is the object of moistening a powder before subjecting it to percolation? What is the object of the directions in the U. S. P. given for packing powders in percolation, such as "pack it moderately," "pack it firmly," etc.? In packing a percolator or funnel, how is the powder prevented from running through? How should a powder be packed in a percolator so as to insure its being packed uniformly? After adding a portion of menstruum to a powder in a percolator, should the surface be allowed to become dry, or should the supply of menstruum be continuous? Why? Is maceration previous to percolation desirable? Why? In the process of percolation the direction is often given, "add the menstruum until the substance is exhausted." How may it be known when a drug is exhausted? Give examples. In the choice of menstruums, in what cases would alcohol be indicated? In what cases diluted alcohol? Where would the addition of glycerin be advisable? What advantage has percolation or maceration as regards the absorbed liquid left in the residue? How can alcohol absorbed in residues be recovered? How can the alcohol so recovered be purified? Describe Dursse's percolator, Dr. Squibb's well-tube percolator, the doubletube percolator. What is the object of having a percolator suspended on trunnions? How are percolators ordinarily supported? What is the objection to the ordinary retort-stands? Describe a percolating stand that would be more satisfactory. What is the advantage of a percolating closet. How may receiving bottles be conveniently marked? What is repercolation? What is its principal object? In what operations is repercolation useful? What is fractional percolation? PART II. OFFICIAL PHARMACY. THE various processes which are used in making the official preparations having been considered in Part I., as solution, filtration, digestion, percolation, maceration, expression, etc., it is most appropriate now to take up these preparations and classify them. Those which form natural groups will be brought together in such a manner as to facilitate the study of their general features. Each chapter will begin with a definition and description of the class of preparations treated of; then will follow a table giving a succinct view of the individual preparations forming the class; and after this, the official processes will be found arranged alphabetically. Detailed comments upon the preparations are reserved for the subsequent chapters, the object being at this time to familiarize the student with the various forms of official preparations and fix their general characteristics upon the mind. The following diagram will serve to give a complete view of the classification: it should be carefully examined at the outset, and referred to again after the classes have been studied in detail. 1 Those used internally are in Roman type; those used externally, in Italics. The preparations in this class are mostly extemporaneous, and will be considered under Part V. CHAPTER XXI. AQUEOUS SOLUTIONS. Aquæ. Waters. THE class of preparations termed waters are known also as medicated, aromatic, or distilled waters, and may be simply defined as aqueous solutions of volatile substances. The German Pharmacopoeia and French Codex, however, recognize as waters solutions of non-volatile substances. The volatile substances used in the preparation of waters are either solid, liquid, or gaseous, and the following methods have been employed in effecting their solution: 1. Simple solution in cold water. 2. Solution in hot water. 3. Filtration through an absorbent powder. 4. Percolation through cotton saturated with the substance. 5. Distillation. Most of the medicated waters are used as pleasant vehicles and solvents for the administration of various remedies, and are solutions of aromatic volatile oils. There are eighteen official waters, excluding ordinary water. 1. Simple Solution in Cold Water.-This method is resorted to when the proportion of the volatile substance is small enough to dissolve easily in the quantity of water required. The process where a volatile liquid is the medicating substance is, to agitate it with the water until dissolved, and then to filter the solution. In the case of the gaseous solutions, the gas is passed through the water until a solution of the desired strength is obtained. (See Solution of Gases, p. 205.) Of the eighteen official waters, three are distilled, four are solutions of gases, six are solutions of volatile oils, two are diluted distilled waters, one is a solution of a volatile solid, and two are solutions of volatile liquids. |