CHAPTER XXXI. SOLID OFFICIAL PREPARATIONS MADE WITHOUT PERCOLATION. IT is not the intention in this chapter to consider in detail the classes of solid official preparations included in the above title, because their manufacture either belongs to the domain of extemporaneous pharmacy or is intimately connected with it. They are more appropriately treated in the final chapters of the work, because their preparation generally demands a higher degree of skill, and a more intimate knowledge of the physical properties of medicinal substances, than are necessary in making those which have been heretofore considered. For these reasons it has been the author's custom, in lecturing upon the subjects treated of in this work, to reserve the consideration of the solid official preparations made without percolation, and those which are embraced under the general term "extemporaneous," until after the student has studied the physical and chemical properties of the various substances which compose the materia medica. It is well for the student to have sufficient knowledge of these preparations to be able to define each class, so that when they are incidentally mentioned in Parts III. and IV. he may be able to describe the use and appearance of a powder, troche, plaster, pill, etc. If it is considered desirable to deviate from this plan, the chapters on these subjects are so constructed that the student may easily turn to them and study them out of the order given here. They will be found in Part VI. It will be well, however, in this place, in order to keep the classification in view, to enumerate them briefly. They are Pills, Troches, Masses, Confections, Powders, Triturations, Suppositories, Cerates, Ointments, Plasters, and Papers. Among those intended for internal administration pills and troches are largely used, and, because their preparation requires the drugs to be in the form of powder, the classes termed powders and triturations, which are dispensed extemporaneously, are grouped with them. Masses and confections are of course considered in connection with pills, because they are used in their preparation. Suppositories stand alone as a class, whilst cerates, ointments, plasters, and papers form a natural group, being preparations that are used externally. PART III. INORGANIC SUBSTANCES. INTRODUCTORY. THE various operations and processes which are used in the practice of pharmacy having been treated of in their general relations to one another in the preceding chapters, it is now necessary to consider in detail the physical and chemical properties of the substances that enter into the preparations which are used in medicine. The plan which will be followed presupposes on the part of the student a knowledge of elementary chemistry, and hence chemical physics, nomenclature, the theoretical construction of formulæ, etc., will not be entered into. The great number of valuable text-books on chemistry, now accessible to every student, renders the introduction of even brief articles on these subjects unnecessary, and the space will be reserved for the consideration of the chemical substances of the materia medica from a pharmaceutical stand-point. For reasons which need not be entered into here, the latest (and to some extent conflicting) views of modern chemists upon the classification of these substances are not adopted, but a method is employed which, whilst it does not do violence to the accepted theories, is simple and practical. The substances are grouped together according to their physical or therapeutical properties, whilst their supposed chemical analogies have not been entirely overlooked. This plan has the merit of giving the student a different view of the chemical substances from that to which he is accustomed in his study of chemistry, and will, perhaps, enhance the interest and impress the points of difference in the substances more forcibly upon the mind. As an illustration, the chemical properties of the non-metallic elements-Hydrogen, Oxygen, and Nitrogen-will not be noticed at length; they are not recognized articles of the materia medica in their free state; but the acids, bases, and salts containing them are largely used, and they form substances which can be advantageously grouped together for profitable study by the pharmacist. The table which follows gives the symbols and atomic weights of the elements; those which are of special interest from a pharmaceutical point of view are distinguished from the rest by being printed in heavier type. The figures given in the last column are those of Meyer and Seubert, and are now official. CHAPTER XXXII. HYDROGEN, OXYGEN, AND WATER. H; 1. 0; 15.96. H2O; 17.96. Hydrogen is a colorless, inodorous, and combustible gas; it is the lightest of all substances. Chemically, it is one of the most important and interesting of the elements, the atomic weights of all being referred to it as unity. Pharmaceutically, in its uncombined state, it is of very little importance, and the reader is referred, for further information, to the chemical text-books. Oxygen, as usually seen, is a colorless, inodorous gas which aids combustion; it is the most abundant of the elements, forming about one-fifth of the total weight of our atmosphere. Water contains nearly ninety per cent. by weight of oxygen, and it is present in varying quantities in most vegetable and animal substances. The compounds which it forms with other bodies are termed oxides: these are of great pharmaceutical interest, and they will be considered hereafter under their appropriate heads. Oxygen in its free, gaseous condition is sometimes used medicinally, but in this state it is of little importance in pharmacy. AQUA. U. S. Water. H2O= 17.96. Natural water in its purest attainable state. Water is the most important and useful compound known to the pharmacist its molecule, H2O, is composed of two parts of hydrogen and one part of oxygen. The purity of water is specified in the official description, which is as follows: TESTS FOR IMPURITIES. The transparency or color of Water should not be affected by hydrogen sulphide T.S. or ammonium sulphide T.S. If 200 C.c. of Water be acidulated with hydrochloric acid and heated to boiling, and 0.5 Gm. of barium chloride T.S. added, the liquid, cooled and filtered, should give no further precipitate on the addition of a few drops of barium chloride T.S., even on standing. It should remain unaffected by mercuric chloride T.S. On evaporating 1000 C.c. of Water on a water-bath, it should not leave a residue weighing more than 0.5 Gm. The above residue, when ignited, should not carbonize. If 200 C.c. of Water be acidulated with nitric acid and 0.5 C.c. of decinormal silver nitrate V.S. be added, the filtered liquid should not be affected by the subsequent addition of a few drops of silver nitrate T.S. Aqua. U. S. IMPURITIES. TESTS FOR IMPURITIES. More than traces Nitrites. Nitrates. On heating 100 C.c. of Water acidulated with 10 C.c. of Uses.-The powers and uses of water as a solvent have been already noticed in the previous chapters. The United States Pharmacopoeia directs water, under the name of Aqua, or distilled water, under the name of Aqua Destillata, to be used in the various processes according to the necessities of the occasion. Ordinary water always contains solid matter and traces of various salts in solution or suspension: these do not unfit it for drinking purposes, but would often seriously interfere with the purity of many chemical substances if such water were used in their preparation. The official processes err on the safe side, and direct distilled water in all cases where the use of ordinary water might be injurious or of doubtful propriety. In some sections of the country the drinking-water might be pure enough for the processes, or at least not contain serious impurities; in other sections the water would be totally unfit for the preparations. The purity of official distilled water is beyond question, and its use therefore removes all doubts. For distilled water the tests for purity are, of course, much more exacting (see below). |