CONTENTS Metrology. Common system.-Metric system.-Spe- Definitions.-Comminution.-Solution.-Colloidal pension.-Extraction and percolation.-Separation of solids from liquids.Heat.-Sterilization.-Light.-Crystalliza- Liquid preparations for local application. Liniments. Oleates. Petroxolins. - - Powders. Triturations. - Oil sugars. Granular effer- vescing salts. Pills. — Masses. Confections. - Troches. Waters. Infusions. Decoctions. Mucilages. PHARMACY ARITHMETIC OF PHARMACY METROLOGY Definitions. Metrology treats of the measure of length, surface, volume, and weight, and of the relation of one to another. Volume is the amount of space which a body occupies. Weight is the measure of the force with which the earth draws other bodies to its center. Density refers to the weight of a body compared with its volume. Specific gravity is the weight of a body compared with the weight of an equal volume of some substance taken as the standard. COMMON SYSTEM The systems of weights and measures used in the United States are avoirdupois, troy, apothecary, wine, and metric. The avoirdupois weight is used in all commercial transactions where weight is wanted, except in weighing precious stones and in filling prescriptions. Drugs in bulk are bought and sold by the avoirdupois weight even though the bulk is small. An eighth of an ounce of atropine is an eighth of 437.5 grains, not an eighth of 480 grains. This must be kept in mind in pricing prescriptions. Troy weight is used in weighing precious metals and stones. Apothecary weight is used only in filling prescriptions. Apothecary or wine measure is used in measuring fluids. The Imperial measure is used in Great Britain and its provinces. The grain in all systems is the same, so that by going back to it, one system can be converted into another. Attention is called to the variation in the pounds, and particularly to the variation in the ounces. In 1 lb. av. there are 7000 grains, and in 1 lb. apoth. there are 5760 grains. In 1 oz. av. there are 437.5 grains; 1 oz. apoth., 480 grains; I fl. oz. of water, wine measure, 456.3 grains at 4° C. or |