sign in sign up
<<
Home , Apothecary, Avoirdupois system, Dram (unit), Fluid ounce, Gallon, Grain (unit)

CHAPTER 5

Apothecary and Household and Metric Conversions

LEARNING OBJECTIVES

UNIT 1. List the metric equivalents of 1 fluid , 1 tablespoonful, and 1 tea- OUTLINE spoonful. 2 2. List the metric equivalent of 1 , 1 ounce, and 1 . Introduction 3. Convert a patient’s in pounds to , or in kilograms to pounds. Apothecary of 4. Explain why it is important for technicians to be completely comfortable us- and ing and converting to the . Measures 5. Use to convert between units. Apothecary units Household and Avoirdupois Weights Introduction and Measures Units of weight and In the period of during and after the , the study of and began in earnest. At that in history there was no consistent, in- Measuring doses ternational system of weights and measures. Measurements of (usually re- accurately ferred to as weight) were based on commonly weighed materials, such as a grain Working problems of or a . Different of measurements were used for different using household applications. For example, people who worked in the trades used a different sys- measurements tem of than jewelers or apothecaries. Converting Between The apothecary was a member of the healing arts who was the predecessor of Systems of today’s and a specialist in the preparation of and remedies. Measurement Apothecaries dispensed remedies, performed surgery, or assisted in childbirth. In order to prepare the remedies consistently, apothecaries needed a systematic Conversion factors method for weighing and measuring ingredients. Problems that require conversions between Apothecary System of Weights and Measures systems

Apothecary—A member of the Apothecary units healing arts who was the predeces- sor of today’s . The apothecary system of weights and measures was related to the Roman sys- tem of measurement. This system is based on the grain (abbreviated gr) as a mea- Apothecary System—This surement of weight, and the (fl oz) as a measurement of volume. There are some similarities between apothecary measurements, common house- system is based on the grain as a measurement of weight, and the hold, and avoirdupois measurements (the system of weights and measures his- torically used in the U.S. and Great Britain), but also some significant differences. fluid ounce as a measurement of The apothecary pound, for instance, is divided into 12 , but the avoirdupois volume. pound is divided into 16 ounces. The dry ounce is a measure of weight. To avoid —The confusion, you will learn conversions for ounces and pounds from the household system of weights and measures and avoirdupois only. historically used in the U.S. and Great Britain. 45 CHAPTER 5 | Apothecary and Household Measurements and Metric Conversions 46

The , fluid (fl dr), and fluid ounce are the measurements of volume in the apothecary system. The word “fluid” indicates a measure of volume. Where the apothecary system is used to measure volume, symbols may represent these units. Table 5-1 shows the conversion factors and symbols in the apothecary system.

Table 5-1. Most Likely Measurements a Technician Will Encounter fl ounce fl dram

1 pt 16 fl oz 128 fl dram

1 fl oz 8 fl dram

1 fl dram

Pt = pint, fl = fluid.

Although the apothecary system of measurement was the standard for the practice of into the 20th century in the , it was officially replaced by the metric system in 1971. Use of apothecary measurements is dis- couraged because they are less user-friendly than the metric system, and they are not universally recognized. It is not unheard of, however, for older to write prescriptions using the apothecary system. To be adequately prepared for work in a variety of pharmacy practice settings, students need to be familiar with the more common of the apothecary measurements.

Household and Avoirdupois Weights and Measures

Units of weight and volume Most people who have followed a recipe at home or prepared boxed dinners or desserts are familiar with the household system of measurement. Household mea- surements of weight (mass) are based on the avoirdupois system, which, like the apothecary system is an antiquated system of measurement. The avoirdupois sys- tem is only used to measure weight, and the basic unit is the ounce (oz). House- hold measurements of volume include the (abbreviated tsp), (abbreviated T), fluid ounce, (c), pint (pt), (qt), and (). See Table 5-2.

Table 5-2. Common Household Measurements of Volume and Weight Measurements of Volume 1 gallon 4 8 16 cups 128 fl oz 256 tablesponful (T) 768 tsp 1 quart 2 pints 4 cups 32 fl oz 64 T 192 tsp 1 pint 2 cups 16 fl oz 32 T 96 tsp 1 cup 8 fl oz 16 T 48 tsp 1 fl oz 2 T 6 tsp 1 T 3 tsp Measurements of Weight 1 pound 16 ounces