Apothecary and Household Measurements
LEARNING OBJECTIVES
On completion of the materials provided in this chapter, you will be able to perform computations accurately by mastering the following mathematical concepts:
1 Converting Roman numerals to Arabic numerals
2 Converting Arabic numerals to Roman numerals
3 Adding and subtracting Roman numerals
4 Recalling the apothecary measures of weights and liquids
5 Computing equivalents within the apothecary system by using a proportion
6 Recalling approximate equivalents between apothecary and household measures
7 Computing equivalents between the apothecary and household measurement systems by using a proportion
The apothecary system of measure is a very old English system. It has slowly been replaced by the metric system. When writing orders in the apothecary system, physicians occasionally use Roman numerals. All parts of a whole are expressed as a fraction.
Below is a list of the more commonly used Roman numerals and their Arabic equivalents. Memorize the list.
| Roman numeral | Arabie numeral |
| i | 1 |
| v | 5 |
| x | 10 |
| l | 50 |
| c | 100 |
Only addition and subtraction may be performed in the Roman numeral system.
ADDITION OF ROMAN NUMERALS
SUBTRACTION OF ROMAN NUMERALS
1. Subtraction is performed when a smaller numeral is placed before a larger numeral.
EXAMPLES: ix = 9 iv = 4 ic =99
2. Subtraction is performed when a smaller numeral is placed between two larger numerals. The smaller numeral is subtracted from the larger numeral that follows it.
EXAMPLES: xiv = 14 xxiv = 24 cxc = 190
APOTHECARY MEASUREMENTS
The nurse is already familiar with many of the units of measure in the apothecary system because they are used every day. The nurse most commonly uses the apothecary system units of measure listed in Box 7-1. Memorize all entries in the list.
