CHAPTER XX WEIGHTS AND MEASURES; ABBREVIATIONS SCALES OF WEIGHTS AND MEASURES APOTHECARIES' WEIGHT The pound (libra) lb. contains 12 ounces. ounce (lutein) 5 " 8 drams, dram (drachma) % " 3 scruples, scruple (scrupulum) 9 " 20 grains, grain (granum) gr. WINE MEASURE The gallon (congius) c contains 8 pints. pint (octa n'us) o " 16 fluidounces. fluidounce (uncia fluidu) f^ " 8 fluidrams. fluidram (drachma fluida) {" " 60 minims. minim (minimim) m - TABLE OF MUTUAL EQUIVALENTS OF WEIGHTS AND MEASURES 12 = 96 = 24 88 = 5760 24 — = 480 3= 6o c o 5 3 m 1 = 8 = 128 = 1024 = 61,440 1= 16= 128= 7,680 1 = 8 = 480 1 = 60 THE METRIC SYSTEM When the metric system is used, the quantities of liquids, as well as solids, are expressed by weight. The gram is the unit of weight, and for practical purposes equals 15 grains. Rule for Converting Troy Weights into Grams. — (a) Reduce each quantity to grains, move the decimal point one place to the left, and subtract one-third. (b) Reduce each quantity to drams and multiply by four. RULE TO REDUCE DOSAGE If quantity in a tablet is greater than required. The given dose is used as the numerator and the required dose as the denominator, thus: The dose of a tablet is marked 1/4 gr., and the required dose is 3-1/2 gr. Therefore, two-thirds of the tablet is the required dose. The tablet should be dissolved in fifteen drops of distilled water and two-thirds, or ten drops, administered as the dose. Rule for Making Solutions of Definite Strengths. — (a) A 1 per cent solution contains 5 grains of the drug to each ounce of the solution. Therefore, a 2 per cent solution contains 10 grains to the ounce; a 5 per cent solution, 25 grains; a 10 per cent solution 50 grains, etc. (b) A 1:1000 solution contains 8 grains to a pint. DOMESTIC MEASURES 1 teaspoonful = 1 dram or 4 cc. 1 dessertspoonful = 2 drams or 8 cc. 1 tablespoonful = 4 drams or 16 cc. 1 wine glass = 2 ounces. 1 tea cup = 5 ounces. 1 tumbler = 11 ounces. TEMPERATURE There are two methods of expressing degrees of heat and cold, Centigrade and Fahrenheit, expressed by the symbols C. and F., respectively. The zero point of the Centigrade scale is the freezing-point of water, equal to 32 °F; and the 100°C point Centigrade is the boiling-point of water, equal to 212°F. Rule for Changing Centigrade Temperatures to Fahrenheit. — Cxo 5 X32 Example : 100 C. (boiling-point of water). C. ioo° x q =qoo / 5 = 180 + 32 = 212°F. To change Fahrenheit to Centigrade : F— 3!2L5_C 0 Example : 212 °F. (boiling-point of water). F. 212° — 32 = 180 X 5 ^=900 / 9 = ioo°C. ABBREVIATIONS aa of each. A. c before meals. Aq water. Aq. bull boiling water. Aq. dest distilled water. Aq. tero hot water. Aq. font spring water. Bene well. B. i. d twice a day. C with. Cc cubic centimeter. Cochl spoonful. Crast tomorrow. D dose. Ft make. Gr grain. Gm gram. Gtt drop. TTL minim. O pint. P. c after meals. P. r. n when necessary. P. i. d every four hours. P. S sufficient quantity. Sine without. Ss one-half. Stat immediately. T. i. d three times a day. Q. i. d four times a day.
Key Takeaways
- Understanding apothecary and metric weights is crucial for accurate dosage in medicine.
- The conversion rules between troy weight and grams are essential for modern pharmacists.
- Domestic measures provide a practical guide to volume equivalents used in home remedies.
Practical Tips
- Use the provided tables to convert between apothecary and metric units accurately.
- When making solutions, always double-check your calculations using the percentage rules given.
- For temperature conversions, remember that 0°C equals 32°F and 100°C equals 212°F.
Warnings & Risks
- Do not confuse apothecary units with metric units when measuring out medications.
- Always use distilled water for dissolving tablets to ensure purity of the dose.
- Be cautious when converting between Fahrenheit and Centigrade; a small error can lead to significant temperature differences.
Modern Application
While this chapter focuses on historical measurement systems used in pharmacy, understanding these units is still valuable today. Accurate dosage conversion remains critical for safe medication use, especially in emergency situations where precise measurements are needed.
Frequently Asked Questions
Q: What is the equivalent of a grain in grams?
The gram is practically equal to 15 grains when using the metric system.
Q: How do you convert troy weights into grams according to this chapter?
To convert troy weights into grams, either reduce each quantity to grains and move the decimal point one place left while subtracting one-third or reduce quantities to drams and multiply by four.
Q: What is a 1:1000 solution in terms of grain concentration?
A 1:1000 solution contains 8 grains of the drug per pint of liquid.