Avoirdupois system

The avoirdupois system is also an old system used by the pharmacist, in the past, for ordering bulk chemicals. Since this system is no longer used, practice problems on this topic will not be provided. However, for reference considerations, the following conversions of avoirdupois weights are provided ... 

This amount represents the equivalent of 1 avoirdupois pound. Since the pound is a bulk quantity, use of the avoirdupois system of measurements unit is more common. 

Older units in the metric system and the avoirdupois system are still widely used in the literature, and the information supplied in this appendix is given for convenience in converting these units, Table A-4. 

Avoirdupois is a French word, meaning to weigh. The old English system of weights and measures is referred to as the Avoirdupois System, or U.S. Customary Weights and Measures, to differentiate it from the Metric System. 

An accurate statement of the weight or measure of each component, using the same weight system (metric, avoirdupois, or apothecary) for each component. Reasonable variations may be permitted, however, in the amount of components necessary for the preparation in the dosage form, provided they... 

Certainly in the American-British system there is ample room for confusion. The old question Which is heavier, a pound of feathers or a pound of gold indeed has a catch, one that is not obvious. The pound of feathers is heavier, because gold is measured in troy units in which 1 oz = 3.110 x 10" kg and the feathers are measured in avoirdupois units, in which 1 oz = 2.834 x 10 kg. But the troy pound comprises only 12 rather than 16 oz ... 

The same prefixes are used with mass as with distance, and they have the same meanings. That is one facet that makes the metric system so easy. In the English system, the subdivisions of a yard are a foot—one-third of a yard—and an inch—one-thirty-sixth of a yard. The subdivision of an Avoirdupois pound is an ounce, one-sixteenth of a pound. The subdivision of a Troy pound is an ounce, one-twelfth of that pound. (Gold and silver are measured in Troy ounces.) Each type of measurement has a different subdivision, and none is a multiple of 10. The metric system uses the same prefixes for all types of measurements, they are all multiples of 10, and they always mean the same thing. The symbols for the units and prefixes are easier to learn than those for the English system units. For example, pound is abbreviated lb and ounce is oz, whereas the metric prefixes are almost always closely related to their names. It is easier to convert metric measurements because the prefixes mean some multiple of 10 times the fundamental unit. 

POUND FORCE. The fps system is characterized by a gravitational unit of force, called the pound force (Ib ). The unit is so defined that a standard gravitational field exerts a force of one pound on a mass of one avoirdupois pound. The standard acceleration of free fall in fps units is, to five significant figures,... 

In the cgs system, the standard of mass is the gram and thus the conversion between cgs and mks is a factor of 1000. In the fps system the standard unit of mass is the avoirdupois (which means to have weight in French) with the abbreviation lb (or Ibm—pound-mass), which is derived from the Latin word libra (meaning scale or balance). The factor to convert from pounds to kilograms, by definition, is ... 

In the fps system, the pound force (Ibf) is the quantity measured by an avoirdupois pound at the surface of the earth and is equal to 4.448 N. The Ibf and Ibm are related through the gravitational constant ... 

Avoirdupois (a) weight system Common pound and ounce system where 1 ounce (oz)... 

Grain (gr) (weight) The smallest unit of weight in the Avoirdupois (a) weight system. 

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