c. The numbers directly to the right of the terms indicate the conversion between
adjacent units. Notice that the basic difference between the troy and apothecary systems
is the terms employed to subdivide the pound. The troy and apothecary systems are used
very little and restricted to highly specialized fields. The following list of values indicates
the necessity to identify the system of units used for each measurement.
d. If 1 gram is equal to 15.432356 grains as stated, we can check the relationships of the
value listed for the different weight measuring systems. Examples:
(1) In the avoirdupois system, 27.343 grains x 16 grams equals approximately 437
grains per ounce. When you divide 437 grains by 15.432356 (one gram), you find
that 1 avoirdupois ounce is equal to approximately 28.3 grams per ounce.
Multiplying 28.3 grams per ounce by 16 ounces per pound, you find that there are
approximately 453 grams in 1 pound. (AVOIRDUPOIS)
(2) In the troy system, 24 grains x 20 penny weights equals approximately 480
grains per ounce. When you divide 480 grains by 15.432356 grains (one gram),
you find that 1 troy ounce is equal to approximately 31.1 grams per ounce.
Multiplying 31.1 grams per ounce by 12 ounces per pound, you find that there are
approximately 373 grams in one pound. (TROY)
e. For your convenience Table 3 lists conversion factors for most of the common mass
units. You should be able to use the values listed to convert from one system to another.
f. Sensitivity. The sensitivity of a balance is defined as the amount of weight required to
cause a given swing or deflection. This may be stated in various ways. For example, if a
4-mg weight causes the pointer to swing 10 divisions, it may be stated that the balance
has a sensitivity of 0.4 mg per division. Likewise, it might be stated that the balance has a
readability of 1/4 division and a sensitivity of 0.1 mg. In the latter case, the balance has a
detectable sensitivity of 1/4 division or 0.1 mg. If the point were allowed to come to rest,
it would be found that this 4-mg weight only caused a change of 5 divisions in the final
rest point of the pointer from the zero or initial rest point. Now, it should be stated that
the balance has a sensitivity of 0.8 mg per division. You should be aware that there are
different ways to define the term "sensitivity of a balance," but for the purposes of this
course and your calibration program, the sensitivity is the amount of weight required to
change the rest point of the balance one division.