CONCENTRATIONS
Molal, molar, and normal
solution concentrations are indicated throughout
this Pharmacopeia for most chemical assay and test
procedures (see also Volumetric
Solutions in the section
Reagents, Indicators, and Solutions).
Molality is designated by the symbol
m preceded by a number
that is the number of moles of the designated solute
contained in 1 kilogram of the designated solvent.
Molarity is designated by the symbol M preceded by a
number that is the number of moles of the designated
solute contained in an amount of the designated
solvent that is sufficient to prepare 1 L of
solution. Normality is designated by the symbol N
preceded by a number that is the number of
equivalents of the designated solute contained in an
amount of the designated solvent that is sufficient
to prepare 1 L of solution.
Percentage
Measurements— Percentage concentrations are
expressed as follows:
Percent
Weight in Weight— (w/w) expresses the number
of g of a constituent in 100 g of solution or
mixture.
Percent
Weight in Volume— (w/v) expresses the number
of g of a constituent in 100 mL of solution, and is
used regardless of whether water or another liquid
is the solvent.
Percent
Volume in Volume— (v/v) expresses the number
of mL of a constituent in 100 mL of solution.
The term
percent used
without qualification means, for mixtures of
solids and semisolids, percent weight in
weight; for solutions or suspensions of
solids in liquids, percent weight in volume;
for solutions of liquids in liquids, percent
volume in volume; and for solutions of gases
in liquids, percent weight in volume. For
example,
a 1
percent solution is prepared by dissolving 1
g of a solid or semisolid, or 1 mL of a
liquid, in sufficient solvent to make 100 mL
of the solution.
In the dispensing of
prescription
medications,
slight changes in volume owing to variations
in room temperatures may be disregarded.
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