For"mu*la (?), n.; pl. E.
Formulas (#), L. Formulæ
(#). [L., dim. of forma form, model. SeeForm,
n.] 1. A prescribed or set
form; an established rule; a fixed or conventional method in which
anything is to be done, arranged, or said.
2. (Eccl.) A written confession of
faith; a formal statement of foctrines.
3. (Math.) A rule or principle
expressed in algebraic language; as, the binominal
formula.
4. (Med.) A prescription or recipe for
the preparation of a medicinal compound.
5. (Chem.) A symbolic expression (by
means of letters, figures, etc.) of the constituents or constitution
of a compound.
☞ Chemical formulæ consist of the abbreviations
of the names of the elements, with a small figure at the lower right
hand, to denote the number of atoms of each element contained.
Empirical formula (Chem.), an
expression which gives the simple proportion of the constituents; as,
the empirical formula of acetic acid is
C2H4O2. -- Graphic
formula, Rational formula (Chem.),
an expression of the constitution, and in a limited sense of the
structure, of a compound, by the grouping of its atoms or radicals;
as, a rational formula of acetic acid is
CH3.(C:O).OH; -- called also structural formula,
constitutional formula, etc. See also the formula of
Benzene nucleus, under Benzene. --
Molecular formula (Chem.), a formula
indicating the supposed molecular constitution of a
compound.