What is "empirical formula"

Formula \For"mu*la\, n.; pl. E. Formulas, L. Formul[ae].

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.

   Note: Chemical formul[ae] 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.

Empiric \Em*pir"ic\, Empirical \Em*pir"ic*al\, a.

1. Pertaining to, or founded upon, experiment or experience; depending upon the observation of phenomena; versed in experiments.

   In philosophical language, the term empirical means simply what belongs to or is the product of experience or observation.
   --Sir W. Hamilton.

   The village carpenter . . . lays out his work by empirical rules learnt in his apprenticeship.
   --H. Spencer.

2. Depending upon experience or observation alone, without due regard to science and theory; -- said especially of medical practice, remedies, etc.; wanting in science and deep insight; as, empiric skill, remedies.

   Empirical formula. (Chem.) See under Formula.

   Syn: See Transcendental.

n. (context chemistry English) A notation indicating the ratios of the various elements present in a compound, without regard to the actual numbers.

n. a chemical formula showing the ratio of elements in a compound rather than the total number of atoms

In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, would simply be SO, as is the empirical formula of disulfur dioxide, SO. This means that sulfur monoxide and disulfur dioxide, both compounds of sulfur and oxygen, will have the same empirical formula. However, their chemical formulas, which expresses the number of atoms in each molecule of a chemical compound, will not be the same.

An empirical formula makes no mention of the arrangement or number of atoms. It is standard for many ionic compounds, like calcium chloride (CaCl), and for macromolecules, such as silicon dioxide (SiO).

The molecular formula, on the other hand, shows the number of each type of atom in a molecule. The structural formula shows the arrangement of the molecule. It is also possible for different types of compounds to have equal empirical formulas.