Cells that contain lignin are fibers, sclerids, vessels, and
tracheids.
limestone A sedimentary rock composed of more
than 50 percent calcium carbonate (CaCO 3 ).
limewater A colorless, somewhat milky, and strongly
alkaline solution of calcium hydroxide produced by
slaking lime.
limiting law An equation that is valid only at very
low concentrations but reflects the correct dependence
upon concentration and charge.
limiting reactant (limiting reagent) In the presence
of two or more reactants in such an amount that a
reaction proceeded to completion, the limiting reactant
would be completely consumed.
linear accelerator A device used for accelerating
charged particles along a straight-line path and often
used in cancer treatment as well as for the study of
nuclear reactions.
linear free-energy relation A linear correlation
between the logarithm of a RATE CONSTANTor equilib-
rium constant for one series of reactions and the loga-
rithm of the rate constant or equilibrium constant for a
related series of reactions. Typical examples of such rela-
tions (also known as linear Gibbs energy relations) are
the BRONSTED RELATION, and the HAMMETT EQUATION.
The name arises because the logarithm of an equi-
librium constant (at constant temperature and pressure)
is proportional to a standard free energy (Gibbs
energy) change, and the logarithm of a rate constant is
a linear function of the free energy (Gibbs energy) of
activation.
The area of physical organic chemistry that deals
with such relations is commonly referred to as linear
free-energy relationships.
See alsoGIBBS ENERGY DIAGRAM; GIBBS ENERGY OF
ACTIVATION; GIBBS FREE ENERGY; STABILITY CONSTANT.
linear Gibbs energy relation See LINEAR FREE-
ENERGY RELATION.linear solvation energy relationships Equations
involving the application of SOLVENT PARAMETERs in
linear or multiple (linear) regression expressing the sol-
vent effect on the rate or equilibrium constant of a
reaction.
See also DIMROTH-REICHARDT ET PARAMETER;
KAMLET-TAFT SOLVENT PARAMETER; KOPPEL-PALM
SOLVENT PARAMETER; STABILITY CONSTANT; Z-VALUE.line formula A two-dimensional representation of
MOLECULAR ENTITIESin which atoms are shown joined
by lines representing single or multiple bonds, without
any indication or implication concerning the spatial
direction of bonds. For example, methanol is repre-
sented as(The term should not be confused with the represen-
tation of chemical formulae by the Wiswesser line nota-
tion, a method of string notation. Formulae in this
notation are also known as “Wiswesser line formulae.”)line-shape analysis Determination of RATE CON-
STANTs for a chemical exchange from the shapes of
spectroscopic lines of dynamic processes. The method
is most often used in NUCLEAR MAGNETIC RESONANCE
SPECTROSCOPY.line spectrum An atomic emission or ABSORPTION
SPECTRUM.Lineweaver-Burk plot See MICHAELIS-MENTEN
KINETICS.linkage isomers An isomer where a specific ligand
bonds to a metal ion through different donor atoms.166 limestone