implosionAn inward collapse of a
vessel, especially as a result of evacu-
ation.IMSSee ion-mobility spectrometry.incandescenceThe emission of
light by a substance as a result of
raising it to a high temperature.InChIA type of *line notation intro-
duced by IUPAC. The acronym stands
for International Chemical IdentiÜer.
Originally, it was IChI (IUPAC chemi-
cal identiÜer). An InChI can give a
large amount of chemical informa-
tion displayed in layers and sublayers
separated by forward slashes. For ex-
ample, the InChI for naphthalene is
InChI=1/C10H8/c-1-2-6-10-8-4-3-7-
9(10)5-1/h1-8H
Here, InChI=1 indicates the version
of InChI used. The remainder of the
string is the main layer. It consists of
three sublayers. These are (1) the mo-
lecular formula (C 10 H 8 ); (2) the atom-
connection information (starting
with c), and (3) the hydrogens pre-
sent (starting with h). Other layers
can be added for such information as
charge, stereochemistry, and isotopic
composition.
A- An FAQ produced by the Chemistry
Department, Cambridge University - Information and downloads from the
IUPAC site
incommensurate latticeA lattice
with long-range periodic order that
has two or more periodicities in
which an irrational number gives the
ratio between the periodicities. An
example of an incommensurate lat-
tice occurs in certain magnetic sys-
tems in which the ratio of the
magnetic period to the atomic lattice
is an irrational number. The phase
transition between a commensurate
lattice and an incommensurate lat-tice can be analysed using the
*Frenkel–Kontorowa model.
indeneA colourlessÛammable hy-
drocarbon, C 9 H 8 ; r.d. 0.996; m.p.
–1.8°C; b.p. 182.6°C. Indene is an
aromatic hydrocarbon with aÜve-
membered ring fused to a benzene
ring. It is present in coal tar and is
used as a solvent and raw material
for making other organic com-
pounds.
independent-particle modelA
model for electrons in a many-
electron system in which the cor-
relation between electrons is either
ignored or taken into account by re-
garding an electron as moving in an
averaged-out potential that repre-
sents the interactions between the
electron and all the other particles in
the system. Although the indepen-
dent-particle model cannot describe
all aspects of many-electron systems,
it had some notable successes, such
as explaining the shell structure of
electrons in atoms.
indeterminacySee uncertainty
principle.
indicatorA substance used to show
the presence of a chemical substance
or ion by its colour. Acid–base indica-
torsare compounds, such as phe-
nolphthalein and methyl orange,
that change colour reversibly, de-
pending on whether the solution is
acidic or basic. They are usually weak
acids in which the un-ionized form
HA has a different colour from the
negative ion A–. In solution the indi-
cator dissociates slightly
HA ˆH++ A–
In acid solution the concentration of
H+is high, and the indicator is
largely undissociated HA; in alkaline
solutions the equilibrium is displaced
to the right and A–is formed. Useful
acid–base indicators show a sharp
colour change over a range of aboutimplosion 282i