chains of atoms in chemical com-
pounds. 2.The formation of a *cate-
nane compound by mechanical
bonding.cathetometerA telescope or
microscopeÜtted with crosswires in
the eyepiece and mounted so that it
can slide along a graduated scale.
Cathetometers are used for accurate
measurement of lengths without me-
chanical contact. The microscope
type is often called a travelling micro-
scope.cathine(β-hydroxyamphetamine)
An alkaloid, C 9 H 13 NO. It may con-
tribute to the stimulant activity of
*khat.cathinone(β-ketoamphetamine)
An alkaloid, C 9 H 11 NO. It is the main
active ingredient in fresh *khat.cathodeA negative electrode. In
*electrolysis cations are attracted to
the cathode. In vacuum electronic de-
vices electrons are emitted by the
cathode andÛow to the *anode. It is
therefore from the cathode that elec-
tronsÛow into these devices. How-
ever, in a primary or secondary cell
the cathode is the electrode that
spontaneously becomes negative dur-
ing discharge, and from which there-
fore electrons emerge.cathodic protection See sacrifi-
cial protection.cationA positively charged ion, i.e.
an ion that is attracted to the cath-
ode in *electrolysis. Compare anion.cationic detergentSee
detergent.cationic dyeSee dyes.cationic resin See ion exchange.causticDescribing a substance that
is strongly alkaline (e.g. caustic soda).caustic potashSee potassium hy-
droxide.caustic sodaSee sodium hydrox-
ide.Cavendish, Henry(1731–1810)
British chemist and physicist, born in
France. Although untrained, his in-
heritance from his grandfather, the
Duke of Devonshire, enabled him to
live as a recluse and study science. In
his experiments with gases (1766), he
correctly distinguished between hy-
drogen and carbon dioxide. In 1784
he showed that sparking mixtures of
hydrogen and oxygen produced pure
water, showing that water is not an
element. Also in sparking experi-
ments with air, Cavendish recog-
nised a small percentage unchanged
(later identiÜed as noble gases).
Cavendish also did signiÜcant work
in physics.c.c.p.Cubic close packing. See close
packing.CDSee circular dichroism.
CD spectrum (circular dichroism
spectrum)The spectrum obtained by
plotting the variable IR– ILagainst
frequency of the incident electro-
magnetic radiation, where IRand ILcathetometer 108c
Cathine