phur trioxide is dissolved in sul-
phuric acid
H 2 SO 4 + SO 3 →H 2 S 2 O 7
and the oleum is then diluted.continuous phaseSee colloids.continuous spectrumSee spec-
trum.controlled substance In the UK,
an illegal or restricted drug. There
are three classes with different legal
penalties for possession and for deal-
ing.
Class A drugs (the most harmful) in-
clude cocaine, ecstasy, heroin, LSD,
and magic mushrooms. Ampheta-
mines prepared for injection are also
class A drugs.
Class B drugs include amphetamines,
methylphenidate, and pholcodine.
Class C drugs include cannabis,
gammahydroxybutyric acid (GHB),
ketamine, and some painkillers.
Drug use is governed by the Misuse
of Drugs Act, 1971 and 2005. Some
substances fall under the Medicines
Act and are classiÜed as prescription-
only, pharmacist without prescrip-
tion, or generally available.
A- Information about the Misuse of Drugs
Act from the Home OfÜce website
convectionA process by which
heat is transferred from one part of a
Ûuid to another by movement of the
Ûuid itself. In natural convection the
movement occurs as a result of grav-
ity; the hot part of theÛuid expands,
becomes less dense, and is displaced
by the colder denser part of theÛuid
as this drops below it. This is the
process that occurs in most domestic
hot-water systems between the boiler
and the hot-water cylinder. A natural
convection current is set up transfer-
ring the hot water from the boiler up
to the cylinder (always placed above
the boiler) so that the cold waterfrom the cylinder can move down
into the boiler to be heated. In some
modern systems, where small-bore
pipes are used or it is inconvenient to
place the cylinder above the boiler,
the circulation between boiler and
hot-water cylinder relies upon a
pump. This is an example of forced
convection, where hotÛuid is trans-
ferred from one region to another by
a pump or fan.converterThe reaction vessel in
the *Bessemer process or some simi-
lar steel-making process.coomassie blueA biological dye
used for staining proteins.coordinate bond See chemical
bond.coordination compound A com-
pound in which coordinate bonds are
formed (see chemical bond). The
term is used especially for inorganic
*complexes.
A- Information about IUPAC nomenclature
coordination number The num-
ber of groups, molecules, atoms, or
ions surrounding a given atom or ion
in a complex or crystal. For instance,
in a square-planar complex the cen-
tral ion has a coordination number of
four. In a close-packed crystal (see
close packing) the coordination
number is twelve.Cope rearrangement A type of
rearrangement of dienes in which
the position of a substituent changes.
For instance the substituted diene
CH 2 =CH–CH(R)– CH 2 –CH=CH 2 ,
when heated, can convert to
RCH=CH–CH 2 –CH 2 –CH=CH 2.
It involves the formation of a cyclic
transition state, and is an example of
a *sigmatropic reaction.copolymerSee polymer.continuous phase 142c