mum point is reached, at which the
two liquids distil together without
change in composition. The composi-
tion of an azeotrope depends on the
pressure.
azeotropic distillation A tech-
nique for separating components of
an azeotrope by adding a third liquid
to form a new azeotrope with one of
the original components. It is most
commonly used to separate ethanol
from water, adding benzene to asso-
ciate with the ethanol.
azides Compounds containing the
ion N 3 – or the group –N 3.
azimuthal quantum numberSee
atom.
azine An organic heterocyclic com-
pound containing a six-membered
ring formed from carbon and nitro-
gen atoms. Pyridine is an example
containing one nitrogen atom
(C 5 H 5 N). Diazineshave two nitrogen
atoms in the ring (e.g. C 4 H 4 N 2 ), and
isomers exist depending on the rela-
tive positions of the nitrogen atoms.
Triazines contain three nitrogen
atoms.
A
- Information about IUPAC nomenclature
azo compoundsOrganic com-
pounds containing the group –N=N–
linking two other groups. They can
be formed by reaction of a diazo-
nium ion with a benzene ring.
A- Information about IUPAC nomenclature
azo dyeSee dyes.azoimideSee hydrogen azide.
azulene1.A blue crystalline com-
pound, C 10 H 8 ; m.p. 99°C. It contains a
Üve-membered ring fused to a seven-
membered ring and has aromatic
properties. When heated it is con-
verted into naphthalene. 2.Any of a
number of blue oils that can be pro-
duced by distilling or heating essen-
tial oils from plants.53 azurite
a
123
4 5678AzuleneazuriteA secondary mineral con-
sisting of hydrated basic copper car-
bonate, Cu 3 (OH) 2 (CO 3 ) 2 , in
monoclinic crystalline form. It is
generally formed in the upper zone
of copper ore deposits and often oc-
curs with *malachite. Its intense
azure-blue colour made it formerly
important as a pigment. It is a minor
ore of copper and is used as a gem-
stone.