Dictionary of Chemistry [6th Ed.]

ZrO 2 ) made by fusing ZrO 2 and allow-
ing it to cool under controlled condi-
tions. It is used as an inexpensive
diamond substitute in jewellery.
Often it is erroneously called *zircon.

cumene process An industrial
process for making phenol from ben-
zene. A mixture of benzene vapour
and propene is passed over a phos-
phoric acid catalyst at 250°C and
high pressure

C 6 H 6 + CH 3 CH:CH 2 →

C 6 H 5 CH(CH 3 ) 2

The product is called cumene, and it
can be oxidized in air to a peroxide,
C 6 H 5 C(CH 3 ) 2 O 2 H. This reacts with di-
lute acid to give phenol (C 6 H 5 OH) and
propanone (acetone, CH 3 OCH 3 ),
which is a valuable by-product.

cupellationA method of separat-
ing noble metals (e.g. gold or silver)
from base metals (e.g. lead) by melt-
ing the mixture with a blast of hot
air in a shallow porous dish (the
cupel). The base metals are oxidized,
the oxide being carried away by the
blast of air or absorbed by the porous
container.

cuprammonium ionThe tetraam-
minecopper(II) ion [Cu(NH 3 ) 4 ]2+. See
ammine.

cupric compoundsCompounds
containing copper in its higher (+2)

oxidation state; e.g. cupric chloride is

copper(II) chloride (CuCl 2 ).

cupriteA red mineral cubic form of

copper(I) oxide, Cu 2 O; an important

ore of copper. It occurs where de-

posits of copper have been subjected

to oxidation. The mineral has been

mined as a copper ore in Chile,

Democratic Republic of Congo, Bo-

livia, Australia, Russia, and the USA.

cupronickel A type of corrosion-re-

sistant alloy of copper and nickel

containing up to 45% nickel.

cuprous compounds Compounds

containing copper in its lower (+1)

oxidation state; e.g. cuprous chloride

is copper(I) chloride (CuCl).

curare A resin obtained from the

bark of South American trees of the

genera Strychnos and Chondrodendron

that causes paralysis of voluntary

muscle. It acts by blocking the action

of the neurotransmitter *acetyl-

choline at neuromuscular junctions.

Curare is used as an arrow poison by

South American Indians and was for-

merly used as a muscle relaxant in

surgery.

curieThe former unit of *activity

(see radiation units). It is named

after Marie *Curie.

Curie, Marie(Marya Sklodowska;

1867–1934) Polish-born French

chemist, who went to Paris in 1891.

155 Curie, Marie

c

body-centred simple cubic face-centred

Cubic crystal