Dictionary of Chemistry [6th Ed.]

crystalliteA small crystal, e.g. one

of the small crystals forming part of

a microcrystalline substance.

crystallizationThe process of

forming crystals from a liquid or gas.

crystallographyThe study of crys-

tal form and structure. See also x-ray

crystallography.

crystalloidsSee colloids.

crystal methSee amphetamines.

crystal structure See crystal.

crystal systemA method of classi-

fying crystalline substances on the

basis of their unit cell. There are

seven crystal systems. If the cell is a

parallelopiped with sides a, b, and c

and if αis the angle between b and c,

βthe angle between a and c, and γ

the angle between a and b, the sys-

tems are:

(1) cubica=b=c and α=β=γ=90°

(2) tetragonala=b≠c and α=β=γ=90°

(3) rhombic(or orthorhombic) a≠b≠c

and α=β=γ=90°

(4) hexagonala=b≠c and α=β=γ=90°

(5) trigonala=b≠c and α=β=γ≠ 90 °

(6) monoclinica≠b≠c and α=γ=90°≠β

(7) triclinica=b=c and α≠β≠γ

crystal testA type of *presump-

tive test in which a substance is

identiÜed by the formation of charac-

teristic crystals when a certain

reagent is added. Usually, such tests

are conducted using a microscope

(microcrystal test). An example is the

*acetone–chlor–haemin test for

blood.

CS gasThe vapour from a white

solid, C 6 H 4 (Cl)CH:C(CN) 2 , causing

tears and choking, used in ‘crowd

control’.

cubaneA crystalline hydrocarbon,

C 8 H 8 ; r.d. 1.29; m.p. 131°C. It has a

novel structure with eight carbon

atoms at the corners if a cube, each

attached to a hydrogen. Cubane was

crystallite 154

c

H H

H H

H H

H H

C

C C

C

C

C

C

C

Cubane

Ürst synthesized in 1964 by Philip

Eaton. The C–C–C bond angle of 90°

is highly strained and cubane and its

derivatives have been investigated as

high-energy fuels and explosives. In

particular, octanitrocubane, in which

the hydrogen atoms are replaced by

–NO 2 groups is possibly the most

powerful chemical explosive known,

although, so far, only small amounts

have been synthesized. It decom-

poses to carbon dioxide and nitro-

gen:

C 8 (NO 2 ) 8 →8CO 2 + 4N 2

cubic close packingSee close

packing.

cubic crystalA crystal in which

the unit cell is a cube (see crystal

system). There are three possible

packings for cubic crystals: simple

cubic, face-centred cubic, and body-

centred cubic. See illustration oppo-

site.

A

• An interactive version of a simple cubic
  crystal


• An interactive version of a body-centred
  cubic crystal


• An interactive version of a face-centred
  cubic crystal
  cubic zircona (CZ)A crystal form
  or zircon(IV) oxide (zircon dioxide,