Dictionary of Chemistry [6th Ed.]

exist, used as sources of current,

standards of potential, and experi-

mental set-ups for studying electro-

chemical reactions. See also dry cell;

primary cell; secondary cell;

lithium battery.

2.See kerr effect (for Kerr cell).

cellophaneReconstituted cellulose

in the form of a thin transparent

sheet, made by extruding a viscous

cellulose xanthate solution through a

Üne slit into a bath of acid (see

rayon). It is commonly used as a

wrapping material, especially for

foodstuffs, but is being replaced by

polypropene because of itsÛamma-

bility.

cellular plasticSee expanded plas-

tic.

cellular plasticsSolid synthetic

materials having an open structure.

A common example is rigid *poly-

styrene foam used in insulation and

packaging.

celluloidA transparent highly

Ûammable substance made from cel-

lulose nitrate with a camphor plasti-

cizer. It was formerly widely used as

a thermoplastic material, especially

forÜlm (a use now discontinued

owing to theÛammability of cellu-

loid).

celluloseA polysaccharide that

consists of a long unbranched chain

of glucose units. It is the main con-

stituent of the cell walls of all plants,

many algae, and some fungi and is

responsible for providing the rigidity

of the cell wall. It is an important

constituent of dietaryÜbre. The

Übrous nature of extracted cellulose

has led to its use in the textile indus-

try for the production of cotton,

artiÜcial silk, etc.

cellulose acetateSee cellulose

ethanoate.

cellulose ethanoate (cellulose ac-

etate)A compound prepared by

treating cellulose (cotton linters or

wood pulp) with a mixture of

ethanoic anhydride, ethanoic acid,

and concentrated sulphuric acid. Cel-

lulose in the cotton is ethanoylated

and when the resulting solution is

treated with water, cellulose

ethanoate forms as aÛocculent white

mass. It is used in lacquers, nonshat-

terable glass, varnishes, and as aÜbre

(see also rayon).

cellulose nitrateA highlyÛamma-

ble material made by treating cellu-

lose (wood pulp) with concentrated

nitric acid. Despite the alternative

name nitrocellulose, the compound is

in fact an ester (containing CONO 2

groups), not a nitro compound

(which would contain C–NO 2 ). It is

used in explosives (as guncotton) and

celluloid.

Celsius scaleA *temperature scale

in which theÜxed points are the

cellophane 110

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Cellulose