Dictionary of Chemistry [6th Ed.]

able it to be used as the basis of a
*temperature scale.

ÛagpoleSee ring conformations.

ÛameA hot luminous mixture of
gases undergoing combustion. The
chemical reactions in aÛame are
mainly free-radical chain reactions
and the light comes fromÛuores-
cence of excited molecules or ions or
from incandescence of small solid
particles (e.g. carbon).

Ûame testA simple test for met-
als, in which a small amount of the
sample (usually moistened with hy-
drochloric acid) is placed on the end
of a platinum wire and held in a Bun-
senÛame. Certain metals can be de-
tected by the colour produced:
barium (green), calcium (brick red),
lithium (crimson), potassium (lilac),
sodium (yellow), strontium (red).

Ûash photolysisA technique for
studying free-radical reactions in
gases. The apparatus used typically
consists of a long glass or quartz tube
holding the gas, with a lamp outside
the tube suitable for producing an in-
tenseÛash of light. This dissociates
molecules in the sample creating free
radicals, which can be detected spec-
troscopically by a beam of light
passed down the axis of the tube. It is
possible to focus the spectrometer on
an absorption line for a particular
product and measure its change in
intensity with time using an oscillo-
scope. In this way the kinetics of very
fast free-radical gas reactions can be
studied.

Ûash pointThe temperature at
which the vapour above a volatile liq-
uid forms a combustible mixture
with air. At theÛash point the appli-
cation of a nakedÛame gives a mo-
mentaryÛash rather than sustained
combustion, for which the tempera-
ture is too low.

Ûavin adenine dinucleotideSee

fad.

ÛavonesA group of flavanoid com-

pounds found in many plants.

227 flip-flop

f

O

O

Flavone structure

ÛavonoidsA group of naturally oc-

curring phenolic compounds many

of which are plant pigments. They in-

clude the anthocyanins,Ûavonols,

andÛavones.

Ûavoprotein See fad.

Fleming, Sir Alexander

(1881–1955) British bacteriologist,

born in Scotland. He studied medi-

cine at St Mary’s Hospital, London,

where he remained all his life. In

1922 he identiÜed lysozyme, an en-

zyme that destroys bacteria, and in

1928 discovered the antibiotic *peni-

cillin. He shared the 1945 Nobel Prize

for physiology or medicine with *Flo-

rey and *Chain, whoÜrst isolated the

drug.

Ûint(chert)Very hard dense nod-

ules of microcrystalline quartz and

chalcedony found in chalk and lime-

stone.

Ûip-Ûop The movement (transverse

diffusion) of a lipid molecule from

one surface of a *lipid bilayer mem-

brane to the other, which occurs at a

very slow rate. This contrasts with

the much faster rate at which lipid

molecules exchange places with

neighbouring molecules on the same

surface of the membrane (lateral dif-

fusion).