b.p. 77.06°C. It is used as a solvent
and inÛavourings and perfumery.
ethyl group The organic group
CH 3 CH 2 –.
ethyl iodide See iodoethane.
ethyne(acetylene)A colourless un-
stable gas, C 2 H 2 , with a characteristic
sweet odour; r.d. 0.618; m.p. –80.8°C;
b.p. –84.0°C. It is the simplest mem-
ber of the *alkyne series of unsatu-
rated hydrocarbons, and is prepared
by the action of water on calcium di-
carbide or by adding alcoholic potas-
sium hydroxide to 1,2-dibromoethane.
It can be manufactured by heating
methane to 1500°C in the presence
of a catalyst. It is used in oxyacety-
lene welding and in the manufacture
of ethanal and ethanoic acid. Ethyne
can be polymerized easily at high
temperatures to give a range of prod-
ucts. The inorganic saltlike dicar-
bides contain the ion C 2 2–, although
ethyne itself is a neutral compound
(i.e. not a protonic acid).
eudiometer An apparatus for
measuring changes in volume of
gases during chemical reactions. A
simple example is a graduated glass
tube sealed at one end and inverted
in mercury. Wires passing into the
tube allow the gas mixture to be
sparked to initiate the reaction be-
tween gases in the tube.
europium Symbol Eu. A soft silvery
metallic element belonging to the
*lanthanoids; a.n. 63; r.a.m. 151.96;
r.d. 5.245 (20°C); m.p. 822°C; b.p.
1597 °C. It occurs in small quantities
in bastanite and monazite. Two sta-
ble isotopes occur naturally: eu-
ropium–151 and europium–153, both
of which are neutron absorbers. Ex-
perimental europium alloys have
been tried for nuclear-reactor parts
but until recently the metal has not
been available in sufÜcient quanti-
ties. It is widely used in the form of
the oxide in phosphors for television
screens. It was discovered by Sir
William Crookes in 1889.
A- Information from the WebElements site
eutectic mixture A solid solution
consisting of two or more substances
and having the lowest freezing point
of any possible mixture of these com-
ponents. The minimum freezing
point for a set of components is
called the eutectic point. Low-
melting-point alloys are usually
eutectic mixtures.Evans balanceSee gouy balance.
evaporationThe change of state
of a liquid into a vapour at a temper-
ature below the boiling point of the
liquid. Evaporation occurs at the sur-
face of a liquid, some of those mol-
ecules with the highest kinetic
energies escaping into the gas phase.
The result is a fall in the average ki-
netic energy of the molecules of the
liquid and consequently a fall in its
temperature.exa-Symbol E. A preÜx used in the
metric system to denote 10^18 times.
For example, 10^18 metres = 1 exame-
tre (Em).EXAFS(extended X-ray absorption
Üne structure) Oscillations of the X-
ray absorption coefÜcient beyond an
absorption edge. The physical cause
of EXAFS is the modiÜcation of the
Ünal state of a photoelectron *wave
function caused by back-scattering
from atoms surrounding the excited
atom. EXAFS is used to determine
structure in chemical, solid state, or
biological systems; it is especially
useful in those systems in which it is
not possible to use diffraction tech-
niques. EXAFS experiments are usu-
ally performed using synchrotron
radiation. It is possible to interpret
EXAFS experiments using single-215 EXAFS
e