on the allowed energy levels of the
atom.
Ünger domain AÜnger-shaped
structure produced in a protein when
a series of the constituent amino
acids combines with a metal atom.Üredamp Methane formed in coal
mines.Üre extinguisher A substance that
smothersÛames or prevents their
spreading. Many substances can be
used. Liquids include water, sodium
hydrogencarbonate solution, chlori-
nated organic compounds such as
tetrachloromethane and carbon
dioxide-containing foams. Solid
extinguishers, such as sodium or
potassium hydrogencarbonate, pro-
duce carbon dioxide gas when
strongly heated; solid carbon dioxide
(dry ice) may also be used.Ürst-order reaction See order.
Fischer, Emil Hermann (1852–
1919) German organic chemist who
studied under *Kekulé in Bonn and
later under *Baeyer in Strasbourg.
He moved to Munich in 1875 and
Würzburg in 1885. Fischer is noted
for his extensive pioneering work
on natural products and especially
his work on sugar chemistry. In 1899
he began work on synthesizing pep-
tides and proteins. Fischer was
awarded the 1902 Nobel Prize for
chemistry.
Fischer, Hans (1881–1945) German
organic chemist who worked mainly
in Munich. He worked on por-
phyrins, synthesizing haemin in- Fischer worked also on chloro-
phyll, showing that it was a por-
phyrin containing magnesium. In
1944 he synthesized bilirubin. He
was awarded the 1930 Nobel Prize
for chemistry.
Fischer projection A type of *pro-
jection in which a molecule is drawn
with horizontal bonds representing
bonds coming out of the page and
vertical bonds representing bonds in
the plane of the page or behind the
page. It is named after Emil Fischer.
See absolute configuration.Fischer–Tropsch process An in-
dustrial method of making hydrocar-
bon fuels from carbon monoxide and
hydrogen. The process was invented
in 1933 and used by Germany in
World War II to produce motor fuel.
Hydrogen and carbon monoxide are
mixed in the ratio 2:1 (water gas was
used with added hydrogen) and
passed at 200°C over a nickel or
cobalt catalyst. The resulting hydro-
carbon mixture can be separated into
a higher-boiling fraction for Diesel
engines and a lower-boiling gasoline
fraction. The gasoline fraction con-
tains a high proportion of straight-
chain hydrocarbons and has to be
reformed for use in motor fuel. Alco-
hols, aldehydes, and ketones are also
present. The process is also used in
the manufacture of SNG from coal. It
is named after the German chemist
Franz Fischer (1852–1932) and the
Czech Hans Tropsch (1839–1935).
Üssion-track dating A method of
estimating the age of glass and other
mineral objects by observing the
tracks made in them by theÜssion
fragments of the uranium nuclei that
they contain. By irradiating the ob-
jects with neutrons to induceÜssion
and comparing the density and num-
ber of the tracks before and after ir-
radiation it is possible to estimate the
time that has elapsed since the ob-
ject solidiÜed.
Fittig reaction See wurtz reac-
tion.Üxation See nitrogen fixation.
Üxed point A temperature that
can be accurately reproduced to en-finger domain 226f