Once obtained as pure metal, the alkali metals then can be used
as sources of reducing power in other chemical reactions. Sodium
is the usual choice in industry because of its ready availability.
All the alkali metals must be kept away from air and water because
of their strong tendency to return to the +1 oxidation state. Thus
when stored they must be immersed in kerosene or some other organic
liquid. Cesium and rubidium have few uses, the most important being
as electron-releasing metal surfaces in photoelectric devices.
Sodium and potassium ions are important in living organisms. Their
contribution to the composition of a human is shown in the periodic
table on the front end papers.
and help to
keep the proper ionic balance inside and outside cells, so that
the cells do not shrink or swell as their surroundings change in
salt concentration. They also are involved in triggering nerve impulses
down an axon of a neural cell, and hence are critical to the communication
system of the body.
The main positive ion inside cells is ,
in the blood and body fluids outside the cells. The ionic composition
of these body fluids is close to that of sea water diluted with
three volumes of pure water. This is not surprising, in view of
the evolution of life in the oceans. In a sense, our cells have
found a way of carrying around a bit of ocean with them long after
our ancestors left it physically.
The main alkali metal ion in plants is
rather than .
A traditional source of potassium hydroxide, KOH, has been the leaching,
or extraction, of wood ashes with water. The name "potassium" for
the metal comes from the old English term "pot ash" or "cooking
ashes." "Alkali" has the same meaning in Arabic: "al Kali" means
"the ashes." The Arabic word ultimately leads back to the Greek
word for burning, which drifted off in a different direction via
the Latin "caleo," to reach us again in "calorie" and "cauldron."