Page 40 - Curriculum Visions Dynamic Book

Potassium
Potassium is found in the sea, in rocks and in plants. It was first obtained from the ashes of plant, as potassium carbonate, known as potash. However, the largest amount of potassium is
in sea water. There is nearly half a kilogram
of potassium oxide in each cubic metre of sea water and much of this can be recovered in
salt pans (along with sodium chloride, common salt) as the water evaporates away. Potassium salts are also found among deposits in desert lakes and in ancient desert rocks.
Potassium is also found in many volcanic rocks. The pink or white feldspar crystals
in granite, for example, are compounds of potassium. In turn, when feldspar weathers to clay, the potassium becomes part of the clay particles that make up the world’s soils.
Potassium compounds
Potassium reacts readily
with the halogens to form potassium halides and with oxygen to form potassium oxide and potassium peroxide.
Potassium is vital to plant growth and large amounts are used in the form of fertilisers such as potassium nitrate and potassium sulphate.
Potassium phosphate
used to be widely used in detergents. However, because the phosphate then found
its way through the sewage systems into rivers and caused water pollution, it is now rarely used for this purpose.
Potassium carbonate (potash) is used in glass-making.
 Potassium salts were traditionally obtained from the ashes of trees and other plants.
The ash yields potassium carbonate contaminated
with a wide variety of other compounds.
Potassium is now recovered from coastal
salt beds at the same time as brine, and also
from underground rock deposits.
40 40