Re: How is potassium obtained or extracted?

Dear User,

K is obtained either directly by electrolysis of K salts or by reaction of 
Na with K salts. K is relatively easy to distill once it has been produced 
by either method, though "crude" commercial potassium is often sold 
directly after electrolysis.

Typical electrolysis reaction would involve:

2K2CO3 ---> 4K + 2CO2 + O2

whereas Na reduction would involve

K2CO3 + 2Na ---> 2K + Na2CO3

Obviously, both processes require inert temperature. Electrolysis requires 
high temperatures, as K salts have to be molten to conduct electricity.

Potash (at least in the textbooks which I have seen) is K2CO3. Old method 
of potash production involved burning seaweed in deep pits, followed by 
extraction of the ashes with hot water and crystallization.

Hope it helps.

A.G.E.

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Admin note:

Martin Thomas adds the following:

As you know, potassium (symbol K) is not found naturally on earth in the
elemental state because the metal is so reactive.  It does occur however
in mineral deposits, chiefly as the chloride  (for example in Stassfurt
near Magdeburg) known as silvine, carnallite ( a hydrated, mixed
potassium-magnesium chloride KCl.MgCl2.6H2O) and as the carbonate,
commonly referred to as potash.


Potassium can be isolated by passing a large electric
current through the carbonate or hydroxide, just as Sir Humphrey
Davy
did when he discovered this element in 1807, when he was just 29 years
old.
You can read his
own
words regarding potassium and its "sister" element sodium, also
discovered by Davy a few days later.



The molten chloride can be reacted with sodium vapor
(sodium metal being more easily obtained) to produce potassium and sodium
chloride.  The potassium is evaporated from the melt and is therefore
obtained in a reasonably pure state by distillation.



Potash can also be smelted with carbon in a manner
analogous to the production of iron.

K2CO3 + 2C = 2K +3CO

A graphic account of this method was given by W.W. Fisher in 1894 in his
Class Book of Elementary Chemistry (2nd edition) Henry Frowde, London &
Macmillan & Co., New York publishers.


"A mixture of potassium carbonate with charcoal is placed in an iron
retort
and brought to an intense red heat in a furnace.  The liberated metal
distils
over as a greenish vapour, and is condensed in flat iron receivers dipping
into naphtha.
   The preparation of the metal is a difficult and somewhat
dangerous
operation owing to the tendancy of the carbonic oxide to unit with it,
thereby forming an explosive substance."




Some notes to leave you with...

Why POTASH?  Well before potassium was discovered the fertilizing
properties of plant ashes was well known.  Plants need various minerals
and so when burnt, their ashes contain those minerals, including
potassium.  The ashes were obtained by burning plants in pots, hence
potash.  Why POTASSIUM?  The name potassium was simply "chemist's Latin"
for the element derived from potash.

Then why the symbol K? K is for Kalium, chemists' Latin as in alkali from
the Arabic alqaliy meaning burnt ashes.


Best regards,

Martin Thomas