XXIX. On an easier Mode of procuring Potassium than that 
which is now adopted. By Smithson Tennant, Esq. F. R. S. 
Read June 23, 1814. 
The great discovery of Sir H. Davy, that the alkalies might 
be decomposed by the Voltaic electricity, was soon succeeded 
by that of Gay Lussac and Thenard, who shewed that a 
similar decomposition of them might be produced by means 
of iron. 
Be‘sides the new and unexpected fact which was thus brought 
to light, that the alkaline metals might be deprived of oxygen 
by a substance inferior to them in attraction ; this new pro- 
cess was highly valuable, in affording the means of obtaining 
them far more abundantly than by electricity. 
The circumstances described by Gay Lussac and Thenard, 
as requisite for producing the decomposition of the alkalies by 
iron, are first, that the iron should be intensely heated, and after- 
wards tiiat the alkalies should be brought in contact with it in 
that heated state. For this purpose a furnace must be made, 
capable of admitting a gun barrel, containing the iron turn- 
ings, to pass through it, and a short piece of barrel containing 
the alkali must be adapted to the former by grinding, so as to 
be air tight. As this short piece of barrel is out of the fur- 
nace, G. Lussac and Thenard direct that a separate fire be 
applied to it, in order to make the alkali pass from it into the 
longer barrel. To avoid the necessity of a separate fire, this 
