combinations of Oxymuriatic Gas and Oxygene , &c. 7 
I have repeated these last operations, in which I conceived 
that prot-oxides were formed. 
Potassium and sodium, when heated in glass tubes in contact 
with about half of their weight of potash and soda, that have 
been ignited, become first of a bright azure, then produce a 
considerable quantity of hydrogene, and at last form a gray 
coherent mass, not fusible at a dull red heat, and which gives 
hydrogene by the action of water. 
Whether these are true prot-oxides, or merely mixtures 
of the alkaline metals with the alkalies, or with the alkalies and 
reduced si-lex from the glass, I shall not at present attempt to 
decide. 
Potassium I find heated in a similar manner with fused 
potash, in a tube of platina, gives after having been ignited, a 
dark mass that effervesces with water ; but even in this case, it 
may be said that the alloy of platina and potassium interferes, 
and that the substance is not a protoxide, but merely dry alkali 
mixed with this alloy. 
As the pure alkalies were unknown, till the discovery of 
potassium and sodium,* and as their properties have never 
been described, it will perhaps be proper in this place to 
notice them briefly. 
* Stahl approached nearly to the discovery of the pure alkalies. He cemented 
solid caustic potash with iron filings in a long continued heat, and states, that in this 
way an alkali “ valde causticum” is produced. Specim . Bech. part ii. page 255. 
He procured caustic alkali also, by decomposing nitre by the metals. Id. p. 253. 
I find that when nitre is decomposed in a crucible of platina, by a strong red heat, 
a yellow substance remains, which consists of potash and oxide of platina, apparently 
in chemical combination. The undecompounded potash w hich comes over in the 
process for procuring potassium by the gun-barrel, is of an olive colour, and affords 
oxide of iron during its solution in water. Pure potash will probably be found to have 
an affinity for many metallic oxides. 
