4 Mr. Davy's Experiments on the 
cases in which I burnt potassium or sodium in common air, 
applying only a gentle heat, I found that the first products 
were substances extremely fusible, and of a reddish brown 
colour, which copiously effervesced in water, and which be- 
came dry alkali, by being strongly heated upon platina in the 
air, phenomena, which, at an early period of the enquiry, in- 
duced me to suppose that they were prot-oxides of potassium 
and sodium. Finding, in subsequent experiments, however, 
that they deflagrated with iron filings, and rapidly oxidated 
platina and silver, I suspended my opinion on the subject, in- 
tending to investigate their nature more fully. 
Since that time, these oxides, as I find by a notice in the 
Moniteur for July 5th, 1810, have occupied the attention of 
M. M.Gay Lussac and Thenard, and these able chemists have 
discovered that they are peroxides of potassium and sodium, 
the one containing, according to them, three times as much 
oxygene as potash, and the other 1.5 times as much as soda 
I have been able to confirm in a general way these interest- 
ing results, though I have not found any means of ascertain- 
ing accurately, the quantity of oxygene contained in these 
new oxides. When they are formed upon metallic sub- 
stances, there is always a considerable oxidation of the metal, 
even though platina be employed. I have used a platina 
tray lined with muriate of potash, that had been fused; but 
in this case, though I am inclined to believe that some alkali 
was formed at the same time with the peroxides, yet I obtained 
an absorpton of 2.6? cubical inches, in a case when 2 grains of 
potassium were employed, and of 1.63 cubical inches, in a case 
when a grain of sodium was used, but in this last instance, the 
edge of the platina tray had been acted upon by the metal. 
