33^ Sir H. Davy's new experiments on some 
as, he says, I have asserted. I cannot find that I have any 
where made such an assertion ; but notwithstanding what 
M. Dulong pretends, the assertion is true, as the follow- 
ing experiment will prove. Half a grain of phosphorus was 
set fire to in a retort containing 1 6 cubical inches of common 
air ; the acid products were washed with distilled water, and 
passed through a filter, and evaporated. When the acid 
became nearly dry, small globules of phosphuretted hydrogen 
were disengaged from it, indicating the presence of phos- 
phorous acid. The experiment was repeated two or three 
times, care being taken to separate the red powder which 
has been considered as an oxide of phosphorus, and always 
with the same result. 
Whenever phosphorus is inflamed, and suffered to become 
extinguished in oxygen gas in excess, unless the product is 
strongly heated after the spontaneous combustion is over, an 
acid , of which the hydrate produces phosphuretted hydrogen 
by heat, is always found in the products ; and this acid is 
probably produced by the action of the solid phosphorus on 
the phosphoric acid in contact with it. This fact, and the 
circumstance, that much phosphorus acid is produced by the 
combustion of phosphorus in rare air, renders it almost cer- 
tain that the phosphorous acid is a direct combination of 
phosphorus and oxygen, and destroys an idea which might 
otherwise be formed from the phenomena of the decompo- 
sition of its hydrate, namely, that it is a compound of three 
proportions of phosphoric acid, and one of phosphuretted 
hydrogen. 
M. Dulong and M. Berzelius s])eak of freeing phospho- 
rane, or the liquid chloride of phosphorus, from phosphorus, 
