of Phosphorus and Sulphur, &c. 411 
results of the experiments on the sublimate and the hydrophos- 
phorous acid. 
Unless the product of the combustion of phosphorus is 
strongly heated in oxygene, the quantity of oxygene absorbed 
is less, so that it is probable that phosphorous acid is formed, as 
well as phosphoric acid. 
Phosphorous acid is usually described, in chemical authors, 
as a fluid body, and as formed by the slow combustion of phos- 
phorus in the air; but the liquid so procured is, I find, a solu- 
tion of a mixture of phosphorous and phosphoric acids. And 
the vapour arising from phosphorus in the air at common tem- 
peratures, is a combination of phosphorous acid and the aque- 
ous vapour in the air, and is not, I find, perceived in air artifi- 
cially dried. 
In this case, the phosphorus becomes covered with a white 
film, which appears to be pure phosphorous acid, and it soon 
ceases to shine. 
A solid acid, volatile at a moderate degree of heat, may be 
produced by burning phosphorus in very rare air, and this seems 
to be phosphorous acid free from water ; but some phosphoric 
acid, and some yellow oxide of phosphorus, are always formed 
at the same time. 
The peculiar gas differs exceedingly from phosphoretted hy- 
drogene formed by the action of earths and alkalies and phospho- 
rus upon water; for this last gas is spontaneously inflammable, 
and its specific gravity is seldom more than half as great, and it 
does not afford more than 1.5 its volume of hydrogene when 
decomposed by potassium; it differs in its qualities in different 
cases, and probably consists of different mixtures of hydrogene 
with a peculiar gas, consisting of 3 parts of hydrogene and 
