212 Analyses of Books. [Mares, 
sions which I drew from my experiments on phosphuretted 
hydrogen gas, in a paper published in the Aznals of Philosophy, 
viii. 87, or in August, 1816. 
1, Phosphuretted hydrogen gas is composed of one volume of 
hydrogen gas and one volume of vapour of phosphorus condensed 
into one volume, Hence we can ascertam its composition by 
subtracting from the specific gravity of this gas the specific gra- 
vity of hydrogen gas. ; 
2. The specific gravity of phosphuretted hydrogen gas is 
09022; that of hydrogen gas is 0-0694. Hence phosphuretted 
hydrogen gas is composed of 
PLYUFOSED 9) opy.0 eesridig 0:0694 or 1 
Phosphorus ........ 0°8328 12 
3. I consider it as a compound of one atom of hydrogen and 
one atom of phosphorus. On this supposition, an atom of 
phosphorus is 12 times as heavy as an atom of hydrogen ; so that 
if we represent an atom of hydrogen by 0-125, an atom of phos- 
phorus will weigh 1:5 An atom of oxygen weighs 1-000. 
4. One volume of phosphuretted hydrogen gas requires for 
complete combustion either 1 volume or 15 volume of oxygen 
as 
5. In both of these cases, one half volume of the oxygen goes 
to the combustion of the hydrogen. The remainder of the 
oxygen combines with the phosphorus. Thus it appears, that a 
volume of vapour of phosphorus is capable of combining with 
half a volume or with one whole volume of oxygen gas. 
6. I had already shown, in a paper published in the Annals of 
Philosophy, that one volume of vapour of phosphorus is equivalent 
to one atom; and that halfa volume of oxygen gas is equivalent 
to an atom. 
7. Hence it follows that one atom of phosphorus is capable 
of combining with one atom of oxygen or with two atoms of 
oxygen. I concluded, in the paper alluded to, that in the first 
case, phosphorous acid was formed; in the second case, phos- 
phoric acid. Hence it follows, that the constituents of these 
two acids is as follows : 
: Phos, Oxygen. Phos, Oxygen, 
Phosphorous acid....... . 15 + 1 or 100 + 666 
Phosphoric acid. ........ 15 + 2 100 + 1333 
Now according to Davy, the composition of these acids is as 
follows : 
Phos. 
Phosphorous acid...... -. 100 + 67:5 
Phosphoric acid........-. 100 + 135:0 
Thus it appears that Davy’s experiments and mine do not 
differ from each other more than one per cent. As his processes 
