C srf 3 
XVIL New experiments on some of the combinations of phosphorus. 
By Sir H. Davy, L.L.D. F. R. S. Vice Pres , R. I. 
Read April g, 1818. 
In a paper published in the Transactions of the Royal Society, 
for 1812, I have detailed a number of experiments on phos- 
phorus, from which I deduced the composition of some of its 
compounds with oxygen, with hydrogen, and with chlorine. 
Since the appearance of this paper, various researches have 
been brought forward on the same subject, in which some 
results, differing very much from each other, and from mine, 
are stated. I ventured to conclude that the phosphoric acid 
contained double the quantity of oxygen to that in the phos- 
phorous acid ; and that phosphoric acid contained about -f of 
its weight of oxygen. 
M. Berzelius considers the oxygen in phosphoric acid to 
be 128.17, and M. Dulong, 124.5, the phosphorus being 100. 
M. Dulong and M. Berzelius suppose the quantity of oxygen 
in phosphorous acid to be to that in phosphoric acid as 3 to 5. 
The motive which immediately induced me to resume the 
enquiry respecting the phosphoric combinations, was M. Du- 
long^s paper. This ingenious chemist has not only endea- 
voured to establish new proportions in the known compounds 
of phosphorus, but has likewise attempted to prove the 
existence of two new acids of phosphorus ; and has denied 
several facts which I considered as sufficiently established. 
The details which I have to lay before the Society in the 
