the Combinations of Phosphorus. 451 
phosphorus, and 2°54, which denotes rather less than half the 
oxygen in phosphorous acid: i. e. as 7°43 to 1*5, an approxi- 
mation nearer than could have been expected. 
Assuming the composition of the phosphuretted gas to be 
what is Stated in the preceding page, which agrees very nearly 
with an experiment which I formerly made, the first experiment 
on the quantity of gas disengaged would give a proportion of 
oxygen rather less than that which has been Just calculated 
upon ; but it must be remembered, that a certain quantity of 
common phosphuretted hydrogen is produced, which contain- 
ing less hydrogen in a given volume, would sufficiently explain 
the difference of result. 
M. Dulong has advanced an ingenious opinion, that the hy- 
pophosphorous acid may be considered as a triple compound of 
hydrogen, oxygen, and phosphorus. There is another view 
which may be taken of its composition, namely, that it may be 
a compound of phosphoric acid and perphosphuretted hydrogen. 
Phosphuretted hydrogen, as may be deduced from some expe- 
riments of M. Dulong, has the properties of a very weak alkali ; 
and when expelled from the neutral hypophosphites, they be- 
come acid. This view agrees very well with the equivalent, or 
proportional numbers, which represent phosphoric acid and 
phosphuretted hydrogen. If it be adopted, the hypophosphites. 
must be considered as triple compounds, analogous to the salts 
containing fixed alkali and earths, or ammonia and earths com- 
bined with acids. 
M. Dulong imagines that the acid formed by the slow com- 
bustion of phosphorus in the air, and which I have supposed to 
be a mixture of phosphorus and phosphoric acids, is a peculiar 
acid, a chemical compound of phosphorous and phosphoric acids, 
which he names phosphatic acid. I cannot say that his argu- 
ments give much probability to this opinion. This substance 
has no crystalline form, no marked character which distinguishes 
it from a mere mixture of phosphorous and phosphoric acids ; 
and as far as my experiments have gone, it is far from uniform 
in its composition ; and phosphorous and phosphoric acids mixed 
together, produce a substance of exactly the same kind. 
That a mixture of phosphorous and phosphoric acids should 
be produced by the slow combustion of phosphorus, is not sur- 
prising, when it is considered that this phenomenon is connected 
with different chemical processes, viz. the action of the vapour 
of phosphorus upon air, the action of solid phosphorus upon the 
elastic atmosphere, and upon the air dissolved in the moisture 
attracted by the acids formed; and, unless vapour be present in 
the air, the process of the slow conversion.of phosphorus into 
acids soon stops. 
‘ Ff2 1 have 
