of llie combinations of phosphorus. 333 
valent, or proportional numbers, which represent phosphoric 
acid and phosphuretted hydrogen. If it be adopted, the hypo- 
phosphites must be considered as triple compounds, analogous 
to the salts containing fixed alkali and earths, or ammonia 
and earths combined with acids. 
M. Dulong imagines that the acid formed by the slow 
combustion 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 arguments 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 
surprising, 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 phos- 
phorus 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 conver- 
sion of phosphorus into acids soon stops. 
I have mentioned in the paper to which I have referred, in 
the beginning of this communication, that the hydrophospho- 
rous acid is decomposed by heat ; and that phosphoric acid, 
and perphosphuretted hydrogen are the results. In exa- 
mining the nature of the phosphoric acid formed, I find that 
