the Combinations of Phosphorus. 445 
corrections for the absorption by the water, the apparent absorp- 
tion has been from 35 to 38 cubical inches for every five grains 
of phosphorus. 
M. Dulong’s two methods of ascertaining the quantity of chlo- 
rine in the sublimate, appear to me at least as objectionable as 
his process for determining the composition of phosphoric acid, 
and liable to great errors: the first from the uncertainty of the 
absolute quantity of chlorine admitted; and the second, from the 
loss arising from the vapour of the sublimate, which must be 
carried off by the current of chlorine. How great a deficiency 
may originate from the last circumstance, is shown by the fol- 
lowing experiment. Five grains of phosphorus were converted 
into sublimate by chlorine in great excess, the remaining chlo- 
rine was displaced by passing common air through the vessel for 
some time, till not the slightest smell of chlorine could be per- 
ceived ; the retort was then weighed, and a current of air passed 
through it. Though this current could hardly have replaced the 
air contained in the retort, yet the loss of weight was 1-7 grain, 
and copious vapours were produced in the atmosphere. In a se- 
cond trial of the same kind, there was a greater loss of weight: 
and by barely exhausting the retort, and then again admitting 
air, there was a loss of 7-10ths of a grain. 
When chlorine is made to act upon phosphorus over mercury 
not carefully dried, some muriatic acid gas is always. formed ; 
but when the mercury has been recently boiled, no effect of this 
kind is produced, and the vapour in the gas forms a minute 
quantity of a liquid hydrate of the perchloride, which, by more 
water, is converted into muriatic and phosphoric acids, as | 
proved by some very delicate experiments 5 ; so that there is cer- 
tainly no hydrogen denoted in phosphorus by the action of 
chlorine, and in their mutual action a mere binary compound of 
the two substances is formed. 
After reflecting much upon the methods of combining chlo- 
rine and phosphorus, so as to gain correct results, it occurred to 
me, that in operating over water, and introducing a perfectly 
saturated solution of chlorine to absorb the vapour of the subli- 
mate and of its hydrate formed from the water in the chlorine, 
I should gain a result nearly correct. I made an experiment 
in this way on four grains of phosphorus, ina retort containing 
13 cubical inches. 1 ascertained the absorption, introduced 
into the retort a tube, containing about half a cubical inch of 
saturated solution of chlorine, and suffered the fluid slowly to 
act upon the sublimate, cooling the retort by immersion in 
water; I then ascertained the degree of the second absorption, 
which was nearly a cubical inch and a half. I likewise ascer- 
tained that water had its powers of dissolving chlorine dimi- 
nished, 
