298 Dr. Pe arson's Experiments for 
demonstrated by M. Lavoisier, that charcoal, either totally, 
or a minute proportion excepted, combines with respirable 
air, and forms carbonic acid ; and other familiarly known, 
though less accurate, experiments, show that carbonic acid is 
formed whenever charcoal and respirable air are applied to 
each other in a due degree of heat ; and as there are no other 
sources perceivable of respirable air and charcoal in this ex- 
periment, it seems to prove decisively that they are derived 
from the carbonic acid, which is decompounded by the superior 
affinities between phosphorus and respirable air, and phos- 
phoric acid and alkali, to those between respirable air and 
charcoal, and carbonic acid and alkali. An additional proof 
of the reality of this decomposition is afforded by the exami- 
nation of the 358 grains of white and grey alkaline matter, of 
the same experiment, which afforded much more carbonic acid, 
and much less charcoal and phosphoric acid. I am very fully 
aware that the proportions of respirable air and charcoal, pro- 
duced in this experiment, do not correspond to the proportions 
of them we should have expected, consistently with the syn- 
thetical experiments concerning carbonic acid The variation 
is especially great with respect to respirable air, of which there 
should have been eighteen grains instead of live, to combine 
with the whole of the charcoal, but, from the nature of the 
experiment, we cannot even approximate to the truth with 
respect to the real quantity of respirable air produced ; for the 
phosphorus which sublimed probably carried off a little of this 
air, some of the phosphoric acid thus formed fused along with 
alkali and glass, and some phosphoric selenite remained dis- 
solved in the liquid. Supposing the whole of the charcoal 
formed in this experiment to be united to respirable air, the 
quantity of carbonic acid composed may be calculated to be 104, 
