132 Remarks on Priestley’s Analysis 
of carbonic acid which was produced, we can un- 
fortunately do little more than guess. 
In the experiments with needles and iron, carbo- 
nic acid was likewise formed; which appears by the 
crust on the lime-water. Iron, and particularly steel, 
is known to contain carbonaceous matter ;* which, 
combining with some of the oxygen of the air, made 
the carbonic acid. The iron, by losing carbon, must 
have lost weight; but, as the production of car- 
bonic acid seems to have been but small, it is pro- 
bable, that only part of the oxygen, lost in the ope- 
ration, was saturated with carbon; and that the re- 
mainder, combining with the iron, repaired the loss 
of weight of the iron, occasioned by the loss of its 
‘carbonaceous matter, and farther caused the small 
addition to its original weight. t—But I am aware, 
that in following these experiments, which have not 
been made and described with the Doctor’s usual 
care and exactness, I am but groping in the dark ; 
and I hasten to engage the attention of the Society 
to the following experiments on the same subject, 
made by the same able philosopher, and recorded 
in the gd vol. of his Experiments on Air, page 480. 
They are unexceptionable and decisive; and I beg 
leave to recal them to your remembrance, by tran- 
scribing every thing material in them. 
* Plumbago. 
+ There would probably have been nothing equivocal 
in the result of this experiment, if more air or a smaller 
quantity of needles had been employed in it. 
