produced is an insoluble substance, whereas the muriatic acid produces a
soluble substance that does not so much thicken the water). And you will
seek out a reason why I take this kind of apparatus for the purpose of
shewing this experiment. I do it because you may repeat in a small way
what I am about to do in a large one. You will have here just the same
kind of action; and I am evolving in this large jar carbonic acid, exactly
the same in its nature and properties as the gas which we obtained from
the combustion of the candle in the atmosphere. And no matter how
different the two methods by which we prepare this carbonic acid, you will
see, when we get to the end of our subject, that it is all exactly the
same, whether prepared in the one way or in the other.
We will now proceed to the next experiment with regard to this gas. What
is its nature? Here is one of the vessels full, and we will try it, as we
have done so many other gases, by combustion. You see it is not
combustible, nor does it support combustion. Neither, as we know, does it
dissolve much in water, because we collect it over water very easily.
Then, you know that it has an effect, and becomes white in contact with
lime-water; and when it does become white in that way, it becomes one of
the constituents to make carbonate of lime or limestone.
The next thing I must shew you is, that it really does dissolve a little
in water, and therefore that it is unlike oxygen and hydrogen in that
respect I have here an apparatus by which we can produce this solution. In
the lower part of this apparatus is marble and acid, and in the upper part
cold water. The valves are so arranged that the gas can get from one to
the other. I will set it in action now, and you can see the gas bubbling
up through the water, as it has been doing all night long, and by this
time we shall find that we have this substance dissolved in the water. If
I take a glass and draw off some of the water, I find that it tastes a
little acid to the mouth: it is impregnated with carbonic acid; and if I
now apply a little lime-water to it, that will give us a test of its
presence. This water will make the lime-water turbid and white, which is
proof of the presence of carbonic acid.
Then it is a very weighty gas it is heavier than the atmosphere. I have
put their respective weights at the lower part of this table, along with,
for comparison, the weights of the other gases we have been examining:
Pint. Cubic Foot.
59