Now, having previously arranged an experiment for the purpose of
condensing water from the products of the candle, my next point will be to
shew you this water; and perhaps one of the best means that I can adopt
for shewing its presence to so many at once, is to exhibit a very visible
action of water, and then to apply that test to what is collected as a
drop at the bottom of that vessel. I have here a chemical substance,
discovered by Sir Humphrey Davy, which has a very energetic action upon
water, which I shall use as a test of the presence of water. If I take a
little piece of it--it is called potassium, as coming from potash,--if I
take a little piece of it, and throw it into that basin, you see how it
shews the presence of water by lighting up and floating about, burning
with a violent flame. I am now going to take away the candle which has
been burning beneath the vessel containing ice and salt, and you see a
drop of water--a condensed product of the candle--hanging from under the
surface of the dish.
[Illustration: Fig. 11.]
I will shew you that potassium has the same action upon it as upon the
water in that basin in the experiment we have just tried. See, it takes
fire, and burns in just the same manner. I will take another drop upon
this glass slab, and when I put the potassium on to it, you see at once,
from its taking fire, that there is water present.
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