potassium decompose water? Because it finds oxygen in the water. What is
set free when I put it in the water, as I am about to do again? It sets
free hydrogen, and the hydrogen burns; but the potassium itself combines
with oxygen; and this piece of potassium, in taking the water apart the
water, you may say, derived from the combustion of the candle takes away
the oxygen which the candle took from the air, and so sets the hydrogen
free; and even if I take a piece of ice, and put a piece of potassium upon
it, the beautiful affinities by which the oxygen and the hydrogen are
related are such, that the ice will absolutely set fire to the potassium.
I shew this to you to-day, in order to enlarge your ideas of these things,
and that you may see how greatly results are modified by circumstances.
There is the potassium on the ice, producing a sort of volcanic action.
It will be my place, when next we meet, having pointed out these anomalous
actions, to shew you that none of these extra and strange effects are met
with by us that none of these strange and injurious actions take place
when we are burning, not merely a candle, but gas in our streets, or fuel
in our fireplaces, so long as we confine ourselves within the laws that
Nature has made for our guidance.
LECTURE V.
OXYGEN PRESENT IN THE AIR NATURE OF THE ATMOSPHERE ITS PROPERTIES OTHER
PRODUCTS FROM THE CANDLE CARBONIC ACID ITS PROPERTIES.
We have now seen that we can produce hydrogen and oxygen from the water
that we obtained from the candle. Hydrogen, you know, comes from the
candle, and oxygen, you believe, comes from the air. But then you have a
right to ask me, How is it that the air and the oxygen do not equally
well burn the candle? If you remember what happened when I put a jar of
oxygen over a piece of candle, you recollect there was a very different
kind of combustion to that which took place in the air. Now, why is this?
It is a very important question, and one I shall endeavour to make you
understand: it relates most intimately to the nature of the atmosphere,
and is most important to us.
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