See how the
flame is drawing upwards, presently fading, and at last going out. And
going out, why? Not because it wants air merely, for the jar is as full
now as it was before; but it wants pure, fresh air. The jar is full of
air, partly changed, partly not changed; but it does not contain
sufficient of the fresh air which is necessary for the combustion of a
candle. These are all points which we, as young chemists, have to gather
up; and if we look a little more closely into this kind of action, we
shall find certain steps of reasoning extremely interesting. For instance,
here is the oil-lamp I shewed you--an excellent lamp for our
experiments--the old Argand lamp. I now make it like a candle [obstructing
the passage of air into the centre of the flame]; there is the cotton;
there is the oil rising up it; and there is the conical flame. It burns
poorly, because there is a partial restraint of air. I have allowed no air
to get to it, save round the outside of the flame, and it does not burn
well. I cannot admit more air from the outside, because the wick is large;
but if, as Argand did so cleverly, I open a passage to the middle of the
flame, and so let air come in there, you will see how much more
beautifully it burns. If I shut the air off, look how it smokes; and why?
We have now some very interesting points to study.
Pages:
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43