We show a thermometer; the children are told its use if they are not
already familiar with the instrument; we talk about the quicksilver in the
tube, about its rising or falling according to the degree of heat or cold;
then we inform the class that in some countries where it is very cold
quicksilver freezes; for this reason alcohol, which does not freeze, is
colored red and put into the thermometer tube to be used in these Arctic
regions.
Another use for alcohol is to keep or preserve substances. This we
illustrate by placing a piece of meat into some alcohol. We explain that
the water in the meat is that which causes it to decay. Alcohol has the
power to take up or _absorb_ water; so when meat is put into this liquid
the water from the meat is absorbed by it, and the meat does not become
bad. Those who wish to preserve insects a long time, and doctors who desire
to keep any portion of a human body after death, put these into alcohol, in
which they may be kept for a long time.
Lastly, we let the children smell cologne or other perfumery, and tell them
this is made from different oils mixed with alcohol.
At the close of this lesson the class is ready to help us make the
following BLACKBOARD OUTLINE.
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