[Sidenote: Relation of chemistry to food science]
If the student is versed in chemistry, this lesson will serve merely
as a review; if not, somewhat close attention must be given to facts
which at first may seem uninteresting. Patience should be exercised,
for, while all the information herein given does not, taken as a whole,
bear directly upon the subjects of health and dis-ease, yet with this
knowledge it will be much less difficult to understand the principles
which are applied later when we take up the chemistry of the body and
the chemistry of food.
Chemistry is not, as popularly supposed, a science far removed from
everyday life. Everyone has some knowledge of chemistry, but the
chemist has observed things more minutely and therefore more accurately
understands the composition of substances and the changes that are
everywhere taking place. For illustration:
A cook starts a fire in a stove. She knows that the fire
must have "air" or it will not burn; that when the fire is first
lighted, it "smokes" heavily, but as it burns more, it smokes less;
further, that if the damper in the pipe is closed the "gas" will
escape in to the room.
[Sidenote: Fire, gas, and smoke the result of chemical changes]
The chemist also knows this, but because he has compared his
observations with similar events elsewhere, he is enabled to express
his knowledge in the language of science. To the chemist, fire is the
process of combustion--the union of the oxygen of the air with the
carbon and hydrogen compounds of the wood or of the coal. The heat of
the fire is generated by this chemical union. To the chemist, the
smoke is a natural phenomenon occasioned by particles of carbon which
fail to unite with the oxygen gas. The gas, which to the woman suggests
suffocation if enough of it escapes into the room, to the chemist
suggests a compound resulting from combination of the oxygen with the
carbon.