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Page 79 text:
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Page 78 text:
Patemal Ancestor of C. W. C. Member of Smokers' Union.
Page 80 text:
Department of Chemistry.
The Ionic Theory and Some of Its Agzpl-ications.
UST a century ago John
Dalton was striving to
prove his famous atomic
theory, which he gave to
XX the scientific world in
1807. To-day Dr. Loeb,
of Chicago University, is
rv working hard, with success
mf? ' - 'ff
' " ' A
seemingly not far distant,
proving his theory of the
ion's relation to life.
Dalton believed that the atom fthe
smallest conceivable division of any
elemcntj has a definite relative weight
as compared with that' of hydrogen,
which he assumes to be 1, and that the
composition of a chemical compound is
constant, that is, that the elements of
which it is composed, always unite in
a definite proportion. To be able to
see clearly the difference between a
compound and an element, a definition
of the terms becomes necessary. An
element is "one of the ultimate, homo-
geneous substances of which anything
is composed," or to make it clearer,
any substance which cannot be divided
into two or- more simpler substances.
A compound is a substance composed
of two or more elements, chemically
Now, as Dalton said, the composi-
tion of a chemical compound is con-
stant. Taking water, HZO, for exam-
ple, which we know is composed of
two parts of hydrogen to one of oxygen,
we find that the smallest conceivable
division of this compound, the mole-
cule, still contains two parts of hydro-
gen to one of ojtygen. These parts
which compose the molecule are atoms.
It has been found that Dalton did not
go quite far enough in his theory of
the atoni-tliat an atom of one element
docs not always replace onek atom of
another element, as he believed, but
may replace several, according to their
respective atomicities or valence. Va-
lence is measured by the power of an
atom to combine with hydrogen. By
hydrochloric acid, HCI, we see that the
valence of the chlorine atom is oneg in
the case of water, HZO, the hydrogen
atom is shown to have a valence of
two, and by carbon dioxide, CO2, the
valence of the carbon atom is proved
to be four, since it combines with two
atoms of oxygen, and we have just
shown the valence of the oxygen atom
to be two. Valence is sometimes repre-
sented by arms or bondsg an atom of
carbon has four arms, an atom of oxy-
gen two, hydrogen 0110, etc. This va-
lence bears a close relation to the ion,
which I shall consider next.
If two salts are mixed together, a re-
action seldom takes place immediate-
ly, or if it does, the action is weak,
but if one or both the salts be in the
form of an aqueous solution, a reaction
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