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177
The Story of Alchemy and the Beginnings of Chemistry
·
M. M. Pattison Muir
131
CHAPTER
XII.
THE
RECOGNITION
OF
CHEMICAL
CHANGES
AS
THE
INTERACTIONS
OF
DEFINITE
SUBSTANCES.
The
experimental
study
of
combustion
made
by
Lavoisier
proved
the
correctness
of
that
part
of
Stahl's
phlogistic
theory
which
asserted
that
all
processes
of
combustion
are
very
similar,
but
also
proved
that
this
likeness
consists
in
the
combination
of
a
distinct
gaseous
substance
with
the
material
undergoing
combustion,
and
not
in
the
escape
therefrom
of
the
Principle
of
fire,
as
asserted
by
the
theory
of
Stahl.
After
about
the
year
1790,
it
was
necessary
to
think
of
combustions
in
the
air
as
combinations
of
a
particular
gas,
or
air,
with
the
burning
substances,
or
some
portions
of
them.
This
description
of
processes
of
burning
necessarily
led
to
a
comparison
of
the
gaseous
constituent
of
the
atmosphere
which
played
so
important
a
part
in
these
processes,
with
the
substances
which
were
burned;
it
led
to
the
examination
of
the
compositions
of
many
substances,
and
made
it
necessary
to
devise
a
language
whereby
these
compositions
could
be
stated
clearly
and
consistently.
We
have
seen,
in
former
chapters,
the
extreme
haziness
of
the
alchemical
views
of
composition,
and
the
connexions
between
composition
and
properties.
Although
Boyle[7]
had
stated
very
lucidly
what
he
meant
by
the
composition
of
a
definite
substance,
about
a
century
before
Lavoisier's
work
on
combustion,
nevertheless
the
views
of
chemists
concerning
composition
remained
very
vague
and
incapable
of
definite
expression,
until
the
experimental
investigations
of
Lavoisier
enabled
him
to
form
a
clear
mental
picture
of
chemical
changes
as
interactions
between
definite
quantities
of
distinct
substances.
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