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177
The Story of Alchemy and the Beginnings of Chemistry
·
M. M. Pattison Muir
136
[9,
10]
Lavoisier
uses
the
word
principle,
here
and
elsewhere,
to
mean
a
definite
homogeneous
substance;
he
uses
it
as
synonymous
with
the
more
modern
terms
element
and
compound.
If
Lavoisier's
memoirs
are
examined
closely,
it
is
seen
that
at
the
very
beginning
of
his
chemical
inquiries
he
assumed
the
accuracy,
and
the
universal
application,
of
the
generalisation
"nothing
is
created,
either
in
the
operations
of
art
or
in
those
of
nature."
Naturalists
had
been
feeling
their
way
for
centuries
towards
such
a
generalisation
as
this;
it
had
been
in
the
air
for
many
generations;
sometimes
it
was
almost
realised
by
this
or
that
investigator,
then
it
escaped
for
long
periods.
Lavoisier
seems
to
have
realised,
by
what
we
call
intuition,
that
however
great
and
astonishing
may
be
the
changes
in
the
properties
of
the
substances
which
mutually
react,
there
is
no
change
in
the
total
quantity
of
material.
Not
only
did
Lavoisier
realise
and
act
on
this
principle,
he
also
measured
quantities
of
substances
by
the
one
practical
method,
namely,
by
weighing;
and
by
doing
this
he
showed
chemists
the
only
road
along
which
they
could
advance
towards
a
genuine
knowledge
of
material
changes.
The
generalisation
expressed
by
Lavoisier
in
the
words
I
have
quoted
is
now
known
as
the
law
of
the
conservation
of
mass;
it
is
generally
stated
in
some
such
form
as
this:--the
sum
of
the
masses
of
all
the
homogeneous
substances
which
take
part
in
a
chemical
(or
physical)
change
does
not
itself
change.
The
science
of
chemistry
rests
on
this
law;
every
quantitative
analysis
assumes
the
accuracy,
and
is
a
proof
of
the
validity,
of
it.[11]
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