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177
The Story of Alchemy and the Beginnings of Chemistry
·
M. M. Pattison Muir
156
Radio-active
substances
are
stores
of
energy,
some
of
which
is
constantly
escaping
from
them;
they
are
constantly
changing
without
external
compulsion,
and
are
constantly
radiating
energy:
all
explosives
are
storehouses
of
energy
which,
or
part
of
which,
can
be
obtained
from
them;
but
the
liberation
of
their
energy
must
be
started
by
some
kind
of
external
shock.
When
an
explosive
substance
has
exploded,
its
existence
as
an
explosive
is
finished;
the
products
of
the
explosion
are
substances
from
which
energy
cannot
be
obtained:
when
a
radio-active
substance
has
exploded,
it
explodes
again,
and
again,
and
again;
a
time
comes,
sooner
or
later,
when
it
has
changed
into
substances
that
are
useless
as
sources
of
energy.
The
disintegration
of
an
explosive,
started
by
an
external
force,
is
generally
completed
in
a
fraction
of
a
second;
change
of
condition
changes
the
rate
of
explosion:
the
"half-life
period"
of
each
radio-active
substance
is
a
constant
characteristic
of
it;
if
a
gram
of
radium
were
kept
for
about
1800
years,
half
of
it
would
have
changed
into
radio-inactive
substances.
Conditions
may
be
arranged
so
that
an
explosive
remains
unchanged--wet
gun-cotton
is
not
exploded
by
a
shock
which
would
start
the
explosion
of
dry
gun-cotton--in
other
words,
the
explosion
of
an
explosive
can
be
regulated:
the
explosive
changes
of
a
radio-active
substance,
which
are
accompanied
by
the
radiation
of
energy,
cannot
be
regulated;
they
proceed
spontaneously
in
a
regular
and
definable
manner
which
is
not
influenced
by
any
external
conditions--such
as
great
change
of
temperature,
presence
or
absence
of
other
substances--so
far
as
these
conditions
have
been
made
the
subject
of
experiment:
the
amount
of
activity
of
a
radio-active
substance
has
not
been
increased
or
diminished
by
any
process
to
which
the
substance
has
been
subjected.
Explosives
are
manufactured
articles;
explosiveness
is
a
property
of
certain
arrangements
of
certain
quantities
of
certain
elements:
so
far
as
experiments
have
gone,
it
has
not
been
found
possible
to
add
the
property
of
radio-activity
to
an
inactive
substance,
or
to
remove
the
property
of
radio-activity
from
an
active
substance;
the
cessation
of
the
radio-activity
of
an
active
substance
is
accompanied
by
the
disappearance
of
the
substance,
and
the
production
of
inactive
bodies
altogether
unlike
the
original
active
body.
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