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177
The Story of Alchemy and the Beginnings of Chemistry
·
M. M. Pattison Muir
158
Radium
compounds
send
forth
three
kinds
of
rays,
distinguished
as
alpha,
beta,
and
gamma
rays.
Experiments
have
made
it
extremely
probable
that
the
[alpha]-rays
are
streams
of
very
minute
particles,
somewhat
heavier
than
atoms
of
hydrogen,
moving
at
the
rate
of
about
18,000
miles
per
second;
and
that
the
[beta]-rays
are
streams
of
much
more
minute
particles,
the
mass
of
each
of
which
is
about
one
one-thousandth
of
the
mass
of
an
atom
of
hydrogen,
moving
about
ten
times
more
rapidly
than
the
[alpha]-particles,
that
is,
moving
at
the
rate
of
about
180,000
miles
per
second.
The
[gamma]-rays
are
probably
pulsations
of
the
ether,
the
medium
supposed
to
fill
space.
The
emission
of
[alpha]-rays
by
radium
is
accompanied
by
the
production
of
the
inert
elementary
gas,
helium;
therefore,
the
[alpha]-rays
are,
or
quickly
change
into,
rapidly
moving
particles
of
helium.
The
particles
which
constitute
the
[beta]-rays
carry
electric
charges;
these
electrified
particles,
each
approximately
a
thousand
times
lighter
than
an
atom
of
hydrogen,
moving
nearly
as
rapidly
as
the
pulsations
of
the
ether
which
we
call
light,
are
named
electrons.
The
rays
from
radium
compounds
discharge
electrified
bodies,
ionise
gases,
that
is,
cause
them
to
conduct
electricity,
act
on
photographic
plates,
and
produce
profound
changes
in
living
organisms.
The
radium
emanation
is
a
gas
about
111
times
heavier
than
hydrogen;
to
this
gas
Sir
William
Ramsay
has
given
the
name
niton.
The
gas
has
been
condensed
to
a
colourless
liquid,
and
frozen
to
an
opaque
solid
which
glows
like
a
minute
arc-light.
Radium
emanation
gives
off
[alpha]-particles,
that
is,
very
rapidly
moving
atoms
of
helium,
and
deposits
exceedingly
minute
quantities
of
a
solid,
radio-active
substance
known
as
radium
A.
The
change
of
the
emanation
into
helium
and
radium
A
proceeds
fairly
rapidly:
the
half-life
period
of
the
emanation
is
a
little
less
than
four
days.
This
change
is
attended
by
the
liberation
of
much
energy.
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