The
purification
of
rock
salt
One
of
the
____________________
chemicals
is
salt
(
in
chemical
language
,
sodium
chloride
)
.
This
occurs
in
vast
____________________
in
sea
water
.
It
has
also
been
____________________
on
land
as
a
result
of
the
____________________
of
the
water
from
____________________
which
existed
millions
of
years
ago
.
Rock
salt
is
the
name
given
to
____________________
brown
salt
crystals
which
are
obviously
impure
.
It
is
____________________
out
of
salt
mines
like
those
in
Cheshire
.
It
can
be
purified
in
a
simple
experiment
.
Experiment
Purification
of
rock
salt
1
.
____________________
the
apparatus
for
the
experiment
.
2
.
Take
a
small
amount
of
rock
salt
and
____________________
up
the
crystals
using
a
____________________
and
____________________
.
3
.
Place
a
____________________
of
water
on
a
____________________
on
a
tripod
and
use
a
Bunsen
____________________
to
heat
the
water
until
it
is
warm
.
Pour
the
____________________
crystals
into
the
water
and
____________________
them
until
they
____________________
.
The
solid
brown
dirt
will
not
dissolve
.
4
.
____________________
a
piece
of
filter
paper
and
put
it
in
a
filter
____________________
,
then
mixture
through
the
filter
.
The
brown
dirt
will
remain
on
the
paper
,
while
the
salt
water
will
pass
____________________
it
into
the
basin
.
This
process
is
called
____________________
5
.
Heat
the
____________________
of
salt
water
until
crystals
begin
to
form
at
the
____________________
.
Then
continue
the
evaporation
slowly
using
a
small
____________________
flame
.
Cubic
crystals
of
salt
will
form
.
Before
the
evaporation
is
complete
,
____________________
the
contents
of
the
basin
.
6
.
____________________
the
salt
crystals
with
a
little
cold
water
and
dry
them
with
coarse
filter
paper
or
____________________
paper
.
They
are
now
____________________
salt
.
