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1036
Enquire within upon everything
·
Robert Kemp Philp
729
Great
care
and
considerable
labour
are
required
in
stirring,
so
that
the
whole
cream
may
be
smoothly
frozen,
and
not
in
hard
lumps.
When
finished,
if
it
is
required
to
be
kept
any
time,
the
melted
ice
and
salt
should
be
allowed
to
escape,
by
removing
the
cork,
and
the
pail
filled
up
with
fresh
materials.
It
is
scarcely
necessary
to
add,
that
if
any
of
the
melted
ice
and
salt
is
allowed
to
mix
with
the
cream,
the
latter
is
spoiled.
From
the
difficulty
of
obtaining
ice
in
places
distant
from
large
towns,
and
in
hot
countries,
and
from
the
impracticability
of
keeping
it
any
length
of
time,
or,
in
fact,
of
keeping
small
quantities
more
than
a
few
hours
its
use
is
much
limited,
and
many
have
been
the
attempts
to
obtain
an
efficient
substitute.
For
this
purpose
various
salts
have
been
employed,
which,
when
dissolved
in
water,
or
in
acids,
absorb
a
sufficient
amount
of
heat
to
freeze
substances
with
which
they
may
be
placed
in
contact.
We
shall
not
attempt,
in
this
article,
to
describe
all
the
various
freezing
mixtures
that
have
been
devised,
but
speak
only
of
those
which
have
been
found
practically
useful.
Many
of
the
freezing
mixtures
which
are
to
be
found
described
in
books
are
incorrectly
so
named,
for
although
they
themselves
are
below
the
freezing
point,
yet
they
are
not
sufficiently
powerful
to
freeze
any
quantity
of
water,
or
other
substances,
when
placed
in
a
vessel
within
them.
In
order
to
be
efficient
as
a
freezing
mixture,
as
distinguished
from
a
cooling
one,
the
materials
used
ought
to
be
capable
of
producing
by
themselves
an
amount
of
cold
more
than
thirty
degrees
below
the
freezing
point
of
water,
and
this
the
ordinary
mixtures
will
not
do.
Much
more
efficient
and
really
freezing
mixtures
may
be
made
by
using
acids
to
dissolve
the
salts.
The
cheapest,
and
perhaps
the
best,
of
these
for
ordinary
use,
is
one
which
is
frequently
employed
in
France,
both
for
making
dessert
ices,
and
cooling
wines,
&c.
It
consists
of
coarsely
powdered
Glauber
salt
(sulphate
of
sodium),
on
which
is
poured
about
two-thirds
its
weight
of
spirit
of
salts
(hydrochloric
acid).
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