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62
THE
COMPLETE
PRACTICAL
DISTILLER.
of
B
c,
c
D
is
four
feet,
and
the
capacity
of
the
ba.l
il
is
something
more
than
that
of
the
tube
BCD.
The
distil-
lation
having
commenced,
the
vapours
condensed
will
pass
through
A
and
the
ball
H
into
the
tube
BCD.
But
it
will
only
be
when
the
two
arms
are
filled
that
the
liquor
will
go
out
through
D
to
enter
the
vessel
intended
to
re-
ceive
it.
These two
arms
will
then
remain
filled
during
the
whole
process
of
the
distillation
;
and
in
this
consists
the
remedy
of
the
inconveniences
the
instrument
is
in-
tended
to
remove.
It
is
easy
to
see,
that
if
the
fire
becomes
too
brisk,
the
uncondensed
vapour
will
not
be
able
to
discharge
itself,
by
opening
a
passage
to
the
external
air,
before
having
driven
out
all
the
liquor
contained
in
the
tube
b
c,
and
overcome
the
pressure
of
a
column
the
height
of
which
is
equal
to
c
D.
In
the
second
place,
the
external
air
cannot
enter
to
occupy
the
void
occasioned
by
the
slow-
ness
of
the
fire,
but
only
by
expelling
that
from
D
C,
and
surmounting
a
pressure
of
the
same
height.
Still,
this
column
being
four
feet
in
height,
allows
a
sufficient
lati-
tude
and
time
for
the
workmen
to
regulate
the
fires.
If
the
tube
BCD
was
of
glass,
it
would
only
be
necessary
to
observe
the
level
of
the liquor
in
the
two
arms.
Its
being
lowered
in
b
c
would
indicate
the
necessity
of
diminishing
the
fire
;
and
in
c
D
it
would
be
necessary
to
increase
it.
But
as
the
operation
in
the
tubes
of
this
length
is
rather
precarious,
it
would
be
best
to
attach
to
E
a
little
glass
regulator
E
r
E,
of
which
the
two
arms
E,
F,
each
being
three
inches
long,
contains
mercury
;
this,
in
rising
alternately
in
one
or
the
other,
would
be
an
exact
indication
of
the
degree
of
the
heat,
and
also
of
the
vapours.