NEW  APPARATUS  FOR   RECTIFYING  SPIRITS.  11 
of  the  charging  back  is  opened  just  so  far  as  to  supply  the  still 
with  fresh  spirit,  (along "with  the  returning  weak  spirit,)  at  about 
the  rate  of  the  distillation  of  clean  spirit,  so  that  the  still  may 
be  maintained  at  about  the  same  level.  Then,  if  the  steam  does 
not  vary  much  in  pressure,  it  will  work  very  regularly  for  a  long 
time,  or  until  the  proportion  of  water  to  the  spirit  increases  so 
as  materially  to  raise  the  boiling  point.  The  strength  of  the 
boiling  mixture  is  very  conveniently  indicated  by  the  immersed 
thermometer  inserted  in  the  breast  of  the  still.  At  starting,  the 
boiling  point  of  ordinary  whiskey,  say  "  16  per  cent,  above 
proof,"  is  about  185°,  and  from  this  it  slowly  rises  as  the  spirit 
distills  off,  till  at  the  close  of  the  "  run"  the  charge  is  known  to 
be  exhausted  or  "  spent,"  and  ready  to  discharge  or  "  waste,"  by 
the  indication  of  the  thermometer,  when  the  temperature  ceases 
to  rise.  The  boiling  point  of  the  residuary  liquor,  under  the 
working  pressure  of  the  still,  is  about  216°  to  218°.  Before  dis- 
charging the  spent  liquor  from  the  still,  stopcocks  2  and  4  are 
closed,  and  thus  the  farther  return  of  weak  spirit  is  cut  off  by 
closing  all  communication  with  the  still  till  the  still  is  ready  for 
the  new  charge.  The  large  stopcock,  3,  is  then  opened,  as 
well  as  that  of  the  charging  back,  and  the  still  thus  supplied  with 
a  new  charge  without  arresting  the  process.  Stopcock  1  is 
useful  at  times  during  the  early  part  of  the  run,  in  order  to  run 
a  portion  of  the  return  spirit  in  at  the  upper  part  of  the  column, 
and  thus  to  check  the  rate  of  distillation  while  the  boiling  point 
is  low. 
Under  such  management,  after  a  very  little  practice  and  ob- 
servation, this  apparatus  yields  about  three  barrels  of  clean  pure 
alcohol  a  day,  of  a  strength  varying  in  different  parts  of  the  run- 
ning between  eighty-nine  and  ninety-three  per  cent,  as  indicated 
by  Gay  Lussac's  centesimal  alcoholmeter. 
The  still  being  charged  with  this  clean  pure  alcohol,  and  the 
purifiers  charged  with  chloride  of  calcium  or  quick  lime,  and  a 
new  distillation  made,  a  large  portion  of  the  run  will,  by  careful 
management,  be  found  to  be  absolute  alcohol,  containing  only 
traces  of  the  chloride  of  calcium  or  lime. 
Many  details  of  apparatus  and  management,  as,  for  instance, 
means  and  mode  of  heating  up  the  water  of  the  tubs  at  starting, 
&c,  are  omitted  here  as  unnecessary  to  be  described.    The  en- 
