LIQUOR  OPII  COMPOSITUS. 
49 
about  736  grains  or  47'7  grammes.  If  it  be  not  desired  to  weigh 
the  residue  it  is  simply  thrown  away.    If  the  water  bath  be 
well  arranged,  the  evaporation  of  the  percolate  will  be  as  rapid 
as  its  passage  through  the  filter,  even  if  a  pretty  thick  porcelain 
dish  be  used.    But  if  a  tinned  iron  or  tin  capsule  be  used,  the 
rate  of  evaporation  will  exceed  that  of  the  filtration,  and  the 
capsule  will  never  get  more  than  half  full  during  the  process. 
Stirring  is  not  needed  during  the  evaporation.    The  filtration 
and  evaporation  require  from  two  to  three  hours.    When  the 
residue  is  drained  and  disposed  of,  set  the  hot  capsule  and  con- 
tents on  a  scale,  weigh  them  and  subtract  the  tare  of  the  cap- 
sule.   It  will  commonly  happen  that  the  extract  weighs  less 
than  the  original  weight  of  the  powdered  opium  ;   if  so,  add 
water  to  it  until  it  weighs  the  1543  grains  or  100  grammes. 
Then  return  the  capsule  to  the  water  bath  and  warm  the  con- 
tents with  stirring  until  the  whole  of  the  extract  which  has  dried 
upon  the  capsule  is  entirely  redissolved.    Set  the  capsule  on 
the  scale  and  again  add  water  to  make  up  the  loss  by  evapora- 
tion during  this  dissolving  the  extract.    Return  the  capsule  to 
the  water  bath  again,  and  add  to  the  contents  6  f^.  or  180  oc. 
of  stronger  alcohol,  stir   the  mixture  till  it  is  uniform,  and 
heat  it  to  boiling.    Clean  the  vessel  used  for  the  first  mixture  of 
the  opium  and  water,  and  put  into  it  12  fg.  or  360  cc.  af  stron- 
ger alcohol,  and  while  stirring  this  actively  paur  slowly  into  it 
the  contents  of  the  capsule.    Rinse  the  capsule  with  1  fS.  or  30 
cc.  of  stronger  alcohol,  and  add  the  rinsings  to  the  main,  portion.. 
Then  cover  the  vessel  to  prevent  unnecessary  loss  of  alcohol 
by  spontaneous  evaporation,  set  it  aside  for  12.  hours,  or,  over, 
night,  and  then  pour  off  the  clear  alcoholic  solution  from  the  solid . 
tarry  residue.    The  first  portion  of  alcohol  added;  to  the  warm 
watery  extract  in  the  capsule  is  not  suSicien,t  to.  cause  a  precipi- 
tate, but  is  intended  only  to  so  dilute  the  extract  as  to  render 
the  after  precipitation  more  perfect.    The-  pouring,  of  the  con- 
tents of  the  capsule  into  the  alcohoi  causes-  an  immediate  pre- 
cipitation of  a  black  tarry  matter  which  collects  upon  the  stirrer 
and  vessel ;  but  the  solution  does  not  become  clear  at  once^. 
That  is,  the  precipitation  is  not  complete  for  several  hours.  The 
first  extraction  of  the  opium  by  water  rejects  all,  the  solid  mat- 
4 
