LIQUOR  OPII  COMPOSITUS. 
47 
of  the  metrical  or  decimal  system  of  weights  and  measures  are 
also  given  because  they  will  be  found  very  convenient  to  some 
operators,  and  because  it  will  serve  to  familiarize  those  who  read 
them  with  the  values  in  this  system  which  is  coming  into  use. 
Take  of  powdered  opium,  1543  grains  or  100  grammes. 
Stronger  ether. 
Purified  chloroform, 
Acetic  ether, 
Stronger  alcohol, 
Water,  of  each  a  sufiicient  quantity. 
Put  the  powdered  opium  in  a  suitable  vessel  of  not  less  than 
25  fj.  or  750  cc.  (cc.  cubic  centimetre, — 30  cc.  to  the  f^.)  mix 
it  thoroughly  with  20  f^.  or  600  cc.  of  water,  and  allow  the 
mixture  to  macerate  over  night.  The  water  should  be  added  to  the 
powder  in  small  portions  with  active  stirring  until  a  uniform 
smooth  paste  is  made.    The  remainder  is  then  added  at  once 
and  the  whole  well  stirred.    A  strong  stirrer  with  a  spatula- 
shaped,  or   spade-shaped  end  is  almost  indispensable  to  the 
convenient  management  of  this  process  throughout.    It  is  better 
to  use  this  large  proportion  of  water  at  the  outset,  because  it 
enables  the  air  to  separate  easily  and  well  from  the  powder,  and 
thus  much  improves  the  effect  of  the  subsequent  percolations  ; — 
because  it  forms  a  solution  so  dilute  as  not  to  be  precipitated  by 
subsequent  admixture  with  the  weaker  percolates ;  and  because 
it  very  much  facilitates  the  final  exhaustion  of  the  residue.  The 
powder  continues  to  absorb  the  water,  and  the  mixture  to 
diminish  in  volume  for  several  hours  after  the  mixing. 
Take  two  9  inch  or  No.  22  round  filters,  fold  them  separately 
twice  in  the  usual  way  for  plain  filters,  and  open  them  in  the 
usual  way,  with  one  thickness  of  paper  on  one  side  and  three 
thicknesses  on  the  other.  Then  introduce  one  folded  filter  into 
the  other  in  such  a  way  that  the  three  thickness  side  of  each 
shall  coincide  with  the  one  thickness  side  of  the  other.  This 
double  filter  will  then  have  four  thicknesses  of  paper  all  round, 
and  its  eff*ect  in  percolation  is  much  improved  by  conducting  off 
the  liquid  with  uniformity  in  all  directions.  Place  this  double 
filter  not  too  low  down  in  a  5  inch  or  12  centimetre  funnel,  and 
wet  it  well  by  filling  the  filter  and  funnel  with  water  for  a  few 
