AmM°ay;imavm-}  Laudanum  Assay.  21 1 
on  the  surface,  until  all  that  is  soluble  is  dissolved.  The  solution  is 
then  filtered  through  a  pair  of  counterbalanced  filters  about  7  cm. 
or  2-8  inches  in  diameter,  the  filters  and  residue  are  well  washed 
first  with  5  cc.  of  lime  water  and  then  with  5  cc.  of  water,  and  when 
drained  they  are  closed  up,  pressed  between  folds  of  bibulous  paper, 
dried  until  they  cease  to  lose  weight  at  1000  C,  and  weighed." 
From  these  data  we  can  easily  calculate  the  percentage  of  insoluble 
matter. 
The  method  used  by  the  writer  for  laudanum  assay  is  as  follows : 
Place  100  cc.  of  the  laudanum  to  be  assayed  into  a  tared  capsule 
of  about  250  cc.  capacity,  evaporate  on  the  water-bath,  occasionally 
stirring,  until  the  contents  of  the  capsule  weighs  about  20  gm., 
while  yet  warm  add  80  cc.  of  cool  distilled  water  slowly,  stirring 
constantly.  Allow  the  capsule  and  contents  to  stand  until  cool  and 
the  insoluble  matter  has  completely  subsided,  then  pour  the  clear 
liquid  on  a  well-wetted  filter  of  about  9  cm.  diameter  so  folded 
that  the  lower  part  of  the  cone  shall  hang  free  from  the  sides  of 
the  funnel.  The  filtrate  is  received  into  a  beaker  marked  at  135  cc. 
After  the  liquid  has  all  been  poured  out  of  the  capsule  about  10  cc. 
of  water  are  added  and  the  residue  removed  from  the  sides  and 
bottom  of  the  capsule  by  means  of  a  rubber  tipped  stirring  rod  and 
transferred  to  the  filter,  two  similar  subsequent  treatments  should 
suffice  to  remove  everything  from  the  capsule  to  the  filter.  If  fil- 
tering is  begun  before  the  insoluble  matter  has  subsided,  it  will  be 
very  tedious  and  unsatisfactory,  for  some  of  the  finer  particles  are 
not  retained  by  the  filter  until  it  is  clogged.  Wash  the  residue  on 
the  filter  well  with  small  portions  of  water,  allowing  each  portion 
to  drain  completely  before  a  subsequent  addition  is  made,  until  the 
residue  is  exhausted  and  the  filtrate  measures  about  135  cc.  Place 
the  filtrate  into  a  tared  capsule  of  about  250  cc.  capacity  and  evap- 
orate on  the  water-bath,  stirring  occasionally,  until  the  filtrate  is 
reduced  to  14  gm.;  while  yet  warm  pour  into  a  tared  flask  of  1 00 
cc.  capacity.  The  portion  remaining  in  the  capsule  is  transferred 
to  the  flask  by  successive  rinsings  of  about  2  cc.  of  water  and 
finally  enough  water  is  added  to  make  the  solution  weigh  20  gm. 
The  precipitating,  separating,  washing  and  drying  is  executed  as  is 
outlined  in  the  Ephemeris  except  that  the  morphine  is  more  thor- 
oughly washed  with  water,  so  that  the  mother  liquor  and  the 
washings  measure  65  cc.  instead  of  50  cc. 
