Am.  Jour  Pharm. 
May,  1882. 
Opium  Assay. 
249 
filter  the  watery  solution  rapidly,  and  with  some  opiums  very  slowly, 
indeed.  And  when  this  occurs  the  crystals  are  always  darker  and 
more  likely  to  contain  narcotine.  When  the  filtration  is  so  slow  as  to  be 
impracticable,  another  assay  must  be  made  up  to  the  point  of  the  filtra- 
tion. Then  the  filter  must  be  wetted  with  water  instead  of  ether,  and 
the  dark  watery  solution  be  filtered  first.  This  is  easily  done  by  cov- 
ering the  mouth  of  the  flask  with  the  end  of  the  finger  and  slowly 
inverting  the  flask.  The  dark  liquid  will  then  occupy  the  neck  and 
can  be  let  out  slowly  onto  the  filter  to  the  last  drop,  leaving  the  whole 
ethereal  liquid  in  the  flask.  The  operator  should  be  careful  that  no 
crystals  remain  on  his  finger.  When  the  dark  liquid  has  all  passed 
through,  the  filter  should  be  well  washed  with  about  10  cc.  of  water, 
and  be  dried.  Then  the  ethereal  liquid  and  the  remainder  of  the  crys- 
tals should  be  poured  on,  and  the  flasks  be  well  rinsed  with  ether  and 
the  rinsings  be  poured  on  the  filter  with  as  many  of  the  loose  crystals 
as  possible.  The  filter  should  next  be  washed  down  with  5  cc.  of  ether 
and  be  again  dried.  Then  the  flask  should  be  rinsed  out  twice  with  5  cc. 
of  water  each  time  and  the  rinsings  poured  onto  the  filter,  and  the  sides 
be  finally  washed  down  with  water.  It  is  very  difficult  to  dry  a  sub- 
stance completely  in  a  flask  if  there  be  enough  of  the  substance  to  form 
more  than  one  thin  layer  of  particles  at  any  point,  and,  therefore,  as 
few^  crystals  as  possible  should  be  left  in  the  flask.  Usually,  with  good 
management,  the  quantity  is  only  a  few  milligrams.  The  nearer  to  an 
inverted  position  that  a  flask  can  be  placed  without  closing  its  mouth 
too  much,  the  more  quickly  it  will  dry,  because  the  heavier,  moisture- 
charged  air  can  then  continuously  run  out  and  be  replaced  with  dryer 
air.  If  the  flask  be  not  rinsed  out  with  water  last,  a  weighable  quan- 
tity of  ether  residue  will  remain  in  it  with  the  small  quantity  of  mor- 
phia. After  the  filter  has  drained  in  the  funnel,  it  will  still  contain  a 
very  considerable  amount  of  liquid  holding  soluble  matters  which 
should  not  be  dried  w^ith  the  morphia,  hence  the  necessity  of  removing 
it  from  the  funnel,  folding  its  edges  together  as  it  was  before  it  was 
opened,  and  placing  it  between  folds  of  bibulous  paper.  If  a  light 
weight  be  laid  upon  the  folds  of  paper  and  the  filter,  to  keep  a  little 
pressure  upon  them,  the  paper  will  draw  out  as  much  of  the  wash- 
ings as  it  can  hold,  and  thus  not  only  remove  accidental  matters 
in  solution,  but  greatly  facilitate  the  drying  in  a  short  time.  The 
taring  of  the  filter  before  using  is  not  important,  but  is  very  useful  as 
an  indication  of  how  well  the  filter  and  contents  may  have  been  washed, 
for  the  diflerence  in  tare  before  and  after  use  shows  how  nmch  weigh- 
able matter  has  been  left  in  the  paper  when  the  water  was  evaporated 
off,  and  by  inference  how  much  was  left  in  the  morphia,  though  the 
amount  in  the  morphia  is  of  course  much  smaller  than  in  the  paper. 
This  diflerence  in  the  weight  of  the  filter  before  and  after  use,  in  fair 
average  opiums,  will  not  exceed  4  or  5  milligrams,  and  should  never 
exceed  a  centigram.  Adulterated  and  mixed  opiums  usually  give 
greater  differences  and  give  darker  crystals. 
