790  Determination  of  Morphine.      '{ Am'NJ0°vur,I^Ih8arm' 
through  a  dry  7  Cm.  paper.  Transfer  50  Cc.  of  the  filtrate  to  an 
evaporating  dish,  and  add  sodium  hydroxide  solution,  drop  by  drop, 
till  the  stirred  liquid  is  just  alkaline  to  litmus  paper.  Add  hydro- 
chloric acid  with  equal  care  till  the  solution  is  acid  once  more,  then 
evaporate  as  rapidly  as  possible  on  the  water  bath  till  the  volume 
of  liquid  remaining  does  not  exceed  5  Cc.  Do  not  evaporate  to 
dryness.  Transfer  the  contents  of  the  dish  to  a  small  separating 
funnel,  washing  the  dish  very  clean  with  alcohol  and  water,  used 
alternately,  and  wiping  it  thoroughly  with  a  rubber-tipped  glass  rod. 
The  total  volume  of  washings  should  not  exceed  15  Cc,  of  which 
not  more  than  5  Cc.  should  be  alcohol.  Add  25  Cc.  of  chloroform- 
alcohol  mixture  (2  volumes  of  chloroform  :  1  volume  of  alcohol)  to 
the  contents  of  the  separating  funnel,  followed  by  a  cold  saturated 
solution  of  sodium  hydrogen  carbonate.  This  latter  should  be 
added  almost  drop  by  drop,  till  complete  alkalinity  is  ensured,  but 
an  undue  excess  must  be  avoided.  An  excess  tends  to  encourage 
emulsification  and  also  unduly  dilutes  the  aqueous  layer  to  be  ex- 
tracted. Shake  the  separating  funnel  well  and  steadily  for  not  less 
than  3  minutes,  then  allow  to  stand.  Separation  into  layers  is  gen- 
erally very  rapid.  Run  the  lower  layer  into  a  flask,  and  repeat  this 
extraction  and  separation,  using  the  same  volume  of  solvent  and 
shaking  for  the  same  period.  Four  such  extractions  should  always 
be  made,  but  if  there  is  any  tendency  to  the  formation  of  an  emul- 
sion a  fifth  extraction  is  desirable  as  a  safeguard.  The  combined 
extracts  are  distilled,  heating  the  flask  on  a  water  bath  almost  to 
dryness.  Dissolve  the  residue  in  an  appropriate  measured  quantity 
of  N/10  sulphuric  acid  or  a  standard  acid  of  approximately  that 
strength  (1  Cc.  acid  =  0.0300  Gm.  morphine  is  very  convenient), 
and  titrate  back  with  N/10  or  N/20  sodium  hydroxide  solution. 
Lacmoid  or  cochineal  are  very  suitable  indicators. 
Qualitative  Examination  of  Titrated  Liquid. — Add  to  the  titrated 
liquid  obtained  as  above  a  drop  of  acid  in  excess,  then  1  Gm.  of 
slaked  lime.  Allow  the  mixture  to  stand  for  a  few  minutes  with 
occasional  shaking,  till  the  lacmoid  has  been  thoroughly  precipi- 
tated. Filter  and  acidify  the  filtrate  slightly  with  hydrochloric 
acid.  Evaporate  on  the  water  bath  to  a  convenient  volume,  and 
apply  any  desired  qualitative  tests  for  the  presence  of  morphine. 
