690 
Determination  of  Morphine. 
Am.  Jour.  Pharm. 
Oct.,  1918. 
medicinal  preparations  may  be  accurately  determined.  This  method, 
or  obvious  modifications  of  it,  has  a  very  wide  range  of  applicability 
— the  more  so,  since  it  calls  for  no  arbitrary  "  corrections,"  but  rests 
on  strictly  stoichiometrical  relations.  It  cannot  be  used,  however, 
when  the  morphine  is  present  in  the  form  of  opium.  To  meet  such 
cases  a  modification  has  been  devised.  This  latter  can  also  be  used 
for  the  examination  of  opium  itself,  and  is  more  accurate  than  the 
methods  at  present  in  use.  As  a  matter  of  convenience  these  will 
be  presented  in  separate  communications. 
Discussion  of  the  Analytical  Data  Obtained. 
Acidimetric  Titration  of  Morphine. — When  morphine  is  dis- 
solved in  standard  sulphuric  acid  and  the  excess  of  acid  is  deter- 
mined by  titration  with  a  caustic  alkali  solution,  the  amount  of  mor- 
phine may  be  calculated  directly  from  its  molecular  weight.  Con- 
trary to  some  statements,  and  to  the  writer's  own  previous  belief, 
it  is  not  necessary  to  standardize  the  acid  on  the  alkaloid  itself. 
Some  of  the  writer's  earlier  experiments  did  not  bear  out  this  view, 
but  it  was  later  found  that  the  acid  used  had  been  standardized  by 
a  faulty  method.  By  Experiment  1  (see  subsequent  pages)  it  is 
shown  that  1  Cc.  ^  H2S04  =  0.0304  Gm.  C17H19N03-H20  and 
while  theory  calls  for  less  by  0.0001  Gm.,  the  difference  is  within 
the  limit  of  observational  error,  so  that  the  theoretical  figure  0.0303 
should  be  used.  That  methyl  orange  gives  the  same  end  point  as 
other  suitable  indicators  in  this  reaction  is  shown  by  Experiment  2, 
but  the  correct  end  point  for  methyl  orange  is  not  the  one  usually 
used  and  is  difficult  to  find  with  the  unaided  eye.  It  is  best  found  by 
using  the  spectroscopic  method.  {Jour.  Amer.  Chem.  Soc,  XL, 
1918.    873.)  _ 
Iodometric  Titration  of  Morphine. — This  consists  in  adding  a 
known  volume  of  decinormal  iodine  solution  to  an  acid  solution  of 
the  alkaloid.  The  resulting  per-iodide  is  filtered  out  and  the  excess 
of  iodine  determined  in  an  aliquot  portion  of  the  filtrate  (Prescott 
and  Gordin,  Jour.  Amer.  Chem.  Soc.,  XX,  727).  The  great  value 
of  this  method  lies  in  the  fact  that  by  it  morphine  may  be  determined 
without  being  first  separated  as  a  free  base.  So  many  substances 
interfere  with  its  applicability,  however,  as  to  greatly  decrease  its 
value.  Its  reliability  has  fallen  under  suspicion  through  attempts  to 
apply  it  to  other  alkaloids  which  do  not  react  with  iodine  in  the  same 
