1 6  Emetine  Octoiodide  and  Alkaloids.     { A ^ii^y^m' 
with  small  quantities  of  sodium  chloride,  and  the  cleanings  added 
to  the  percolator.  The  mixture  in  the  percolator  is  then  covered 
with  a  piece  of  cotton,  which  is  pressed  down  with  a  piece  of  glass, 
and  a  suitable  menstruum,  usually  chloroform,  is  poured  slowly  into 
the  percolator  till  the  menstruum  reaches  the  stopcock.  The  latter 
is  then  closed,  the  percolator  covered,  and  set  aside  for  five  or  six 
hours.  After  that  time  the  stopcock  is  opened,  and  the  drug 
exhausted  with  the  menstruum,  percolating  until  ten  drops  of  the 
percolate  evaporated  on  a  watch  glass,  and  the  residue  taken 
up  with  a  few  drops  of  acidulated  water,  shows  no  turbidity 
whatever  on  adding  a  few  drops  of  Wagner's  reagent.  The 
percolate  is  received  in  a  flat  evaporating  dish,  and  when  finished  is 
placed  in  a  good  draught  at  a  temperature  of  about  300  C.  When 
the  liquid  is  reduced  to  a  very  small  volume,  10  c.c.  of  acidulated 
water7  is  added,  and  then  a  few  cubic  centimeters  of  ether  or 
petroleum  ether,  so  as  to  have  an  ethereal  liquid  cover  the  aqueous 
solution,8  when  the  whole  is  stirred  with  a  glass  rod  until  all  the 
ethereal  liquid  is  driven  ofT.  The  liquid  is  then  filtered  and  the 
evaporating  dish  and  filter  washed  several  times  with  acidulated 
water.  In  this  way  is  obtained  a  colorless  solution  of  the  alkaloid, 
which  can  be  taken  for  any  method  of  assay. 
In  the  periodide  method  of  assay  the  final  alkaloidal  solution  ob- 
tained, whether  by  our  method,  by  Dr.  Lyons'  method,  or  by  any 
other  method,  this  final  solution  representing  a  definite  quantity  of 
the  drug  to  be  assayed,  is  poured  slowly  and  with  constant  stirring 
into  a  flask  holding  100  c.c,  into  which  has  been  previously  drawn 
20  or  30  c.c,  of  a  standardized  solution  of  iodine  and  1  or  2  c.c.  of 
dilute  hydrochloric  acid9  (U.S.P.).  The  flask  is  then  filled  up  to 
100  c.c,  stoppered  and  well  shaken  till  the  periodide  has  separated 
out.  The  supernatant  liquid  is  to  be  perfectly  transparent  but  of  a 
red  iodine  color.  Fifty  c.c.  are  then  filtered  off,  and  in  this  portion 
the  excess  of  iodine  determined  by  means  of  standard  sodium  thio- 
7  If  an  alkalimetric  assay  is  intended  the  acidulated  water  in  the  operation 
should  be  standardized  and  taken  in  definite  quantities. 
8  If  the  menstruum  is  all  evaporated  off  it  is  sometimes  difficult  to  dissolve 
out  the  alkaloids  with  acidulated  water.  If  chloroform  be  used,  coming  below 
the  aqueous  layer,  it  evaporates  too  slowly. 
9  Except  in  a  case  of  morphine  an  excess  of  acid  is  not  hurtful  and  even 
promotes  the  separation  of  the  periodide.  Hydrochloric  is  preferable  to 
sulphuric  acid. 
