Am.  Jour.  Pharm.  \ 
October,  1899.  / 
Alkaloidal  Assays. 
463 
An  amount  of  powdered  sodium  chloride,1  equal  to  about  five  or 
six  times  the  amount  of  drug  employed,  is  then  carefully  mixed  in, 
with  use  of  the  pestle,  and  the  whole  thrown  into  a  small  percolator, 
one  provided  with  a  glass  stop-cock  and  having  a  plug  of  cotton  at 
the  bottom.2 
The  vessel  is  then  cleaned  out  several  times  with  small  quantities 
of  sodium  chloride,  and  the  cleanings  added  to  the  percolator.  The 
mixture  in  the  percolator  is  then  covered  with  a  little  of  the  cotton, 
which  is  pressed  down  with  a  piece  of  glass,  and  a  suitable  men- 
struum, usually  chloroform,  is  poured  slowly  into  the  percolator, 
till  the  menstruum  reaches  the  stop-cock.  The  latter  is  then  closed, 
the  percolator  covered  and  set  aside  for  five  or  six  hours.  After 
that  time  the  stop-cock  is  opened,  and  the  drug  exhausted  with  the 
menstruum,  percolating  until  ten  drops  of  the  percolate  being  evapo- 
rated on  a  watch-glass,  and  the  residue  taken  up  with  a  few  drops 
of  acidulated  water,  the  solution  shows  no  turbidity  whatever  on  adding 
a  few  drops  of  the  solution  of  iodine.  When  finished,  the  percolate, 
which  is  received  in  a  flat  evaporating  dish,  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  water3  are  added,  and  then 
a  few  cubic  centimeters  of  ether,  or  petroleum  ether,  so  as  to  have 
an  ethereal  liquid  cover  the  aqueous  solution,4  when  the  whole  is 
stirred  with  a  glass  rod  until  all  the  ethereal  liquid  is  driven  off. 
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  worked  up  for  any 
method  of  estimation.5 
1  In  the  case  of  Hydrastis  the  sodium  chloride  is  replaced  by  barium  nitrate. 
2  A  suitable  percolator  is  easily  made  out  of  an  ordinary  piece  of  glass  tubing 
fitted  with  a  perforated  cork,  through  which  passes  a  tube  having  a  glass  stop- 
cock. 
3  If  an  alkalimetric  assay  is  intended,  the  acidulated  water  in  the  operation 
should  be  closely  standardized  and  taken  in  definite  quantities. 
4  If  the  menstruum  is  all  evaporated  off  it  is  sometimes  difficult  to  dissolve 
out  the  alkaloids  with  the  acidulated  water.  If  chloroform  be  used,  coming 
below  the  aqueous  layer,  it  evaporates  too  slowly. 
5  The  method  of  extraction  described  above  presents  particular  advantage 
in  those  cases  where  several  alkaloids  soluble  in  different  menstrua  are  present 
in  the  drug,  as  by  using  these  menstrua  successively  a  separation  of  the  alka- 
loids can  be  easily  effected.  This  principle  we  have  applied  to  the  assay  of 
opium,  and  to  that  of  Hydrastis  canadensis. 
