i6o  Contributions  from  H.  M.  Gordin.  {^l^mi™' 
of  an  equal  amount  of  talcum.  In  this  way  the  final  estimation  of 
the  isolated  alkaloid  presents  no  difficulty  whatever. 
The  only  other  condition  upon  which  the  exactness  of  a  drug  as- 
say depends  is,  then,  the  complete  extraction  of  the  alkaloids.  In 
the  case  of  fluids,  the  complete  extraction  of  the  alkaloids  presents 
no  difficulty.  By  the  aid  of  immiscible  solvents  we  can  either  di- 
rectly, or  after  a  few  very  simple  operations,  separate  the  alkaloids 
from  the  other  plant  constituents  with  such  completeness  that  no 
known  reagent  will  show  the  presence  of  alkaloid  in  the  exhausted 
liquid.1 
But  the  case  is  entirely  different  with  solid,  not  wholly  soluble 
substances,  particularly  crude  drugs.  The  complete  exhaustion  of 
crude  drugs  is  sometimes  connected  with  such  difficulties  that  very 
often  fluid  extracts  contain  much  less  alkaloid  than  is  known  to  be 
contained  in  the  drug  which  the  extracts  are  supposed  to  represent. 
It  is  well  known,  for  example,  that  fluid  extract  nux  vomica,  as 
sent  out  by  most  manufacturers,  contains  only  about  i}4  per  cent, 
of  total  alkaloids,  whereas  the  drug  itself  generally  contains  from 
3  to  ^/i  Per  cent.  In  the  Pharmacopceial  directions  for  making 
fluid  extracts  we  are  told  to  continue  the  percolation  till  the  drug 
is  exhausted.  But  how  are  we  to  know  when  the  drug  is  ex- 
hausted ?  That  the  absence  of  appreciable  quantities  of  alkaloid 
in  a  few  drops  of  the  percolate  is  not  sufficient  proof  of  complete 
exhaustion  was  shown  in  a  previous  paper,2  in  the  case  of  colchi- 
cum.  The  only  way  to  prove  the  completeness  of  exhaustion  is  to 
test  the  dregs  qualitatively  for  alkaloids.  This  can  be  easily  ac- 
complished by  removing  the  dregs  from  the  percolator,  drying 
-  them  and  then  digesting  a  few  hours  with  Prollius*  fluid.  After 
filtering  and  shaking  out  with  acid  water,  the  presence  or  absence 
of  alkaloidal  matter  can  be  ascertained  by  means  of  the  general 
alkaloidal  reagents. 
If  this  method  of  testing  the  completeness  of  exhaustion  be 
applied  to  many  of  the  methods  which  have  been  proposed  for  the 
extraction  of  alkaloids  for  assay  purposes,  it  will  be  found  that  most 
of  these  methods  are  very  far  from  securing  complete  exhaustion. 
1  The  great  exactness  of  separation  by  immiscible  solvents  can  be  deduced 
from  a  formula  given  in  Ostwald's  "  Analytische  Chemie." 
2  Gordin  and  Prescott.  Paper  read  at  the  meeting  of  the  A.Ph.A.,  at  Rich- 
mond, Va.,  1900. 
