522 
ON  FLUID  EXTRACTS. 
that  cold  percolation,  with  the  proper  menstruum,  is  the  true 
way  to  exhaust  from  a  plant  its  soluble  medicinal  principles. 
The  details  of  this  process  have  been  so  often  described  that  any 
remarks  from  me  are  hardly  required.  Quite  recently  an  able 
paper  upon  this  subject,  with  illustrations  of  apparatus,  has  been 
published  by  Dr.  Squibb,  in  the  Journal  of  Pharmacy.  It  may 
be  well,  therefore,  to  proceed  at  once  to  the  choice  of  a  men- 
struum. 
Our  fathers  in  Pharmacy,  when  they  selected  the  officinal 
diluted  alcohol  as  a  menstruum  for  making  tinctures,  chose  one 
that  is  an  almost  universal  solvent  for  the  principles  of  vegetable 
remedies.  The  union  of  alcohol  and  water,  in  equal  proportions, 
forms  the  menstruum  proper  for  by  far  the  larger  portion  of 
those  articles  from  which  Fluid  Extracts  are  made.  Even  jalap 
and  mandrake,  the  active  part  of  which  are  resins,  will  yield  to 
it  their  virtues.  Although  these  resins,  when  obtained  and 
purified,  will  not  dissolve  in  this  menstruum,  they,  in  their 
natural  state,  combined  with  extractive,  are  dissolved  and  ex- 
tracted from  the  root.  The  use  of  diluted  alcohol  for  plants  of 
a  resinous  nature  has  an  advantage  over  the  plan  of  percolating 
first  with  alcohol,  then  with  water,  and  subsequently  uniting  the 
products.  By  the  first,  the  original  union  is  not  broken,  the 
resin  and  extractive  are  exhausted  together,  and  in  the  per- 
fected Extract  this  union  is  easily  preserved :  by  the  latter 
method,  much  precipitation  occurs  when  the  two  products  are 
mixed. 
For  those  articles  whose  properties  are  of  a  volatile  nature, 
as  buchu,  valerian,  and  cubebs,  this  menstruum  will  not  answer, 
for  this  reason, — unless  the  menstruum  be  more  volatile  than 
the  contained  principles,  the  latter  will  be  lost  during  evapora- 
tion ;  therefore,  for  this  class  of  substances,  alcohol  or  ether  is 
required,  either  of  which  can  be  distilled  off,  leaving  behind  the 
desired  principles. 
As  a  general  rule,  therefore,  we  may  say,  that  for  articles  not 
possessing  volatile  principles,  diluted  alcohol  is  the  proper  men- 
struum. This  rule  has  exceptions,  as  in  the  case  of  senna,  which 
forms  a  finer  Extract  with  cold  water,  and  Cannabis  Indica, 
which  requires  strong  alcohol.  The  other  class,  those  possess- 
ing volatile  principles,  should  be  percolated  with  deodorized  al- 
cohol until  exhausted,  then  with  water,  and  the  two  products 
