2 1  o  Fluid  Extracts  by  Reper eolation.      { Jf"* 
percolate  to  obtain  the  established  relation  between  the  drug  and  the 
fluid  extract  presents  difficulties  which  are  probably  insurmountable  by 
that  process.    It  is  not  simply  by  the  heat  and  oxidation  of  the  evapo- 
ration process  that  all  the  harm  is  done  to  that  portion  of  the  prepara- 
tion, but  the  active  principles  are  so  dissociated  and  split  up  by  the 
concentration  that  they  are  no  longer  in  their  natural  condition,  but 
form  new  relations  and  combinations  which  change  their  solubilities, 
and  bring  a  new  set  of  reactions  into  play,  making  the  preparation 
something  else  than  what  it  professes  to  be.    The  evidence  of  this  is 
found  in  the  fact  that  a  resinous  or  oleaginous  drug  can  be  thoroughly 
exhausted  by  a  menstruum  which  will  permanently  hold  all  its  constit- 
uents in  solution.    But  if  such  menstruum  be  evaporated  off,  the  same 
menstruum  will  not  dissolve  and  hold  the  extract  again.     Nor  will  any 
other  menstruum  ever  again  reconstruct  the  extract  or  restore  it  to  its 
original  condition.    For  example  a  diluted  alcohol  will  exhaust  Buchu 
and  will  hold  the  oil,  while  in  its  natural  relations  with  other  constitu- 
ents of  the  leaf,  in  the  same  kind  of  combination  or  emulsion  that 
exists  in  the  leaf  before  extraction,  and  in  such  a  solution,  though  very 
dense,  the  oil  does  not  change  in  odor  much, — if  at  all  more  rapidly 
than  the  leaf  does.    But  if  such  a  solution  be  evaporated  until  the  oil 
is  precipitated  and  shows  itself  as  a  fully  formed  oil,  the  same  strength 
of  alcohol  will  not  redissolve  it.     Nor  will  any  strength  of  alcohol 
redissolve  the  whole  of  the  extract,  or  recombine  its  once  separated 
elements  into  their  natural  condition.     And  moreover,  the  oil  when 
separated,  changes  its  physical  properties  more  rapidly  than  when  in 
its  natural  condition  in  the  leaf,  or  than  when  separated  with  its  natural 
associations  unbroken.   These  circumstances  constitute  the  chief  objec- 
tion to  the  original  process,  and  to  many  of  the  original  menstrua  of 
Prof.  Procter,  and  led  the  present  writer  to  try  to  make  improvements 
both  in  the  process  and  the  menstrua. 
This  effort  at  improvement  by  the  writer  was  begun  in  a  paper  pub- 
lished in  the  Proceedings  of  The  Amer.  Pharm.  Asso.  for  1865,  p. 
201.  To  diminish  the  proportion  of  alcohol  in  the  menstrua,  and  to 
economize  its  use,  were  the  principal  objects  of  this  paper,  and  it  is 
cited  here  for  reference  in  regard  to  the  importance  of  the  points  there 
insisted  upon,  because  these  points  have  not  attracted  the  attention  they 
deserve. 
The  effort  at  improvement  was  continued  in  1866  by  a  paper  pub- 
