442  Tinctures  from  Fluid  Extracts.      { *m£7Z\m&rm' 
deleterious  use  of  heat,  and  without  subsequent  precipitation  of 
proximate  principles  with  their  necessary  removal  by  filtration,  it 
would  seem  as  though  a  tincture  made  by  diluting  such  a  fluid 
extract  should  exhibit  the  same  proximate  constituents  of  the  drug, 
in  the  same  proportions,  as  the  tincture  made  from  the  same  sample  of 
crude  drug.  But,  it  is  evident  that  this  can  be  the  case,  under  such 
conditions  only,  when  the  menstruum  used  in  the  making  of  the  fluid 
extract  is  the  same  as  thai  used  in  the  making  of  the  drug-tincture. 
A  change  in  alcoholic  strength  of  menstruum  used,  always  results 
in  a  change  of  the  proportions,  and  in  the  same  cases,  of  the  kinds 
of  proximate  principles  dissolved. 
As  an  example  of  the  influence^  changes  in  menstrua  exert,  a 
practice  of  the  last  Pharmacopoeia  may  be  cited.  In  the  making  of 
fluid  extracts,  the  1870  issue  directed  that  the  last  portions  of  the  per- 
colate should  be  evaporated  to  a  certain  volume,  and  mixed  with  the 
reserved  portion.  This  resulted  in  precipitation  of  proximate  prin- 
ciples, owing  to  the  fact  that  through  evaporation  of  the  last  portions 
of  the  percolate  the  more  volatile  alcohol  was  most  largely  removed, 
leaving  a  weakly  alcoholic  liquid  to  mix  with  a  stronger  alcoholic 
one:  hence  precipitation  occurred.  In  1880,  this  practice  was 
changed,  and  the  last  portions  of  the  percolate  are  now  evaporated 
to  extractive,  thereby  eliminating  both  alcohol  and  water,  and  this 
is  dissolved  in  the  reserved  percolate. 
As  a  rule  the  more  strongly  alcoholic  a  menstruum  used,  the 
more  rapid  the  exhaustion  and  the  less  extractive  matter  dissolved, 
while  the  more  aqueous  a  menstruum,  the  slower  the  exhaustion 
and  the  greater  the  amount  of  extractive  brought  into  solution. 
Hence,  it  is  clear,  that  a  tincture  prepared  from  a  fluid  extract 
made  with  a  certain  menstruum,  must,  of  necessity,  be  a  different 
preparation  in  the  proportion  and,  in  some  cases,  of  its  kind  of  proxi- 
mate principles,  from  a  tincture  of  a  crude  drug  made  with  a 
different  menstruum. 
It  is  a  significant  fact,  that  a  number  of  important  official  tinctures 
are  directed  to  be  made  with  menstrua  different  in  alcoholic  strength 
from  those  ordered  for  corresponding  fluid  extracts  ;  and  this  differ- 
ence makes  it  impossible,  in  such  cases,  to  obtain,  by  diluting  the 
fluid  extracts,  the  same  therapeutical  representatives  of  the  drug  as 
exhibited  in  the  drug-tinctures. 
The  following  table  of  certain  official  tinctures,  showing  the 
