214  Fluid  Extracts  by  Reper eolation.  {AmkJa0y,r*33p78arm' 
affords  good  exhaustion,  and  a  fluid  extract  which  weighs  7685  grains 
to  the  pint.  This  is  almost  exactly  minim  for  grain  and  weight  for  weight. 
But  as  the  drug  never  is  quite  exhausted  even  under  the  very  best  man- 
agement the  measure  never  should  have  been  made  minim  for  grain  if 
the  drug  was  to  be  fairly  and  fully  represented  by  the  fluid  extract.  As 
a  rule  of  actual  practice,  the  drug  will  not  often  be  exhausted  within  5 
or  10  per  cent,  and  by  the  officinal  management,  will  fall  greatly  below 
this.  A  more  accurate  proportion  would  have  been  90  to  95  minims  to- 
each  100  grains  of  drug  or  about  8000  grains  of  drug  to  make  a  pint 
of  fluid  extract  each  minim  of  which  should  represent  a  grain  of  the 
drug.  Even  by  repercolation  some  such  excess  is  needed  to  make  the 
therapeutic  relation  what  it  professes  to  be.  Beside  this  objection  of 
being  too  close  in  theoretical  relation  to  be  true  in  practical  value,  this 
menstruum  has  long  been  believed  to  be  unnecessarily  strong  in  alcohol,, 
and  containing  too  much  glycerin.  The  glycerin  in  many  cases  has 
a  secondary  use  in  menstrua  which  is  hardly  less  important  than  its 
primary  use  as  a  solvent.  It  has  the  property  of  wetting  substances, 
and  permeating  them  to  the  exclusion  of  air,  to  a  much  greater  degree 
than  water  or  alcohol,  and,  when  mixed  with  water  or  alcohol  imparts 
this  property  to  the  mixture.  When  used  at  all,  therefore,  it  must  be 
used  with  both  these  functions  in  view,  and  one  step  beyond  this  is 
objectionable.  After  a  preliminary  set  of  percolations  with  this  old 
menstruum  to  observe  how  it  would  work  on  the  small  scale  of  4  troy 
ounces  of  powder  to  each  percolation,  a  new  menstruum  was  tried  con- 
sisting of  2  parts  stronger  alcohol,  2  parts  water  and  1  part  glycerin,, 
and  a  preliminary  set  of  percolations  upon  the  same  scale  of  4  troy 
ounces  gave  good  results,  but  proved  that  the  scale  was  so  small  as  to- 
need  especial  skill  and  care  in  order  to  attain  the  desired  accuracy. 
Another  tentative  trial  was  then  made  with  this  new  menstruum  on  a 
scale  of  8  avoirdupois  ounces  at  each  percolation,  and  this  proved  to  be 
a  much  less  troublesome  scale.  And(,  for  Cinchona  it  is  about  as  small 
a  scale  as  can  be  worked  to  advantage.  An  avoirdupois  pound  would 
be  better  and  easier  still.  The  details  of  these  trials  need  not  be  given,, 
and  it  is  sufficient  to  say  that  they  indicated,  and  gave  a  part  of  the 
necessary  experience  needed  for  another  careful  trial,  in  which  two  very 
important  points  were  still  to  be  settled,  namely  the  proportion  of  men- 
struum and  weak  percolate  that  was  best  to  moisten  the  powder,  and  the 
length  of  time  that  was  best  to  macerate  each  portion,  the  trials  having 
