The  Strength  of  Fluid  Extracts,  '  21 
the  surface  pour  on  menstruum  till  twelve  fluid  ounces  of  percolate 
have  passed ;  set  this  portion  aside,  and  continue  the  percolation  with 
the  remainder  of  the  menstruum,  and  finally  water,  till  the  buchu  is 
exhausted,  or  until  two  pints  more  of  percolate  have  been  obtained. 
Concentrate  this  by  distillation  in  a  water-bath  still  till  reduced  to 
four  fluid  ounces,  and  mix  it  with  the  reserved  percolate.  Allow  the 
mixture  to  stand  for  twenty-four  hours  and  filter  through  paper. 
The  menstruum  employed  in  this  formula  is  less  alcoholic  than  the 
Pharmacopoeia  directs,  but  it  is  sufiiciently  so  to  extract  and  retain  in 
solution  the  active  principles  of  buchu.  The  glycerin  seems  to  prevent 
the  separation  of  resinous  matter,  which  occurs  during  distillation, 
when  a  purely  alcoholic  menstruum  is  employed.  In  the  unfiltered 
fluid  extract  no  deposit  had  occurred  after  the  lapse  of  several  weeks. 
In  connection  with  this  fluid  extract  the  following  observations  may 
be  of  some  interest :  Thirty-two  troy  ounces  of  buchu  were  prepared 
in' the  manner  above  described,  and  packed  in  a  percolator  six  feet 
high  and  two  inches  wide  at  the  mouth,  gradually  tapering  to  one  and 
a  quarter  inches  at  the  bottom.  A  full  supply  of  menstruum  (alcohol 
three  parts,  water  one  part,  sp.  gr.  .895)  was  poured  on  at  the  begin- 
ning, and  percolation  commenced  on  the  second  day  after  at  the  rate 
of  about  ten  drops  a  minute.  The  percolate  was  received  in  a  small 
flask,  in  nine  separate  portions,  each  measuring  seven  and  a  half  fluid 
ounces.  The  first  portion  was  received  about  twenty-four  hours  after 
the  commencement  of  percolation,  and  the  remaining  portions  at  in- 
tervals of  about  the  same  length.  They  had  the  sp.  gr.  respectively 
of  .995,  .985,  .965,  .960,  .950,  .935,  .920,  .910,  .900.  A  mixture  of 
the  first  four  portions,  with  sufiicient  of  the  fifth  added  to  make  the 
measure  up  to  thirty-two  fluid  ounces,  had  the  sp.  gr.  .965.  A 
parallel  experiment,  conducted  in  an  ordinary  cylindrical  glass  perco- 
lator, three  and  a  half  inches  in  diameter,  and  fifteen  inches  high, 
showed  the  same  ultimate  result,  but  not  so  great  concentration  in  the 
first  portions  of  percolate — the  sp.  gr.  of  the  first  thirty-two  fluid 
ounces  being  .960  instead  of  .965  as  in  the  other  experiment.  The 
last  portion  of  percolate  had  a  very  light  color,  and  but  little  of  the 
odor  or  taste  of  buchu,  and  the  drug  may  safely  be  considered  ex- 
hausted at  that  point.  All  drugs,  however,  are  not  so  readily  ex- 
hausted as  buchu ;  and  although,  in  this  case,  thirty-two  fluid  ounces 
of  percolate  would  very  well  represent  sixteen  troy  ounces  of  drug,  it 
does  not  follow  that  it  would  be  a  safe  rule  in  all  cases ;  it  is  only  pru- 
