*S43£r!iSr }  Fluidgly  cerates.  527 
In  the  more  extended  work,  a  number  of  practical  problems  pre- 
sented themselves  and  had  to  be  overcome.  The  process  of  percola- 
tion was  adopted  wherever  practical  in  the  extraction  of  the  drugs, 
but  it  was  found  that  percolation  with  glycerin-water  menstruum 
was  somewhat  more  difficult  than  ordinary  percolation  with  hydro- 
alcoholic  liquids.  The  tendency  to  pack,  "  clog  "  and  "  block  "  the 
percolation  is  pronounced  and  each  drug  has  to  be  studied  to  de- 
termine the  best  method  of  procedure  to  overcome  this  trouble. 
As  a  rule  the  drug  should  be  ground  very  much  coarser  than  ordered 
by  the  Pharmacopoeia  for  the  making  of  tinctures  and  fluidextracts. 
The  penetrating"  property  of  glycerin  is  so  marked  that  usually  a 
number  twenty  powder  is  sufficiently  fine  to  yield  good  results.  With 
fine  powders  an  inert  substance  must  be  admixed  and  here  again  a 
selection  is  required ;  for  guarana  coarse  sharp  sand  was  satisfactory 
and  for  gambir  pumice  stone,  not  too  fine,  was  needed.  Thorough 
and  even  moistening  of  the  drug  is  essential  and  the  packing  in  the 
percolator  must  be  even,  but  it  must  not  be  firmly  or  tightly  packed ; 
the  rapidity  of  percolation  being  best  controlled  by  means  of  a 
compressor  on  the  exit  tube.  A  few  drugs  are  not  amenable  to 
percolation  with  glycerin-water  mixture,  senna  leaves  being  a  notable 
example,  and  for  such  either  of  the  following  methods  must  be 
adopted,  maceration  with  the  menstruum  and  expression,  or  an 
aqueous  infusion  prepared  and  concentrated  to  which  the  glycerin 
can  be  added. 
Another  problem  that  presented  itself  was  the  tendency  of  the 
drug  in  the  percolator  to  undergo  fermentation  and  even  putrefac- 
tion before  the  final  extraction  with  water  was  completed.  In  warm 
weather  this  tendency  was  very  evident.  It  was  found  that  by  using 
chloroform  water  instead  of  distilled  water  in  forcing  out  the  balance 
of  the  first  menstruum  and  in  finishing  the  extraction,  this  was 
effectually  overcome.  The  chloroform  is  entirely  dissipated  in  the 
evaporation  on  the  water  bath. 
In  my  original  paper  I  recommended  that  the  first  60  parts  of  the 
percolate  be  set  aside  as  a  reserve.  Subsequent  work  demonstrated 
that  this  was  not  always  practical  as  the  remaining  portion  of  the 
percolate  frequently  contained  so  much  matter  in  solution  that  it  was 
not  advisable  to  concentrate  it  to  40  parts,  and  consequently  I  have 
adopted  50  parts  for  reserve.  The  remainder  of  the  percolate  is 
concentrated  to  60  parts,  the  reserve  added,  and  the  product  concen- 
trated to  100  c.c.  for  each  100  Gm.  of  drug  used. 
