126   PROPOSED  ECONOMY  OF  ALCOHOL  IN  PERCOLATION,  ETC. 
and  two  hundred  and  ten  thousandths  twentieths  (■6^01J>=31,051 
per  cent.)  of  the  whole  medicinal  part  of  the  extract.  Hence, 
the  second  column,  which  gives  the  percentage  of  the  total  ex- 
tract, inert  and  medicinal  together,  also  indicates  the  percentage 
of  medicinal  extract  alone,  since  a  percentage  is  the  same, 
whether  calculated  upon  the  1756  grains  of  total  extract,  inert 
and  medicinal  together,  or  upon  the  351  grains  of  medicinal 
extract  alone,  if  the  ratios  he  preserved. 
It  will  be  seen  by  this  table,  that  the  proportion  of  menstru- 
um adopted  by  the  Pharmacopoeia  for  moistening  the  powder 
before  packing  is  not  the  best.  Secondly,  That  there  is  a  re- 
markable difference  in  different  lots  of  good  bark,  both  in  the 
progress  of  exhaustion  and,  as  noticed  before,  in  the  character 
of  the  percolate  in  regard  to  the  tendency  to  deposit  less  soluble 
matters,  whilst  the  total  amount  of  extract  yielded  and  the  pro- 
portion of  alkaloids  may  not  vary  widely.  Length  of  time 
seems  to  have  much  to  do  with  this  tendency  to  deposit,  and 
possibly  may  account  for  the  whole  difference  in  this  way.  The 
new  bark  was  in  very  fine  powder,  and  was  packed  about  as 
tightly  in  the  percolator  as  the  old.  This  caused  it  to  percolate 
much  more  slowly  ;  indeed,  it  percolated  extremely  slow, — was 
more  than  48  hours  in  starting,  and  then  gave  about  eight  fluid- 
ounces  in  24  hours.  Under  these  circumstances,  we  may  suppose 
that  the  menstruum,  which  became  saturated  with  the  less  soluble 
matters,  had  time  to  deposit  them  again  before  escaping  as  per- 
colate. The  percolate  might  thus  remain  clear,  as  this  did,  and 
this  process  of  solution,  deposition,  and  resolution  in  the  mass, 
would  naturally  postpone  the  final  exhaustion  of  the  powder, 
and  distribute  the  extract  obtained  through  a  larger  portion  of 
the  percolate,  without  materially  affecting  the  total  amount  of 
extract,  as  really  happened  in  the  case  of  this  bark,  let  the  cause 
be  what  it  may.  These  conditions  and  circumstances  would  not 
obtain  in  any  known  case,  except  that  of  cinchona  bark,  and 
therefore  this  is  a  good  example  of  the  most  precarious  and  un- 
favorable application  of  economical  percolation.  Thirdly,  That 
under  ordinary  favorable  circumstances,  the  first  12  fluidounces, 
or  the  reserved  percolate  in  calisaya  bark,  contains  over  75  per 
cent,  of  its  total  value ;  the  first  pint  over  86  per  cent.,  and  the 
