ON  FRACTIONAL  PERCOLATION. 
337 
ON  FRACTIONAL  PERCOLATION. 
By  0.  Lewis  Diehl. 
The  recent  papers  of  Dr.  E.  R.  Squibb  on  the  Pharmacy  of 
the  Cincho7ias  and  on  Repercolation,  induced  me  to  experiment 
upon  senna  and  rhubarb,  with  a  view  to  the  preparation  of  fluid, 
extracts  from  them,  without  the  aid  of  heat.  For  several  rea- 
sons I  have  been  unable  to  conclude  mj  experiments  ;  but  during 
their  execution  some  ideas  suggested  themselves,  which  may  be 
of  interest  to  pharmacists,  and  are,  therefore,  offered  for  publi- 
cation. 
The  adoption  of  fluid  extracts  by  the  revisors  of  our  pharma- 
copoeia has  opened  a  large  and  instructive  field  to  the  pharma- 
cist. From  the  beginning  of  their  introduction  the  pharma- 
ceutic mind  has  been  agitated  with  plans  for  their  production 
in  such  state  that  they  should  accurately  represent  a  normal 
quantity  of  material.  How  far  this  has  been  accomplished  it  is 
difficult  to  say,  as  there  have  been  but  few  attempts  made  to 
determine  their  absolute  strength.  The  subject  of  heat,  in  its 
influence  on  this  class  of  preparations,  early  attracted  attention, 
and  has  been  conceded  to  influence  their  character  decidedly, 
and  in  many  cases  injuriously.  Even  when  not  directly  injurious  to 
any  active  proximate  constituent  of  the  drug,  its  application  may 
become  indirectly  injurious,  by  rendering  an  inert  principle  insolu- 
ble, thereby  causing  some  of  the  active  matter  to  be  precipitated 
with  it  mechanically  ;  or  by  the  evaporation  of  a  hydro-alcoholic 
percolate,  for  the  purpose  of  concentration,  so  to  alter  the  rela- 
tion of  the  alcohol  to  water  as  to  render  it  incapable  of  holding 
some  of  the  valuable  constituents  in  solution.  These  difficulties 
were  in  part  avoided  by  the  manipulation  suggested  by  Prof.  Gra- 
ham in  1858,  and  subsequently  by  Prof.  Procter  in  his  report  as 
a  member  of  the  Pharmacopoeia  Committee  of  the  American 
Pharmaceutical  Association.  The  improvement  of  Prof.  Gra- 
ham consisted  in  reserving  the  first  and  concentrated  portions  of 
the  percolate,  and  evaporating  the  remainder  to  such  measure- 
that,  when  mixed  with  the  reserved  portion,  the  required  quantity 
of  fluid  extract  was  formed.  On  this  plan  most  of  the  formulas- 
for  the  fluid  extracts  of  our  Pharmacopoeia  were  constructed,  and 
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