232  Extr actum  Pruni  Virginiance  Fluidum.  {AmMayy'i887arm* 
complished  in  the  direction  of  ridding  the  product  of  this  constituent 
of  the  drug,  unless  indeed  we  should  have  resort  to  an  expedient  of 
perhaps  questionable  propriety  and  add  to  the  macerate  a  small  quan- 
tity of  some  acid,  thus  rendering  the  tannin  less  soluble ;  experiments 
in  this  direction  have  however  not  been  made. 
The  presence  of  a  precipitate  is  due  to  the  fact  that  the  menstruum 
of  dilute  alcohol  is  not  allowed  to  thoroughly  mix  with  the  macerate 
before  percolation  begins,  thus  the  first  part  of  the  percolate  differs 
from  the  last  part  •  this  must  naturally  cause  a  precipitate. 
The  following  formula  has  yielded  excellent  results  and  develops 
all  the  prussic  acid ;  there  is  no  precipitate  nor  does  any  form  on 
standing  as  will  be  seen  from  the  specimen  which  is  seven  months  old 
and  has  never  been  filtered  ;  and  I  had  a  specimen,  which  has  unfor- 
tunately been  mislaid,  which  was  over  a  year  old  and  is  identical  in 
appearance  and  odor  with  this  : 
Take  of  Ground  Wild  Cherry  Bark..  §  xvi. 
Water  and  Alcohol,  each  f^x. 
Glycerin  .  giv. 
Moisten  the  bark  with  §x  of  water  and  put  loosely  in  the  percola- 
tor, close  tightly  and  allow  it  to  macerate  sixty  hours ;  then  pack  very 
firmly,  mix  the  ten  fluidounces  of  alcohol  and  four  of  glycerin  and 
pour  it  upon  the  bark,  now  cork  up  the  percolator  tightly  and  macer- 
ate twenty-four  hours  longer ;  at  the  expiration  of  this  time  remove  the 
cork  and  about  twelve  fluidounces  of  percolate  will  come  through ; 
water  should  now  be  poured  on  to  force  the  other  four  fluidounces 
out  when  the  percolation  should  be  stopped  and  the  product  will  be 
finished.  After  an  extended  experience  the  conclusion  was  reached  that 
to  continue  the  percolation  beyond  this  point  is  worse  than  useless  as 
it  necessitates  subsequent  evaporation ;  nor  does  it  add  any  medicinal 
strength  to  the  preparation.  It  does  add  quite  a  considerable  quantity  of 
tannin  and  gallic  acid,  which  latter  results  from  the  conversion  of  the 
tannin  by  heat. 
