308 
Tincture  of  Rhubarb. 
(Am.  Jour.  Phakm. 
'(      July  1,1873.  ' 
the  case  when  the  percolate  contains  tannin,  starch  and  other  proxi- 
mate principles,  which,  when  thus  associated  together,  are  liable,  even 
at  ordinary  temperatures,  to  undergo  changes  unfavorable  to  the  sta- 
bility of  the  finished  product.  Hence  the  importance  of  attention  to 
this  apparently  trivial  matter. 
The  frequent  agitation  of  the  percolate  during  the  process  of  per- 
colation intermixes  the  denser  portions  with  the  successive  and  less, 
densely  saturated  portions  as  they  pass.  It  not  unfrequently  hap- 
pens that,  when  percolation  is  slow,  several  days  are  consumed  before 
the  completion  of  the  process,  so  that  the  denser  portions,  if  allowed 
to  remain  undisturbed,  are  most  sure  to  deposit  more  or  less  matter,, 
which  although  it  is  frequently  very  readily  redissolved,  is  not  so 
likely  to  remain  afterwards  in  permanent  solution.  At  least  this  has 
been  my  experience  while  carefully  and  closely  observing  very  fre- 
quent manipulations  of  this  kind.  # 
There  are  obscure  chemical  and  molecular  changes  which  may  occur 
under  such  circumstances,  as  the  result  of  oxidation  and  other  influ- 
ences, in  consequence  of  the  nascent  condition  of  the  vegetable  princi- 
ples, and  these  changes  but  few  could  divine  or  explain.  It  therefore 
behooves  usall'to  adopt  every  expedient  in  our  manipulations  that 
may  suggest  itself,  to  guard  against  the  possibility  of  such  results. 
After  the  percolation  in  any  instance  has  sufficiently  advanced  that, 
the  solid  matter  extracted  is  mixed  with  sufficient  of  the  menstruum 
to  hold  it  in  solution,  then  the  agitation  of  the  percolate  be  no  longer 
continued,  and  the  superstratum  which  accumulates  may  serve  a  good 
purpose,  in  some  instances,  in  protecting  the  stronger  portions  be- 
neath from  the  action  of  the  air  during  the  exposure  necessary  to 
complete  the  process. 
The  deposit  occurring  in  the  officinal  tincture  of  rhubarb  very  often 
not  only  covers  the  bottom  of  the  bottle  with  a  deposit  of  from  a 
quarter  to  a  half  inch  in  depth,  but  the  sides  of  the  bottle  most  ex- 
posed to  the  direct  light  also  receive  their  share  of  coating. 
The  above  formula  does  not  entirely  remedy  the  defect,  but  it  so 
nearly  accomplishes  the  object  as  to  render  the  tincture  as  prepared 
by  it  a  much  more  satisfactory  preparation.  The  deposit  accumulat- 
ing in  a  quart  of  the  tincture  made  by  this  formula  on  the  5th  of  last 
February  is  at  this  time  so  slight  when  compared  with  that  usually 
occurring  in  the  officinal  tincture,  that  it  really  appears,  practically, 
of  but  little  consequence.  The  tincture,  made  as  above  directed,  does 
