PHARMACY  OF  THE  CINCHONAS. 
299 
passed,  the  basin  is  to  be  rinsed  twice,  each,  time  with  water 
enough  to  fill  up  the  filter,  the  first  being  allowed  to  run  through 
before  the  second  is  poured  into  the  filter.  Next,  let  a  mixture 
of  half  a  fluidounce  of  aqua  ammonia  with  one  and  a  half  fluid- 
ounces  of  water  be  made,  and  acid  of  this  mixture  gradually, 
little  by  little,  and  with  constant  stirring,  to  the  filtered  solution 
in  the  beaker.  At  first  the  curdy  precipitate  formed  will  be 
redissolved  almost  as  fast  as  formed,  showing  an  excess  of  acid, 
and  when  the  precipitate  becomes  permanent  the  diluted  ammo- 
nia should  be  added  more  slowly  and  more  cautiously  and  at 
longer  intervals,  until  the  contents  of  the  beaker,  after  thorough 
stirring  and  with  the  vessel  containing  the  ammonia  setting  far 
off,  smell  very  faintly  of  ammonia.  The  precipitate  may  now  be 
allowed  to  settle  until  a  stratum  of  clear  liquid  is  formed  on  the 
top,  and  a  drop  or  two  of  the  diluted  ammonia  be  dropped  into 
it.  This  will  show  that  the  precipitation  is  complete  or  other- 
wise ;  and  if  complete  the  next  step  of  the  process  may  be  under- 
taken. It  is  better,  however,  to  cover  the  beaker  and  let  it 
stand  for  a  few  hours,  or  over  night,  to  secure  a  more  thorough 
precipitation  of  the  minute  portions  of  solution  that  are  caught 
and  enveloped  in  the  curdy  precipitate,  and  which  are  gradually 
squeezed  out  by  a  contraction  of  the  precipitate.  A  5-inch  round 
filter  is  to  be  carefully  weighed,  and  the  weight  marked  upon  it 
with  a  pencil,  wetted  and  adjusted  in  the  funnel,  and  the  solu- 
tion and  floating  precipitate  gradually  poured  into  it,  until  all 
the  precipitate  is  on  the  filter,  and  most  of  the  solution  drained 
through.  Rinse  the  beaker  with  water,  scratching  off  all  the 
precipitate  from  the  sides  as  clean  as  is  easily  practicable,  and 
pour  the  rinsings  upon  the  precipitate  in  the  filter.  Repeat  this 
a  second  time  and  then  allow  the  precipitate  to  drain  and  con- 
tract if  it  will.  Then  carefully  remove  the  filter  and  contents 
from  the  funnel,  and  spread  the  filter  out  by  unfolding  it  upon  a 
folded  newspaper  or  other  bibulous  paper.  When  the  filter  is 
unfolded  by  commencing  with  the  empty  folds,  the  precipitate 
will  retain  the  conical  form  of  the  funnel.  Let  this  be  carefully 
broken  up  into  small  fragments,  without  loss,  and  spread  over 
the  open  filter.  The  several  folds  of  bibulous  paper  beneath  the 
filter  soon  absorb  a  large  portion  of  the  liquid  from  the  precipi- 
