300 
PHARMACY  OB  THE  CINCHONAS. 
tate,  and  this  may  then  be  broken  up  still  finer.  It  is  then 
dried  perfectly,  first  by  exposure  for  12  hours  at  ordinary  tem- 
peratures, and  then  by  placing  the  whole,  bibulous  paper  and  all, 
in  some  warm  place,  with  free  circulation  of  air,  but  protected 
from  dust  and  accidental  loss,  for  12  hours  more.  If  the  tem- 
perature be  too  high  the  alkaloids  will  melt  and  contract,  and 
adhere  to  the  paper,  but  this  does  not  affect  the  result  if  they 
have  been  so  spread  over  the  filter  as  to  prevent  the  formation 
of  masses  which  might  retain  moisture  within  them.  At  the  end 
of  the  24  hours'  drying  take  up  two  sides  of  the  filter  so  that  the 
precipitate  may  fall  toward  the  centre,  if  it  moves  on  the  paper, 
and  place  the  filter  and  contents  on  the  scale.  Weigh  the  whole 
carefully,  and  subtract  the  weight  of  the  filter.  The  remainder 
is  of  course  the  weight  of  the  impure  mixed  alkaloids  from  the 
1000  grains  of  powdered  Cinchona.  If  the  Cinchona  be  of  good 
quality  this  quantity  should  yield  from  28  to  30  grains.  If  of 
very  good  quality  from  31  to  34  or  35  grains,  and  this  weight  is 
converted  into  per  centage  by  simply  placing  a  decimal  point 
immediately  to  the  right  of  the  first  or  left  hand  figure.  Thus, 
if  1000  grains  of  Cinchona  yield  31  grains  of  impure  mixed  alka- 
loids, this  is  equal  to  34  per  cent.  If  it  yield  31*6  grains  this 
is  equal  to  3-16  per  cent,  in  the  Cinchona,  and  the  results  may 
then  be  applied  to  any  larger  quantity  by  simple  arithmetic. 
These  mixed  alkaloids  are  commonly  of  a  dark  cream  color  when 
dry,  unless  contraction  or  fusion  has  occurred,  when  they  are 
still  darker,  and  they  are  quite  impure,  so  that  the  valuation 
obtained  by  weighing  them  is  too  high  by  say  about  10  per  cent, 
of  their  weight.  For  example,  a  Cinchona  which  yields  34 
grains,  or  3*4  per  cent,  of  its  weight  of  these  impure  mixed  alka- 
loids, does  not  yield  more  than  3-4  less  0-34  equal  3*06  per  cent, 
of  pure  mixed  alkaloids.  This,  of  course,  is  only  a  rough  prac- 
tical estimation,  but  still  very  useful,  until  we  all  learn  to  be 
more  skilful  and  accurate.  In  order  to  show  the  want  of  any- 
thing like  absolute  accuracy  in  this  process  it  is  only  necessary 
to  add  a  few  drops  of  the  diluted  ammonia  to  the  clear  liquor 
filtered  off  from  the  precipitate.  In  nine  cases  out  of  ten  this 
will  cause  a  very  decided  milkiness  and  precipitation,  indicating 
the  presence  of  alkaloids.    This  is  in  consequence  of  the  small 
