404 
PHARMACY  OF  THE  CINCHONAS. 
the  teeth.  The  residues  insoluble  in  acidulated  water  differ 
slightly  in  color  and  density  >  and  are  both  more  bitter  than  the 
other  residues.  All  the  residues  are  freely  soluble  in  weak 
alkaline  solutions,  but  those  from  acidulated  water  only  are 
bitter. 
The  percolate  from  a  pair  of  these  percolations,  after  standing 
about  four  weeks  in  the  flasks,  only  loosely  covered  from  dust, 
showed  a  bulky  looking  deposite  in  the  first  five  flasks  of  each 
percolate,  but  no  deposite  in  the  last  three  flasks.    This  deposite 
was  carefully  filtered  out  on  weighed  filters,  dried  and  weighed. 
That  from  the  alcoholic  percolate  weighed  23*8  grains  ;  and  that 
from  the  Diluted  Alcohol  percolate  22-2  grains,  or  practically 
the  same,  and  very  small  in  proportion  to  the  appearance  of  the 
deposite  when  in  the  liquid.    This  deposite  commences  to  form 
in  the  percolate  within  twenty-four  hours  after  the  percolate  is 
received,  and  as  soon  in  the  one  case  as  the  other.  That  from  the 
Alcoholic  percolate,  when  dry,  separates  from  the  filter  easily  and 
completely,  and  is  lighter  colored,  less  dense,  and  is  bitter.  That 
from  the  Diluted  Alcohol  percolate  adheres  to  the  filter,  andis  only 
partially  separated  by  scraping,  is  darker  colored,  more  dense,  and 
is  tasteless,  or  very  nearly  so.  Both  are  nearly  all  soluble  in  boil- 
ing alcohol,  and  in  great  measure  deposited  again  on  cooling. 
Both  are  nearly  all  soluble  in  a  cold  mixture  of  one-fourth  glycerin 
and  three-fourths  alcohol,  and  the  solubility  is  not  perceptibly 
increased  by  heating  ;  nor  is  there  a  perceptible  deposite  on 
cooling.    These  solutions  are  deep  blood-red,  and  pleasantly 
bitter.    They  contain  alkaloids,  but  in  too  small  a  proportion  to 
be  estimated  without  more  time  and  skill  than  the  writer  has  at 
command.  It  may  be  stated  here  as  a  matter  of  judgment, — and 
not  at  all  of  research, — that  the  proportion  of  alkaloids  in  the 
deposite  from  well-made  preparations  of  Cinchona  has  been 
commonly  over-estimated,  and  may  be  safely  disregarded  in 
practice  with  Cinchonas,  the  best  qualities  of  which  often  vary  to 
the  extent  of  a  half  to  one  per  cent,  in  the  alkaloids  they  con- 
tain.   For  example,  if  this  whole  deposite  was  alkaloids,  instead 
of  containing  only  a  small  proportion,  and  should  be  added  to 
the  previously  ascertained  alkaloid  value  of  this  bark,  it  would 
only  raise  it  from  3-4  per  cent,  to  3*7  per  cent.,  while  the  differ- 
