410 
Quinine  Testing. 
/Am.  Jour.  Pharm.. 
t      August,  1887. 
modifications  I  have  suggested.  It  requires,  however,  the  use  of 
very  pure  ether,  as  is,  indeed,  the  case  with  every  form  of  cinchoni- 
dine  determination  that  is  carried  out  with  ether.  The  modification 
of  this  test  introduced  by  Schafer  is  less  to  be  relied  upon,  probably 
because  the  evaporation  of  the  ether  solution  is  attended  with  such  a 
concentration  of  the  quinine  as  to  have  the  effect  of  hindering  the 
crystallization  of  the  alkaloid  or  its  compound.  It  may  be  for  this 
reason  that  Schafer  was  unable  to  obtain  crystals  of  "  cinchonidine  " 
in  operating  upon  quinine  sulphate  known  to  contain  2  per  cent,  of 
cinchonidine  sulphate.  I  have  no  hesitation  in  affirming  that  the 
crystals  obtained  by  the  bisulphate  test,  as  modified  by  Schafer  and 
described  by  him  as  "  pure  cinchonidine,"  are  a  compound  of  quinine 
with  two  molecules  of  cinchonidine.  As  I  have  shown  on  another 
occasion,  this  bisulphate  method  always  gives  a  cinchonidine  result 
that  is  too  high  in  the  case  of  a  sample  containing  only  a  small 
amount,  and  with  one  containing  a  larger  amount  the  result  obtained 
is  too  low.  On  the  whole,  however,  the  results  obtained  by  this  test 
are  very  satisfactory,  and  they  are  obtained  with  one  operation,  while 
the  recrystallization  test,  recommended  by  Dr.  Paul,  appears  to  re- 
quire several  successive  operations. 
It  is  well  known  that  Paul  was  the  first  to  direct  attention  to  the 
occasionally  considerable  amount  of  cinchonidine  sulphate  in  the  qui- 
nine sulphate  of  commerce.  His  method  of  ascertaining  the  amount 
of  this  impurity  consists  in  dissolving  5  grams  of  the  salt  in  question 
in  150  c.c.  of  boiling  water  and,  after  cooling  the  solution,  treating  the 
mother-liquor  thus  obtained  with  ammonia  and  ether.  The  recrystal- 
lized  sulphate  is  to  be  again  treated  with  100  c.c.  of  boiling  waterr 
and  the  mother  liquor,  obtained  after  cooling,  subjected  to  treatment 
with  ammonia  and  ether,  this  operation  being  repeated  until  no  more 
crystals  are  deposited  from  the  ether  solution  thus  obtained.  These 
crystals,  however,  are  not  pure  cinchonidine,  but  the  compound  already 
mentioned.  Consequently  the  amount  of  cinchonidine  indicated  by 
weighing  them  is  too  high  by  the  amount  of  quinine  they  contain.  If 
the  mother-liquors  were  treated  with  ether  direct  this  surplus  would 
be  to  some  extent  reduced  by  the  circumstance  that  it  would  not  then 
be  possible  to  obtain  the  whole  of  the  cinchonidine  in  a  state  for 
weighing.  But  if  the  mother-liquors  are  concentrated  by  evaporation 
so  as  to  allow  of  less  ether  being  used,  satisfactory  results  are  readily 
obtained.    The  mode  of  procedure  I  adopt  in  applying  this  test  is  to 
