Am.  Jour.  Pharm.l 
August,  1887.  J 
Quinine  Testing. 
409 
into  solution,  while  the  quinine  salt  remains  almost  entirely  undis- 
solved. If  it  were  possible  to  leave  the  quinine  salt  completely 
undissolved  there  would  be  no  reason  to  fear  any  loss  of  cinchonidine 
sulphate,  but  some  of  the  quinine  sulphate  is  dissolved  at  60°  C,  and 
thus  opportunity  is  afforded  for  a  small  portion  of  the  dissolved 
cinchonidine  salt  to '  form  a  certain  quantity  of  a  double  compound, 
which  is  afterwards  deposited  in  amount  corresponding  to  its  solu- 
bility. Thus  it  happens  that  the  whole  of  the  cinchonidine  is  not 
obtained  in  solution  in  such  an  experiment.  But  in  any  case  such  a 
mode  of  extraction  is  more  complete  than  when  the  sulphate  is  boiled 
with  water,  or  dissolved  in  boiling  water,  since  in  the  latter  case  there 
will  be  not  only  a  decomposition  of  quinine  sulphate  attended  with 
elimination  of  quinine  (which  can  be  extracted  by  benzol),  but  since 
a  greater  part,  and  perhaps  the  whole,  of  the  quinine  sulphate  will 
then  pass  into  solution,  a  larger  portion  of  the  cinchonidine  sulphate 
will  again  become  latent  from  formation  of  the  double  salt  when 
crystallization  takes  place.  For  this  reason  I  cannot  approve  of  the 
modification  in  my  original  test  which  Schafer  suggested,  nor  can  I 
confirm  the  condemnation  that  he  pronounces  upon  all  tests  which  do 
not  involve  a  complete  solution  of  the  whole  of  the  quinine  sulphate 
during  the  operation,  though  I  admit  that  by  complete  solution  of 
the  material  tested  mixed  crystallizations  may  be  placed  on  the  same 
level  as  artificial  mixtures.  This  latter  result  may,  however,  be 
obtained  simply  by  allowing  the  mixture  to  effloresce  at  a  moderate 
temperature. 
In  reference  to  the  other  tests  that  have  recently  been  proposed, 
that  of  Kremel  may  be  mentioned  as  very  delicate,  but,  like  other 
titration  methods,  it  has  the  disadvantage  that  it  must  necessarily  be 
assumed  that  the  substance  examined  actually  contains  the  constituent 
that  is  to  be  determined  by  the  operation.  This  condition  cannot  be 
ensured  in  the  case  now  under  consideration ;  consequently  that 
method  of  testing  is  inapplicable  quite  independently  of  the  circum- 
stance that  when  the  commercial  quinine  sulphate  containing  cinchoni- 
dine sulphate  is  heated  with  hot  water,  as  Kremel  directs,  a  solution 
is  not  unfrequently  obtained  on  cooling  which  does  not  contain  the 
sulphates  in  question  in  the  same  proportions  as  water  solutions  of 
each  of  them  separately  would  do. 
The  bisulphate  test,  recommended  by  De  Vrij,  has  a  sounder  foun- 
dation, and  it  yields  very  good  results  when  it  is  carried  out  with  the 
