Am.  Jour.  Pharm.  1 
March,  1887.  J 
Kerners'  Quinine  Test. 
139 
timately  mixed  up.  When  the  mixture  is  heated  gradually  the  pro- 
portion of  quinine  sulphate  dissolved  goes  on  increasing,  and  a  larger 
quantity  of  the  cinchonidine  sulphate  passes  into  solution  in  such  a 
manner  that,  from  the  circumstance  of  the  two  salts  being  mixed  in 
the  crystals,  the  quantities  dissolved  of  each  are  correlative.  The  vol- 
ume of  water  used  being  insufficient  for  dissolving  even  at  100°  C. 
the  whole  of  the  quinine  sulphate,  a  very  notable  part  of  the  impuri- 
ties will  also  remain  undissolved,  and  not  come  within  the  scope  of 
the  subsequent  operations.  By  cooling  the  solution  to  15°  C.  almost 
the  whole  of  the  quinine  sulphate  crystallizes  out,  taking  with  it 
some  of  the  cinchonidine  salt ;  but  the  greater  part  of  this  latter  salt 
remains  in  solution.  The  quantity  of  cinchonidine  salt  transferred 
to  the  solution  is  thus  increased  in  proportion  as  the  heating  is  aug- 
mented. It  can  easily  be  ascertained  that  this  is  what  happens,  by- 
making  several  tests  with  the  same  sample  of  impure  quinine  sulphate, 
and  applying  different  temperatures  for  the  solution.  It  will  thus  be 
found  that  the  volume  of  ammonia  necessary  for  redissolving  the  bases 
liberated  will  be  increased  in  proportion  as  the  temperature  applied  is 
higher.  This  -may  also  be  ascertained  by  comparing  the  weights  of 
the  dry  residues  left  on  evaporating  equal  volumes  of  the  solutions  ob- 
tained when  different  degrees  of  heat  are  applied  in  the  testing  oper- 
ation. M.  Marty  has  in  this  way  shown  that  the  quantity  of  the  res- 
idue is  greater  in  proportion  as  the  heating  is  greater. 
In  short,  the  delicacy  of  the  test  is  so  much  greater  as  the  solution 
is  made  at  a  higher  temperature,  and  the  selection  of  a  particular  tem- 
perature should  be  regulated  according  to  the  greater  or  less  demand 
for  proof  of  purity  in  the  official  quinine  sulphate. 
It  has  also  been  said  that  this  mode  of  testing,  when  carried  out 
with  heat,  involve*  the  demand  for  an  exaggerated  degree  of  purity  in- 
compatible with  the  industrial  production  of  quinine  sulphate.  One 
of  the  experiments  cited  above  is  sufficient  to  prove  the  contrary.  It 
will  be  remembered  in  fact  that  pure  quinine  sulphate,treated  with  warm 
or  even  boiling  water,  gives  a  solution,  5  cc.  of  which,when cooled  to  15° 
C.  became  quite  clear  on  addition  of  about  5'5  cc.  of  arnnionia  solu- 
tion (0'96).  But  the  Codex  does  not  require  this  result  to  be  produced 
by  less  than  7  cc.  of  ammonia  solution  ;  the  difference  of  1*5  cc,  or 
more  than  one-fifth  of  the  whole  quantity,  being  available  for  the  so- 
lution of  bases  other  than  quinine  in  the  event  of  their  being  present. 
This  di fl'erence  represents  therefore  the  tolerance  of  the  prescribed  test. 
