234 
ON  QUINIDINE. 
cinchonidine  and  quinidine,  my  own  observations  have  shown 
me  that  the  greater  part  of  the  so-called  quinidine  met  with  in 
trade  has  been,  until  recently,  nothing  else  than  cinchonidine 
containing  more  or  less  quinine.  Thus,  for  instance,  in  the 
Paris  Exhibition  of  1855,  there  were  several  samples  of  so-called 
quinidine,  and  of  its  compounds,  but  I  found  them  to  be  all 
mainly  cinchonidine. 
I  am  indebted  to  Mr.  John  Eliot  Howard  for  having  first  sup- 
plied me  with  genuine  quinidine,  perfectly  pure  :  soon  after  I 
had  become  acquainted  with  its  properties,  my  friend  M.  Delondre 
also  sent  me  several  samples  of  true  quinidine,  in  a  state  of 
greater  or  less  purity.  The  quinidine  of  Mr.  Howard  was  so 
pure,  that  I  found  the  same  rotatory  power  as  Pasteur,  viz. 
Although  I  am  still  occupied  with  the  investigation  of  quini- 
dine and  the  other  cinchona-alkaloids,  which  investigation  is  not 
yet  completed,  I  will  not  delay  making  known  one  property  of 
quinidine  by  which  it  differs  widely  from  the  other  three  cinchona- 
alkaloids,  because  the  knowledge  of  this  property  may  be  useful 
for  the  successful  separation  of  quinidine  from  its  cognate 
alkaloids. 
Quinidine  forms  with  hydriodic  acid  a  salt  which  is  very  diffi- 
cultly soluble.  One  part  of  neutral  hydriodate  of  quinidine  re- 
quires 1250  parts  of  water  at  60°  F.  for  its  solution.  The  acid 
hydriodate  is  much  more  soluble,  for  one  part  is  dissolved  by  90 
parts  of  water  at  60°  F.  By  this  difficult  solubility  of  its  neutral 
hydriodate,  the  presence  of  quinidine  can  easily  be  detected.  I 
was  enabled  by  this  reaction,  together  with  the  observation  by 
polarized  light,  to  prove  undoubtedly  that  the  so-called  ft  Quinine 
of  Van  Heyningen  is  nothing  else  than  quinidine.  A  few  grains 
of  ft  Quinine  prepared  by  the  late  M.  Van  Heyningen  himself, 
enabled  me  to  prove  this  fact. 
Although  the  sulphate  of  quinidine  is  sparingly  soluble  in  cold 
water,  the  solution  is  nevertheless  very  strongly  precipitated  by 
a  solution  of  iodide  of  potassium.  I  have  no  doubt  that  the 
manufacturers  of  quinine  will  be  able  by  using  this  reaction,  to 
find  quinidine  in  many  specimens  of  the  so-called  quinoidine  or 
amorphous  quinine,  or,  at  least,  in  the  mother-liquors  obtained 
