ON  DISTINGUISHING   QUININE  FROM  QUINIDINE.  453 
THE  MODE  OF  DISTINGUISHING  QUININE  FROM  QUINIDINE. 
TO  THE  EDITOR  OF  THE  PHARMACEUTICAL  JOURNAL. 
Sir, — Your  last  number  contains  a  report  of  a  lecture  delivered 
at  Liverpool  (before  the  Liverpool  Chemists'  Association)  by  Dr. 
Nevins,  in  which  the  lecturer  throws  doubts  upon  the  results  ob- 
tained by  previous  observers  with  quinine  and  quinidine.  The 
subject  is  not  necessarily  involved  in  obscurity,  and  in  order  to 
show  the  real  origin  of  his  difficulties  I  beg  to  submit  a  few  ob- 
servations. 
It  is  difficult  to  adapt  these  experiments  to  a  lecture-room  ;  for 
instance,  to  ascertain  the  extent  to  which  sulphate  of  quinine  is 
soluble  in  cold  water  requires  some  time.  If  the  water  is  cold, 
the  process  of  solution  goes  on  extremely  slowly  when  the  solution 
is  nearly  saturated.  Mr.  Barry's  plan  is  a  better  one  :  he  heats 
the  liquid  till  solution  is  effected,  and  then  by  cooling  obtains  a 
cold  saturated  solution,  with  a  few  minute  feathers  of  crystalliza- 
tion. I  think  we  must,  therefore,  leave  the  solubility  of  sulphate 
of  quinine  in  water  as  it  has  been  previously  settled.  A  more 
important  question  is  the  tests  for  quinine  and  quinidine,  founded 
upon  their  relative  solubility  in  ether,  or  in  water  as  sulphates. 
Dr.  Nevins  appears  to  have  taken  as  the  material  for  his  ex- 
periments a  substance  which  was  not  pure  quinidine.  He  found 
it  soluble  in  ten  parts  of  ether.  No  wonder,  therefore,  that  the 
tests  recommended  by  others  failed  or  only  partially  succeeded. 
In  order  to  obtain  satisfactory  results,  we  must  have  a  pure  article 
as  the  basis  of  experiments  ;  for  this  purpose  quinidine  should  be 
crystallized  twice  out  of  ether  ;  and  any  one  who  will  take  the 
trouble  to  do  this  will  find  the  old  observations  tolerably  accurate. 
It  is  much  easier  to  obtain  sulphate  of  quinine  free  from  quini- 
dine, than  sulphate  of  quinidine  free  from  quinine.  Two  or 
three  crystallizations  will  leave  the  quinidine  in  the  mother-liquors 
as  the  more  soluble  salt ;  but  if  we  now  attempt  to  crystallize 
out  the  sulphate  of  quinidine,  it  will  even  after  repeated  crystal- 
lizations contain  sulphate  of  quinine,  a  difficulty  familiar  enough 
to  chemists  in  purifying  a  more  soluble  salt  from  a  less  soluble. 
Consequently  commercial  sulphate  of  quinidine  always  contains 
some  quinine  more  or  less,  or  may  happen  to  contain  a  good  deal, 
though  of  course  the  manufacturer  will  not  purposely  sell  the 
