NEW  TEST  FOR  QUININE. 
517 
though,  consequently,  convinced  of  the  correctness  of  my  obser- 
vation, I  have,  nevertheless,  again  undertaken  the  subject,  to  be 
able  to  learn  the  relations  which  have  caused  the  failures  in 
other  hands.  Believing  that  error  lay  in  the  quinine  itself,  I 
have  examined  several  kinds  of  quinine  derived  from  various 
sources,  and  obtained  the  reaction  with  all ;  the  failure  of  the  re- 
action must,  therefore,  be  sought  for  in  the  method.  By  a  se- 
ries of  researches  it  has  been  shown  that,  as  was  expected,  the 
prevention  of  success  is  caused  by  the  constitution  of  the  reagents, 
the  chlorine  water,  and  the  ferrocyanide  of  potassium.  The 
chlorine  water  must  be  necessarily  concentrated,  freshly  prepared 
and  free  from  muriatic  acid.  If  the  solution  of  ferrocyanide  of 
potassium  is  not  concentrated  by  solution  in  the  heat,  the  red 
coloration  appears  later,  but  can  be  obtained  directly,  and  also 
with  a  diluted  solution  of  ferrocyanide  of  potassium,  upon  the 
addition  of  a  few  drops  of  ammonia ;  the  failure  also  depends 
upon  the  quantities  of  the  reagents.  Only  a  proportionately 
small  quantity  of  the  chlorine  water  must  be  taken ;  on  the  con- 
trary, a  large  excess  of  the  solution  of  ferrocyanide  of  potassium, 
if  it  be  desirable  not  to  add  a  little  ammonia,  I  have  further 
remarked  that  an  aqueous  solution  of  sulphate  of  quinine  is  to  be 
preferred  to  a  spirituous  one,  because  the  spirituous,  when  not 
sufficient  chlorine  water  is  present,  precipitates  the  concentrated 
solution  of  ferrocyanide  of  potassium,  and  the  establishment  of 
red  coloration  is  thereby  rendered  difficult.  It  needs  be  scarce- 
ly mentioned  that  the  reagents  must  be  applied  in  the  prescribed 
order,  as  in  any  other  way  no  reaction  appears. 
I  now  give  the  following  method  by  which  this  reaction  can 
be  obtained,  under  all  circumstances,  by  the  most  inexperienced. 
Sulphate  of  quinine  is  introduced  into  a  test  tube,  and  water 
poured  on  it,  so  that  the  greater  part  of  the  crystals  remain  un- 
dissolved. Some  drops  of  this  fluid,  which  is  shaken  to  regain 
the  sulphate  of  quinine  on  suspension,  are  poured  into  a  watch 
glass,  and  so  much  chlorine  water  added  that  a  clear,  somewhat 
yellowish,  solution  results.  The  quantity  of  chlorine  water  ap- 
plied depends  upon  its  concentration,  and  upon  the  quantity  of 
quinine  salt.  When  into  this  chlorinated  quinine  solution  finely 
pulverized  ferrocyanide  of  potassium  is  introduced,  it  acquires  a 
bright  rose  red  color.  The  rose  red  color  passes  over  soon,  and 
particularly  rapidly,  if  still  more  of  the  pulverized  ferrocyanide 
