Am.  Jour.  Pharm.  ( 
May,  1921.  ( 
Thalleioquin  Reaction. 
333 
that  with  modification  and  practice  it  could  be  used;  LaWall  used 
from  io  to  40  atoms  of  bromine  from  potassium  bromate  and  hydro- 
bromic  acid  per  mol.  of  quinine.5 
From  the  figures  given  by  Trimble  and  Leger — the  only^data 
found  up  to  1909 — it  appeared  that  the  amount  of  halogen  used  was 
excessive  and  variable.  The  present  author  therefore  investigated 
the  reaction  to  determine  more  minutely  t  1)  the  exact  conditions 
necessary;  (2)  its  limit  of  sensitiveness,  and  (3)  if  it  were  possible 
to  brace  a  quantitative  method  on  it,  using  bromine  as  the  halogen.  ■ 
The  following  solutions  were  used:  (1)  Quinine  as  sulphate,  in  . 
dilutions  1:1000  to  1:200,000;  (2  )  bromine  water,  freshly  made, 
and  (3)  ammonia.  5  per  cent,  solution.  Preliminary  trials  showed 
that  the  shade  of  color  produced  depended  (  1).  on  the  quantity  of 
bromine:  (2)  time  of  action  of  bromine  before  addition  of  ammonia, 
and  i  3)  deterioration  of  color  by  standing  after  reaction  is  obtained. 
Quantity  of  Bromine. — In  all,  eleven  dilutions  were  treated  with 
increasing  amounts  of  bromine,  starting  with  0.75  and  increasing  by  ' 
0.75  up  to  12.75  atoms  per  mol.  of  quinine,  ammonia  being  added 
after  similar  times  of  actions,  the  solutions  made  up  to  a  total  vol- 
ume of  25  c.  c.  or  2*4  inches  in  the  tube,  and  the  color  shade  noted, 
with  the  following  results : 
With  quinine  solutions  1  :  1750  or  stronger,  and  with  6  or  more 
atoms  of  bromine  per  mol.  of  quinine,  before  ammonia  addition,  a 
yellow  precipitate  is  obtained. 
Y\  ith  increase  of  bromine  and  addition  of  ammonia  the  color 
proceeds  from  blue,  blue-green  to  yellow-green  and  yellow;  finally 
this  yellow  disappears,  except  in  solutions  1  :  5000  or  stronger. 
The  strongest  color  depth  is  obtained  with  6  atoms  of  bromine 
shown  consecutively  in  dilutions  1 :  1750  to  1  :  1,200,000;  at  1  :  1000 
this  maximum  appears  somewhat  earlier  with  5.25  atoms  of  bromine, 
but  the  difficulty  of  comparing  colors  of  precipitates  may  account 
for  this. 
The  stronger  the  quinine  solution,  the  earlier  does  the  yellow 
shade  of  green  appear :  at  1  :  1000  to  1  :  10.000  it  appears  before  and 
extends  longer  in  the  series  after  the  maximum  color  is  attained. 
Contrary  to  a  published  statement  that  no  green  precipitate  is 
'LaWall,  Amer.  J.  Pharm.,  1904,  281. 
