334 
Thalleioquin  Reaction. 
Am.  Jour.  Pharm. 
May,  1921. 
obtained  in  quinine  solutions  of  greater  dilution  than  i :  iooo,  these 
results!  show  at  1 :  5000,  with  6  atoms  of  bromine,  a  decided  cloudi- 
ness ;  at  1 :  2500,  with  the  same  amount  of  bromine,  a  precipitate ;  at 
1 :  1750  this  precipitation  begins  at  0.75  atom,  is  distinct  at  2 :  25 
atoms,  and  increases  up'  to  the  addition  of  6  atoms  of  bromine. 
During  the  addition  of  ammonia,  at  dilutions  of  1 :  1000  to 
1 :500c,  a  pink  coloration  is  first  obtained,  which  appears  earlier  with 
increase  of  quinine  concentration ;  in  every  case,  when  the  solution  is 
alkaline,  this  coloration  changes  to  green  on  standing. 
With  increase  of  bromine,  at  dilutions  of  1  :iooo  to  1 :  5000, 
during  addition  of  ammonia,  white  fumes  appear,  which  with  in- 
crease of  quinine  appear  earlier  in  the  series ;  these  fumes  were 
noted  with  bromine*  present  to  the  extent  of .  about  0.023  g.  per  100 
C.  c.  of  solution  in  excess  of  the  6  atoms  per  quinine  molecule. 
Time  of  Action  of  Bromine  Before  Addition  of  Ammonia. — 
Experiments  were  now  made  to  find  the  influence  of  definite  inter- 
vals of  time  of  action  of  bromine  before  addition  of  ammonia,  the 
intervals  chosen  being  immediate  (five  seconds),  one  minute,  and 
five  minutes,  with  the  following  results :  with  immediate  action,  and 
addition  of  ammonia  till  the  solution  is  alkaline,  the  best  results  are 
obtained  with  stronger  solutions  down  to  1 : 40,000,  according  to 
the  amount  of  bromine  present ;  with  one-minute  action  weaker  solu- 
tions give  the  best  results ;  action  of  bromine  for  five  minutes  reduces 
the  resultant  color  strength,  but  in  the  weaker  solutions  (1:40,000 
downwards)  this  is  still  of  deeper  shade  than  with  the  correspond- 
ing dilutions  with  immediate  action. 
Color — Strength  Deterioration. — Trials  made  for  this  purpose 
showed  that  the  green  colour  fades  to  some  extent,  but  not  very  ma- 
terially, up  to  five  minutes. 
The  following  conclusions  are  drawn  from  the  above  results : 
(1)  Excess  of  bromine  and  its  prolonged  action  are  detrimental  to 
the  production  of  the  thalleioquin  reaction,  6  atoms  of  this  halogen 
for  one  minute  being  ample  for  strongest  color  depths;  (2)  with 
quinine  solution  1 :  1000  to  1 :  20,000  the  reaction  commences  in 
presence  of  0.75,  at  1 : 40,000  to  1 :  80,000  in  presence  of  1.5  to  2.25, 
at  1 :  120,000  in  presence  of  3,  and  at  1 :  200,000  in  presence  of  6 
