566  On  Some  of  the  Tests  for  Quinine.    { A£ct^J,imm' 
delicate  than  that  of  chlorine,  since  under  it  a  green  coloration 
might  be  obtained  from  a  i-20000th  solution  of  quinine,  whereas, 
chlorine  had  its  limit  in  about  a  i-5000th  solution. 
In  the  following  examinations  a  saturated  aqueous  solution  of 
bromine  was  employed,  it  being  prepared  by  agitating  excess  of 
bromine  with  water,  and,  after  subsidence,  decanting  the  clear, 
highly  colored  solution.  The  reagent  should  be  freshly  prepared, 
since  it  may,  within  twenty-four  hours,  especially  if  exposed  to 
light,  undergo  a  marked  change.  A  saturated  aqueous  solution  of 
the  reagent  contains  practically  I  per  cent,  by  volume,  or  3  per  cent, 
by  weight  of  bromine. 
A.    i-iooth  solution  of  quinine. 
1.  5  c.c.  of  the  solution  yields  with  : 
(a)  One  drop  of  bromine  water  :  a  copious  yellow  pre- 
cipitate which  quickly  dissolves  to  a  colorless  solution, 
the  addition  of  a  drop  of  ammonia  causes  a  white  precipi- 
tate (quinine),  which,  after  a  time,  acquires  a  bluish  hue, 
then  a  bluish  green  color. 
(£)  Three  drops  bromine  water  then  one  drop  ammonia, 
yield  a  precipitate  which  soon  assumes  a  greenish  blue  color. 
(c)  0  5  c.c.  bromine  water  followed  by  one  drop  ammonia  : 
the  mixture  quickly  becomes  bluish  green,  which  increases 
its  intensity. 
(d)  I'D  c.c.  bromine  water  causes  a  slightly  yellow  color- 
ation ;  the  addition  of  01  c.c.  ammonia  produces  a  white 
precipitate  which  quickly  assumes  a  bright  green  color, 
which  may  change  to  purple. 
The  exact  coloration  produced  in  the  above  solutions  depends 
somewhat]  upon  the  manner  in  which  the  reagents  mix  with  the 
quinine  solution.  The  best  results  are  obtained  by  dropping  the 
reagents  into  the  quinine  solution  without  agitation. 
2.  I  c.c.  of  the  quinine  solution  yields  with  one  drop  of  ammonia 
after  addition  of : 
(a)  One  drop  bromine  water  :  a  white  precipitate  which 
soon  assumes  a  green  color. 
(b)  0-2  c.c.  bromine  water:  quickly  a  bright  green  solution. 
'(c)  0  5  c.c.  bromine  water:  a  purple  precipitate,  which, 
after  a  time,  assumes  a  strong  green  color. 
