5^2  On  Some  of  the  Tests  for  Quinine.  {^£{£$8?' 
decomposition  of  the  quinine  which  varied  with  the  amount  of 
chlorine  employed,  and  thus  determined  whether  a  green  precipitate 
would  be  produced,  or  the  liquid  simply  acquire  a  green  color  or 
become  yellow. 
The  green  precipitate  thus  produced  was  found  to  have  a  bitter 
taste  similar  to  that  of  quinine ;  was  insoluble  in  cold  water  and 
only  sparingly  soluble  in  boiling  water;  insoluble  in  ether,  but 
readily  soluble  in  alcohol,  and  readily  soluble  in  diluted  acids  form- 
ing red  solutions,  from  which  it  was  reprecipitated  of  a  green  color 
on  neutralizing  the  solution  with  ammonia. 
In  1853,  A.  Vogel1  proposed  to  modify  this  test  by  treating  the 
quinine  solution  after  addition  of  chlorine  water,  with  a  solution  of 
potassium  ferrocyanide  and  then  adding  a  few  drops  of  ammonia, 
when  the  mixture  would  assume  a  deep  red  color,  the  green  color 
not  appearing. 
Professor  Fliickiger,  in  1861,  confirmed  the  observation  of  Vogel 
and  found  that  the  same  red  coloration  might  be  produced  by  sub- 
stituting potassium  ferricyanide  for  the  ferrocyanide. 
More  recently,  Chas.  F.  Zeller2  has  examined  this  test  in  regard 
to  the  production  of  a  green  coloration  under  the  action  of  chlorine 
and  ammonia,  and  confirmed  the  observations  of  Brands,  namely: 
that  the  results  were  influenced  by  the  relative  proportion  of  the 
substances  employed. 
It  being  thus  shown  that  this  test  was  much  influenced  by  the 
relative  proportions  of  quinine  and  chlorine  present,  the  following 
investigations  were  made  for  the  purpose  of  more  definitely  deter- 
mining the  range  within  which  the  green  coloration  would  manifest 
itself  in  different  quantities  of  the  same  solution,  and  in.  solutions 
of  different  degrees  of  dilution. 
The  quinine  was  employed  in  solution  both  as  sulphate  and  hydro- 
chloride, the  i-iooth  solutions  being  prepared  by  dissolving,  by  the 
aid  of  just  sufficient  of  the  diluted  acid  to  effect  solution,  1  gramme 
of  the  pure  alkaloid  in  100  c.c.  of  water.  The  more  dilute  solutions 
were  prepared  from  the  i-iooth  solutions,  by  the  required  dilution 
with  water. 
The  chlorine  water  consisted  of  a  saturated  aqueous  solution  of 
1  This  Journal,  1853,  516. 
2 See  Ibid.,  1880,  385. 
