ADecemberia89r }   On  Some  of  the  Tests  for  Quinine.  571 
(2)  i-ioooth  solution,  a  strongly  marked  fluorescence  in  reflected 
light ;  only  feebly  marked  in  direct  sunlight ;  but  intense  in  a  cone 
of  sunlight. 
(3)  i-fooooth  solution,  a  just  perceptible  fluorescence  in  reflected 
light ;  appears  colorless  in  sunlight ;  intensely  fluorescent  in  a  cone 
of  sunlight. 
(4)  1 -50000th  solution  exhibits  no  marked  fluorescence  in  either 
reflected  or  in  direct  sunlight,  and  only  a  faint  fluorescence  under  a 
cone  of  sunlight.  On  the  addition  of  a  drop  of  dilute  sulphuric 
acid,  the  solution  presents  a  quite  well-marked  fluorescence  in  con- 
densed sunlight. 
(5)  i-ioooooth  solution  in  condensed  sunlight  presents  only  a 
faint  fluorescence ;  but  on  addition  of  a  drop  dilute  sulphuric  acid, 
the  fluorescence  is  well  marked. 
The  last-mentioned  degree  of  dilution  is  by  no  means  the  limit  of 
the  fluorescence  of  quinine  solutions,  under  certain  conditions. 
Kerne,  rby  a  specially  constructed  instrument,  termed  by  him  the 
fluorescope,  was  able  to  obtain  the  fluorescence  beautifully  marked 
in  a  solution  of  the  alkaloid  under  a  dilution  of  two  million  times. 
It  should  be  borne  in  mind  that  the  fluorescence  of  quinine  solu- 
tions, even  of  the  sulphate,  may  be  entirely  prevented  by  the  pre- 
sence of  chlorides,  bromides  and  iodides,  and  the  free  acids  of  these 
salts.  If  to  1  c.c.  of  a  i-iooth  solution  of  quinine  sulphate,  which 
is  strongly  fluorescent,  one  drop  of  hydrochloric  acid  or  of  a  solution 
of  sodium  chloride  (1  :  10),  be  added,  the  fluorescence  is  imme- 
diately and  wholly  destroyed,  and  is  not  reproduced  on  the  addition 
of  even  0  5  c.c.  of  dilute  sulphuric  acid.  The  interference  of  bromine 
and  iodine  is  as  prompt  and  complete  as  that  of  chlorine. 
According  to  the  recent  observations  of  MM.  Sestini  and  Cam- 
pani1  the  fluorescence  of  sulphuric  acid  solutions  of  quinine,  especi- 
ally when  dilute,  may  also  be  concealed  by  the  presence  of  phenace- 
iine.  According  to  these  observers,  this  substance  may  also  greatly 
interfere  with  the  normal  reaction  of  quinine  with  both  chlorine 
and  bromine  in  the  thalleioquin  test. 
The  property  of  fluorescence  is  possessed,  although  in  a  less 
degree,  by  some  of  the  other  cinchona  alkaloids;  and  Dr.  Bence  Jones, 
of  London,  has  described  a  substance  normally  present  in  the  body, 
which  has  a  similar  property,  and  named  by  him  animal  quinoidine. 
1  Jour.  Chem.  Soc,  Abs.,  May  1892,  665. 
