^Dec^'ilS^111}    Fluorescences  of  Manganese  and  Bismuth.  615 
Archives  de  Phar.,  Nov.  5,  1887),  after  researches  made  with  minute 
precautions,  have  concluded  that  the  skin  does  not  absorb  metallic 
mercury,  although  it  may  take  up  its  salts.  The  mercury  of  inunc- 
tions, so  they  believe,  becomes  volatilized,  and  is  absorbed  through 
the  respiratory  organs. 
FLUOKESCENCES  OF  MANGANESE  AND  BISMUTH.1 
By  L.  de  Boisbaudran. 
The  author  has  continued  his  researches,  and  has  examined  the  fluo- 
rescences of  a  mixture  of  two  solid  solvents  behaving  towards  one  an- 
other as  moderately  active  substances,  and  a  third  substance  strongly 
fluorescent  with  one  of  the  solvents  only,  as  represented  by  a  mixture 
of  cadmium  sulphate  (100  parts),  bismuth  sulphate  (10  parts),  and 
calcium  sulphate.  With  a  proportion  of  calcium  sulphate  not  exceed- 
ing 14*8  per  cent.,  the  calcium  cadmium  fluorescence  is  prevented  by 
the  presence  of  bismuth,  although  the  calcium  bismuth  fluorescence  is 
not  visible.  When  the  quantity  of  calcium  sulphate  exceeds  16*1  per 
cent.,  the  calcium  bismuth  fluorescence  becomes  visible,  and  increases 
in  brilliancy  with  the  proportion  of  calcium  sulphate. 
The  author  has  also  investigated  the  properties  of  a  mixture  of  two 
solid  solvents,  the  first  of  which  (a)  behaves  towards  the  second  (/9)  as 
a  moderately  active  substance,  and  two  active  substances,  one  of  which 
fluoresces  with  both  solvents,  and  the  other  with  only  one  of  them. 
These  conditions  are  fulfilled  by  a  mixture  of  calcium,  cadmium,  bis- 
muth and  manganese  sulphates.  With  an  excess  of  calcium  sulphate 
the  calcium  manganese  fluorescence  is  strongest,  the  calcium  bismuth 
fluorescence  much  weaker,  and  the  cadmium  manganese  fluorescence  is 
not  visible.  With  an  excess  of  cadmium  sulphate,  the  cadmium 
manganese  fluorescence  is  predominant,  the  calcium  manganese  fluo- 
rescence is  also  visible,  but  the  calcium  bismuth  fluorescence  cannot 
be  recognized. 
The  author's  experiments  lead  to  the  following  general  conclusions  : 
A  substance  may  show  strong  fluorescence  when  disseminated  through 
another  substance,  and  yet  show  no  fluorescence  with  a  third  sub- 
stance closely  analogous  to  the  second.    A  substance  may  fluoresce 
1Compt.  rend.,  105,  45-48  and  206-208.  Keprinted  from  Jour.  Chem.  Soc, 
November. 
