AmjJneriSiarm"}    Atropine  Periodides  and  Iodomercnrates.  295 
investigated.  Jorgensen3  has  obtained  and  described  two  periodides 
of  atropine;  a  tri-iodide  and  a  pentaiodide.  Our  experience  has 
taught  us  that  in  aqueous  solutions  the  capacity  of  atropine  for 
combining  with  iodine  varies  very  widely,  and  the  quantities  taken 
up  seem  to  depend  upon  the  concentration  of  the  liquids  and  even 
the  order  of  mixing  them. 
The  highest  number  of  iodine  atoms  which  a  molecule  of  atropine 
can  combine  with  seems  to  be  nine ;  between  this  and  the  above- 
mentioned  tri-iodide  lie  the  other  compounds  of  atropine  with 
iodine  which  are  formed  in  aqueous  solution.  The  same  is  true 
when  chloroform  is  used  as  a  solvent.  We  reserve  for  a  later  date 
a  report  upon  the  exact  conditions  which  are  necessary  for  the  for- 
mation of  any  particular  periodide  of  atropine.  For  the  present  we 
wish  to  say  that  under  the  conditions  described  below  we  were  able 
to  obtain  the  enneaiodide  of  atropine,  C17H23N03  H1.I8,  as  the  sole 
combination  of  all  the  alkaloid,  and  sufficiently  stable. 
These  conditions  are  the  following  :  The  concentration  of  the 
aqueous  solution  of  the  atropine  salt  should  not  exceed  five-tenths 
per  cent.;  that  of  the  iodine  solution  must  not  exceed  one  per  cent.; 
the  latter  has  to  be  acidulated  with  some  sulphuric  or  hydrochloric 
acid;  the  atropine  solution  must  be  added  to  the  iodine  solution 
and  not  vice  versa,  and  this  addition  must  take  place  in  small  por- 
tions at  a  time,  shaking  the  mixture  thoroughly  after  each  addition. 
At  first  the  liquid  becomes  very  turbid  and  particles  of  iodine  are 
seen  to  be  floating  upon  its  surface  ;  on  continued  addition  of  the 
atropine  solution  and  shaking,  the  iodine-colored  turbidity  disap- 
pears, a  dark  granular  precipitate  falls  out,  and  the  supernatant 
liquid  becomes  perfectly  transparent,  but  is  still  dark-colored.  If 
the  addition  of  the  atropine  be  stopped  at  this  stage,  i.  e.}  while  the 
supernatant  liquid  has  a  very  dark  red  color,  the  composition  of  the 
precipitate  will  be  found  to  be  that  of  the  enneaiodide  C17Ho3N03HI.I8. 
Whether  additional  quantities  of  atropine  will  make  the  precipi- 
tate take  up  more  atropine  and  become  a  lower  periodide  we  shall 
try  to  determine  by  later  experiments.  On  the  other  hand,  when 
the  order  is  reversed  and  the  iodine  solution  is  added  to  the  atropine 
solution,  it  is  always  a  lower  periodide  that  is  formed  ;  but  whether 
on  continued  addition  of  the  iodine  the  precipitate  will  take  up 
more  of  it  and  become  a  higher  periodide,  we  cannot  say  as  yet. 
1  J.prakt.  Chem.,  2,  3,  329. 
