Am.  Jour.  Pharm.  "I 
May.  1888.  J 
Bismuth  lodide. 
25S 
anhydride.  Water  containing  much  organic  matter,  and  rich  in  car- 
bonic anhydride,  rapidly  corrodes  lead,  but  polished  surfaces  of  the 
metal  remain  perfectly  bright  when  immersed  in  pure  solutions  of 
organic  compounds,  such  as  starch  and  sugar,  provided  no  carbonic 
anhydride  is  present. 
BISMUTH  IODIDE. 
By  B.  S.  Gott,  B.A.,  and  M.  M.  Pattison  Muie,  M.A. 
It  is  known  that  bismuth  iodide,  Bilg,  may  be  prepared  either  by 
heating  together  bismuth  and  iodine  in  the  ratio  Bi :  31,  or  by  adding 
an  aqueous  solution  of  potassium  iodide  to  a  solution  of  bismuth 
nitrate  in  dilute  nitric  acid.  The  directions  given  by  earlier  experi- 
menters for  preparing  this  compound  in  the  wet  way  are  vague.  We 
have  recently  made  some  experiments  on  the  preparation  of  bismuth 
iodide,  and  also  on  the  comparative  stabilities  towards  water  of  this 
compound,  according  as  the  specimen  is  prepared  in  the  dry  or  the  wet 
way. 
Preparation  of  Bismuth  lodide  in  the  Wet  Way. — Excess  of  a  fairly 
concentrated  aqueous  solution  of  potassium  iodide  is  added  to  bismuth 
nitrate  dissolved  in  the  smallest  possible  quantity  of  dilute  nitric  acid ; 
Bilg  is  thus  precipitated  along  with  iodine.  The  precipitate  is  dis- 
solved in  as  small  a  quantity  as  possible  of  concentrated  aqueous 
hydriodic  acid,  and  water  is  added  until  the  greater  part  but  not  the 
whole  of  the  bismuth  is  precipitated  as  brown  Bilg.  The  solid  matter 
is  collected  and  dried  for  some  time  at  100°,  whereby  most  of  the  free 
iodine  is  volatilized.  The  residue  is  then  washed  once  or  twice  with 
absolute  alcohol,  and  finally  dried  at  100°. 
Some  Properties  of  Bismuth  lodide. — The  salt  prepared  as  described 
above  is  somewhat  soluble  in  alsolute  alcohol :  100  parts  by  weight 
of  alcohol  at  20°  dissolve  about  3|  parts  of  the  salt. 
The  sp.  gr.  of  Bilg  prepared  in  the  dry  way  was  found  to  be  5*64; 
20° 
and  the  sp.  gr.  of  Bilg  prepared  in  the  wet  way  to  be  5*65  at   — . 
20° 
Specimens  of  the  iodide  prepared  in  both  ways  were  treated  with 
water  in  about  the  ratio  Bilg :  SOOOHgO,  for  different  times  and  at 
different  temperatures ;  the  amount  of  decomposition  to  BiOI  and  HI 
