12 
Bismuth  Subiodide. 
Am.  Jour.  Pharm. 
Jan.,  1887. 
the  gradual  addition  of  dilute  nitric  acid  (U.  S.  P.,  ?80)  all  the  bismuth 
salts  were  converted,  first,  into  the  black  iodide,  and  then  by  the  hot 
water  present  into  the  red  oxyiodide.  If  great  purity  is  desired,  the  addi- 
tion of  hot  water  could  be  omitted  and  the  suggestion  of  Prof.  Maisch  1 
be  employed,  namely :  that  to  obtain  the  oxyiodide  pure,  the  unwashed, 
dried,  precipitated  brown  (black  ?)  iodide  should  be  dissolved  in  hydri- 
odic  acid  or  in  potassium  iodide  and  precipitated  with  water.  He  fur- 
ther stated  that  the  black  bismuth  iodide  can  be  made  by  subliming  a 
mixture  of  iodine  and  powdered  bismuth,  whereby  black  metallic  scales 
of  the  iodide  are  obtained,  which  are  permanent  in  the  air,  but  little 
affected  by  cold  water  and  quickly  converted  by  hot  water  into  the  red 
oxyiodide.  It  may  be  here  mentioned,  in  connection  with  the  "  tritu- 
ration process,"  previously  described,  that  the  addition  of  the  dilute 
acid  should  not  be  pushed  beyond  the  point  where  all  the  bismuth  salts 
are  decomposed,  because  the  product  becomes  darker  than  its  normal 
color,  with  the  setting  free  of  iodine  and  the  formation  of  varying 
quantities  of  black  triodide,  which  latter,  however,  may  easily  be 
rechanged  to  the  oxyiodide  by  treatment  of  the  precipitate  with  water. 
The  whole  reaction,  accepting  the  U.  S.  P.  (1880)  formula  for  bismuth 
subnitrate,  may  be  summed  up  as  follows : 
BiON3    H20    +    KIO      =    BiOI   +     KN03    +  H20 
306  165-6  3526  101  18 
The  following  is  the  formula  employed,  using  four  times  the  mole- 
cular weight  in  grains : 
Take  of 
Bismuth  subnitrate,  %  iiss,  gr.  xxiv. 
Water  (hot),  f^viii. 
Potassium  iodide,       3  xi.  gr.  iii 
Dilute  Nitric  acid,  q.  s.  or  about  fgvi. 
Triturate,  in  a  mortar,  the  bismuth  compound,  with  the  potassium 
iodide  dissolved  in  the  hot  water,  and  then  slowly  add,  with  constant 
trituration,  f5iv  of  the  dilute  acid,  and  the  remainder,  drop  by  drop, 
until  the  decomposition  is  complete.  Filter;  wash  the  precipitate 
thoroughly  with  warm  water  until  the  washings  cease  to  alfect  blue 
litmus-paper ;  dry,  and  powder.  The  yield  is  about  three  troy 
ounces,  whose  cost,  counting  the  ingredients  of  manufacture  at  market 
rates,  is  inside  of  $3.50  a  pound  (av.)  or  25  cents  an  ounce  (av.), 
instead  of  $12  a  pound  (av.)  or  75  cents  an  ounce  (av.). 
Amer.  Jour.  Pharm.  December,  1886,  p.  599. — Bismuth  Oxyiodide. 
