164 
Bismuthyl  Iodide. 
( Am.  Jour.  Pharm. 
\      April,  1889. 
hour,  were  found  to  contain  only  27 '6  per  cent,  iodine,  making  the 
resulting  compound  represent  76*66  per  cent.  BiOI,  with  a  large 
amount  of  BiON03.H20,  showing  conclusively  that  large  quantities  of 
KI  remained  undecomposed  and  were  lost  in  the  washings,  and  that 
there  is  nothing  "  definite  "  in  its  composition.  The  washings,  when 
tested  with  a  solution  of  AgN03,  gave  a  copious  white,  curdy  precipi- 
tate of  Agl. 
Several  samples  were  made  by  various  other  methods,  as  by 
"  trituration,"  etc.,  but  none  of  these  were  satisfactory,  having  various 
percentages  of  BiOI,  from  88  to  95  per  cent,  with  "uncertain" 
quantities  of  BiON03*H20,  differing  in  no  special  way  from  those 
already  spoken  of. 
Of  all  the  methods  so  far  considered  I  had  found  no  one  that  was 
entirely  satisfactory.  The  method  of  "precipitation"  seemed  to  be 
in  all  respects  better  than  any  of  the  others,  yet  it  was  far  from  being 
perfect.  In  experimenting  upon  this  process  I  found  that  it  should  be 
modified  as  follows :  Dissolve  409  grs.  BiOX03'H20  in  1  fluid  ounce 
HN03  with  the  aid  of  heat,  as  is  stated  in  Mr.  England's  formula  ; 
then  carefully  dilute  this  solution  with  water  as  long  as  BiOX03  is 
not  reprecipitated,  or,  at  least,  until  it  has  assumed  a  slight  permanent 
opalescence.  Add  to  this  221  grs.  of  KI,  dissolved  in  about  16  fluid  oz. 
of  cold  water,  in  a  large  flask  or  some  suitable  vessel,  agitate  thor- 
oughly, and  then  apply  heat,  but  not  to  the  boiling  jjoint,  (about 
80°-85°  C).  The  mixture  at  first  assumes  a  black  color,  growing 
gradually  brownish,  becoming  still  lighter  as  it  is  agitated,  and  under 
the  influence  of  moderate  heat  and  violent  agitation  it  is  finally 
changed  from  a  light  brown  to  a  brilliant  red.  The  agitation  is  con- 
tinued for  a  few  moments  longer  that  the  reaction  may  be  completed. 
The  precipitate  is  washed  by  decantation,  drained  upon  a  plain  filter 
and  dried  at  100°  C.  The  yield  should  be  about  470  grs.  The 
whole  operation  is  completed  in  a  very  short  while.  No  iodine  is 
liberated,  and  hence  the  product  contains  a  larger  and  proper  percent- 
age of  it,  and  represents  a  pure  article  of  BiOI. 
Bismuthyl  iodide  so  obtained  is  of  a  very  bright  red  color,  almost 
vermilion,  and  has  the  additional  advantage  of  being  in  very  fine 
powder,  light  and  bulky,  admirably  adapted  for  use  as  a  dusting 
powder  or  dressing,  an  advantage  possessed  by  none  of  the  other  speci- 
mens. By  analysis  I  found  it  to  contain  35'8  per  cent,  of  iodine, 
making  99'44  per  cent.  BiOI,  with  only  *35  per  cent.  BiOX03.H20. 
