Am.  Jour.  Pharm. 
March,  1887. 
Bismuth  Oxyiodide. 
121 
The  process  is  a  tedious  and  expensive  one,  and  is  only  given  to 
prove  that  the  repeated  action  of  KI  and  HC2H302on  (BiO)2C02  will 
give  a  pure  oxyiodide. 
The  pure  salt,  BiOI,  was  obtained  by  the  action  of  HI  on  (BiO)2 
COs.  Hvdriodic  acid  was  made  by  the  action  of  H2S  on  I,  in  presence  of 
water ;  after  the  complete  conversion  of  I  into  HI,  the  solution  is  boil- 
ed until  the  aqueous  vapor  no  longer  darkens  acetate  of  lead  paper.  To 
this  solution  is  then  added  the  oxycarbonate  in  small  consecutive  por- 
tions. It  is  first  dissolved  to  a  yellowish-red  solution,  C02  being  lib- 
erated, and  then  on  further  addition  there  is  precipitated  the  normal 
iodide  Bil3.  This  is  changed  by  boiling  with  the  (BiO)2COs  into  BiOI. 
There  is  no  difficulty  in  avoiding  an  excess  of  the  oxycarbonate  if  the 
color  of  the  supernatant  liquid  be  watched,  for  as  long  as  it  is  colored 
there  is  present  free  hvdriodic  acid.  The  addition  of  (BiO)2C03  must 
cease  as  soon  as  the  liquid  assumes  a  pale  yellow  color  (Spec.  CI).  The 
product  yields  66*40  per  cent.  Bi2Os.    The  reactions  are  as  follows  : 
2  H2S+2I2=4  HI+S2. 
(BiO)2C03+6  HI=2  BiI3-3  H20-C02. 
BiI3+(BiO)2C03=3  BiOI-C02. 
Every  atom  of  iodine  is  converted  into  one  molecule  of  BiOI.  To 
make,  for  example,  30  gm.  BiOI,  10*77  gm.  iodine  and  22*55  gm. 
oxycarbonate  of  bismuth  are  required.  For  the  preparation  of  it,  there 
may  be  taken  one  part  iodine  and  two  parts  oxycarbonate,  which  will 
give  almost  three  parts  BiOI.  The  preparation  thus  obtained  has  a 
copper-red  or  chocolate  color,  is  crystalline,  soluble  in  strong  HC1  with- 
out liberation  of  I ;  HXOa  liberates  iodine,  forming  Bi(X03)3.  Dilute 
acids  decompose  it,  forming  Bil3  and  the  corresponding  salt.  The 
action  of  dilute  sulphuric,  for  instance,  is : 
3  BiOI -3  H2SO,=BiI3-Bi23  S04-f  3H20. 
BiOI  was  obtained  by  Schneider  (Watts'  Dictionary)  by  heating 
Bil3  in  air.  It  can  also  be  obtained  by  boiling  the  normal  iodide  with 
a  large  excess  of  water.  BiI3+H20=BiOI-f-(HI)2.  This  is  a  costly 
method,  as  two-thirds  of  the  iodine  present  is  liberated  as  hvdriodic 
acid,  holding  in  solution  some  of  the  bismuth.  (Spec.  C2.) 
A  sample  of  oxyiodide  (Spec.  C3)  is  presented,  made  by  concen- 
trating the  hvdriodic  acid,  liberated  as  above,  and  adding  oxycarbonate. 
The  three  specimens  of  pure  oxyiodide  are  identical  in  appearance 
and  properties.  CI,  however,  is  in  larger  crystals,  due  perhaps  to  the 
fact  that  the  hydriodic  acid  used  was  more  concentrated  than  that  from 
which  Spec.  C3  was  prepared. 
