Am.  Jour.  Pharm. 
May,  1889. 
Bismuth  Oxyiodide. 
237 
not  only  for  the  preparation  of  the  oxyiodide  but  also  for  the  com- 
position of  bismuth  subnitrate. 
I  have  examined  the  process  of  Mr.  Greene  and  will  call  attention 
to  a  few  points :  In  making  his  calculations,  the  formula  for  the 
subnitrate  is  given  as  BiON03H20.  As  the  commercial  salt  in- 
variably contains  bismuth  oxide,  the  solution  in  nitric  acid  will 
contain  more  Bi(jS"03)3  than  can  be  decomposed  by  the  KI  used, 
hence,  should  the  product  require  all  of  the  KI  there  is  danger  of 
oxynitrate  being  precipitated  with  the  oxyiodide.  Again,  the  free 
nitric  acid  will  under  the  most  favorable  conditions  keep  in  solution 
considerable  bismuth  nitrate,  possibly  the  above  excessive  amount ; 
under  unfavorable  conditions  iodine  may  be  liberated  and  thus  loss 
entailed  in  either  case. 
In  following  his  directions,  after  the  addition  of  the  KI  solution 
to  the  diluted  bismuth  solution,  and  warming  the  evolution  of  iodine 
vapors  occurred,  on  immersing  a  thermometer  the  temperature  60°  C. 
was  registered.  A  second  experiment  confirmed  this ;  the  tempera- 
ture given  in  the  paper  is  80-85°.  If  this  decomposition  takes  place 
the  product  is  washed  with  difficulty,  the  filtrate  contains  considerable 
bismuth  and  iodine.  To  obtain  a  specimen  for  analysis  which  was 
not  decomposed  by  excessive  heat,  another  trial  was  made  and  this 
time  the  temperature  kept  at  50°  for  ten  minutes ;  after  no  further 
change  in  color  could  be  noticed,  it  was  filtered,  washed,  dried  and 
weighed. 
The  yield  was  above  the  theoretical  quantity,  being  102.1  per  cent, 
instead  of  100.  The  filtrate  gave  only  a  cloudiness  with  AgN03,  but 
a  very  decided  precipitate  with  KOH.  The  preparation,  compared 
with  my  own,  was  of  almost  the  same  color,  a  trifle  more  red,  and  was, 
as  expected,  a  little  bulkier ;  on  ignition  it  left  66.80  per  cent.  Bi20,3 
pure  BiOI  should  leave  66.36  per  cent.,  which  would  indicate  the  fol- 
lowing composition  :  oxyiodide,  97.05  per  cent.,  oxynitrate,  2. 95  per. 
cent.  Owing  to  the  variable  nature  of  the  subnitrate,  there  can  be  no 
process  devised  which  will  require  the  exact  amounts  of  subnitrate  and 
potassium  iodide,  hence,  in  all  cases  there  must  be  an  excess  either  of  the 
subnitrate  or  the  potassium  iodide  ;  the  latter  is  preferred  by  me  because 
it  will  prevent  contamination  with  subnitrate,  and  allow  one  to  test 
the  completeness  of  the  washing  of  the  oxyiodide.  The  nitric  acid 
used  in  my  process  is  so  slight  after  the  saturation  of  the  Bi203  that 
it  will  not  decompose  the  slight  excess  of  KI. 
