THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
AUGUST,  1887. 
SOME  OFFICIAL  AND  NON-OFFICIAL  IODIDES. 
By  R.  Rother. 
For  sufficient  reasons  the  Pharmacopceia  has  omitted  the  submis- 
sion of  processes  for  the  preparation  of  various  official  chemicals ; 
hence  casual  and  occasional  operators  in  this  line  are  sometimes  de- 
pendent on  their  own  resources  for  the  adaptation  of  formulas  suitable 
to  their  wants.  The  origin  of  the  following  processes  is  of  this 
nature : 
Plumbic  iodide. — According  to  a  formerly  official  process  plumbic 
iodide  was  prepared  by  mixing  certain  proportions  of  plumbic  acetate 
and  potassic  iodide  in. aqueous  solution.  The  writer  has  usually  em- 
ployed this  process  which  yields  an  apparently  amorphous  lemon- 
yellow  powder.  Eecently  it  was  noticed  that  a  purchased  sample  of 
the  iodide  possessed  an  orange  tint,  together  with  the  peculiar  irides- 
cence of  the  crystalline  salt.  With  a  half-inch  power  it,  however, 
evinced  no  crystallescence.  But  this  indication  is  no  positive  evidence 
of  the  total  absence  of  crystals  since  various  amorphous  bodies  have 
the  capacity  of  utterly  concealing  crystalline  substances  mingled  with 
them.  Plumbic  acetate  does  not  form  a  clear  solution  when  dissolved 
in  water  alone.  Potassic  iodide  is  invariably  contaminated  with  car- 
bonate. Hence  these  two  causes  are  in  themselves  sufficient  to  over- 
come a  moderate  tendency  to  crystallescence  or  to  obliterate  such  crys- 
tals as  may  form.  In  order,  if  possible,  to  avoid  such  interference  a 
solution  of  plumbic  acetate,  rendered  limpid  with  a  little  acetic  acid, 
was  mixed  with  a  solution  of  ferric  iodide.  The  resulting  precipitate 
was  a  mixture  of  plumbic  iodide  and  free  iodine.  Plumbic  acetate 
was  then  treated  with  ferrous  iodide  in  a  similar  manner.    A  lemon- 
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