Am.  Jour.  Pharni. 
July,  1887. 
Ammonium  Iodide. 
339 
more  concentrated  solution  than  usual,  whilst  the  washing  out  of  the 
salt  is  effected  with  relatively  little  water.  These  conditions,  hence, 
necessitate  the  expulsion  of  comparatively  less  water,  and  conse- 
quently occasion  the  exposure  of  the  salt  during  a  more  limited  period. 
In  connection  with  this  also  goes  the  important  advantage  derived 
from  the  ready  manner  of  producing  the  required  calcium  iodide. 
Elsewhere  (Amer.  Jotir.  Pharm.,  May,  1883)  the  writer  gave  a  pro- 
cess for  this  purpose.  This  permits  the  generation  of  the  ferric  iodide, 
calcium  iodide,  and  finally  ammonium  iodide,  in  an  uninterrupted 
course  requiring  no  large  variety  of  utensils  and  but  a  single  filtra- 
tion. Ultimately  the  'ammonium  salt  is  absolutely  free  from  iron 
and  calcium.  A  fine  annealed  iron  wire  should  be  used  in  abundant 
excess  in  the  preliminary  production  of  ferrous  iodide.  This  form  of 
iron  contains  some  carbon  and  traces  of  other  substances  which  either 
remain  or  become  insoluble  during  the  operation.  An  only  seemingly 
considerable  grayish  flocculent  residue  separates ;  this,  however,  is  but 
the  superficial  magnetic  oxide  of  iron  with  which  the  wire  becomes 
covered  during  its  manufacture.  In  order  to  avoid  any  possible 
excess  of  iodine  in  the  generation  of  the  ferric  iodide,  more  than  two- 
thirds  of  the  iodine  is  employed  in  the  formation  of  the  ferrous  salt. 
In  this  case  the  precipitated  ferric  hydrocarbonate  is  as  compact  and 
granular  as  usual.  These  various  considerations  have  led  to  the  con- 
struction of  the  following  formula  : 
Iron  wire,  very  fine  and  in  long  spiral  loops  1  troy  ounce. 
Iodine  3   "  ounces. 
Calcium  carbonate  precipitated  "  " 
Ammonium  bicarbonate  cryst  If  "  " 
Ammonia  water, 
Sulphurous  acid, 
Water,  of  each  sufficient. 
Mix  two  and  one-eighth  troy  ounces  of  the  iodine  with  the  iron 
wire  and  eight  fluid  ounces  of  water  and  set  the  mixture  aside,  stirring 
it  up  occasionally  until  complete  combination  has  been  effected.  De- 
cant the  light  green  liquid,  wash  the  residuary  iron  .  wire  with  two 
fluid  ounces  of  water  and  unite  the  washings  with  the  first  decantate. 
To  this  mixture  now  add  the  remaining  iodine  and  when  it  has  wholly 
dissolved,  gradually  add  the  calcium  carbonate,  facilitating  its  decom- 
position towards  the  last  by  the  application  of  a  gentle  heat.  Then 
gradually  add  the  ammonium  bicarbonate,  heat  the  mixture  until  ef- 
fervescence has  nearly  ceased  and  filter  it  when  nearly  cooled.  Wash 
