ON  THE  REVISION  OF  THE  U.  S.  PHARMACOPOEIA.  53 
excess,  the  violence  of  the  first  reaction  is  controlled,  the  stir- 
ring avoided,  and  by  the  use  of  a  bottle  the  air  is  excluded,  and 
the  loss  of  iodine  diminished.  By  the  use  of  a  smaller  propor- 
tion of  water  the  filtration  and  evaporation  are  materially  short- 
ened and  smaller' vessels  are  required.  By  affecting  the  com- 
bination without  artificial  heat,  less  risk  is  involved,  while  the 
operation  is  equally  simple  and  easy,  and  more  convenient.  Af- 
ter the  first  active  reaction  subsides,  the  stopper  may  be  firmly 
fixed,  and  then  five  or  ten  minutes  shaking  produces  the  charac- 
teristic clear  green  color,  while  the  bottle  remains  entirely 
free  from  the  brown  stains  that  mark  the  commencement  of  de- 
composition. By  filtering  into  the  flask  in  the  manner  described, 
the  whole  solution  in  the  flask  and  filter  is  protected  during  the 
greater  part  of  the  time  by  an  atmosphere  of  steam,  and  the 
filter  is  washed  and  drained  in  the  same  atmosphere  by  the 
water  condensed  in  and  upon  it,  this  water  with  the  iodide  fall- 
ing back  into  the  flask.  The  long  iron  wire  stuck  into  the  flask 
after  the  funnel  is  removed  serves  mainly  to  render  the  boiling 
equable,  and  prevent  bumping. 
The  finished  preparation  is  in  bright,  dry,  metallic  looking 
masses,  somewhat  crystalline  in  fracture,  and  wholly  soluble  in 
water.  It  still  contains  a  little  water  that  might  be  driven  off 
by  more  protracted  and  more  gentle  heating  ;  but  as  the  remain- 
der of  the  process  would  involve  protracted  contact  of  air,  the 
resulting  decomposition  would  more  than  counterbalance  any 
advantage  sought  in  this  direction. 
As  sesquioxide  of  iron  forms  no  combination  with  iodine,  it 
might  be  supposed  that  rusty  wire  or  filings  would  be  as  good  as 
clean  iron,  and  for  some  time  the  writer  acted  upon  this  suppo- 
sition. Afterwards,  however,  he  became  convinced  that  clean 
iron  is  necessary  for  a  good  preparation. 
Since  it  has  been  pretty  conclusively  shown  that  the  presence 
of  metallic  iron  does  not  prevent  the  separation  of  sesquioxide, 
but  only  serves  to  recombine  the  iodine  of  the  original  compound, 
it  seems  desirable  rather  to  avoid  the  decomposition  that  occurs 
from  contact  of  the  air,  than  to  have  iron  present  during  the 
evaporation.  In  operating  on  a  larger  scale  the  writer,  there- 
fore, performs  the  filtration,  and  finishes  the  evaporation  in  an 
atmosphere  of  carbonic  acid,  and  is  thus  enabled  to  dry  the  pre- 
