538  IODINE  FROM  THE  ASHES  OF  SEA-WEEDS. 
Same  strikes  the  front  of  the  pan,  and  dividing  there,  circle 
round  the  sides  and  escape  into  the  chimney  on  the  back.  This 
arrangement  allows  the  salts  deposited  to  collect  at  the  bottom, 
whence  they  are  easily  ladled  out. 
The  Extraction  of  the  Iodine. 
The  quantity  of  liquid  by  these  series  of  boilings  has  now  been 
reduced  to  one-sixteenth  of  its  original  bulk.  Or  to  make  it  still 
clearer,  allow  that  16  pansful  had  been  boiled  at  first,  and  now 
off  the  steeps  ;  these  by  evaporation,  and  parting  with  a  certain 
quantity  of  their  soluble  contents,  are  reduced  to  eight  pansful, 
which  again  make  four,  and  these  two,  until  at  the  fourth  boil  one 
pan  from  the  sixteen  remains  ;  this,  as  may  be  supposed,  is 
highly  concentrated,  and  holds  in  solution  the  iodine,  in  the 
form  of  an  iodide  or  iodate  of  soda  and  potassa.  After  this 
liquor  has  become  completely  cold,  it  is  ladled  into  an  iron  pan, 
(if  lined  with  lead  so  much  the  better,)  and  is  there  subjected  to 
the  action  of  sulphuric  acid  ;  unconcentrated  acid  is  best  for  this 
purpose  ;  and  to  a  quantity  of  liquor  remaining  after  the  process 
described  as  being  the  product  of  pans  of  the  size  indicated,  from 
8  to  10  carboys  of  acid  will  be  required  fully  to  saturate  the  free 
salts  contained.  The  acid  should  be  added  gradually,  as  by 
setting  two  carboys  over  the  neutralizing  pan,  and  allowing  it 
to  enter  the  liquid  by  means  of  small  leaden  syphons,  very  copi- 
ous evolutions  of  gas  are  liberated  during  this  process,  and  as 
the  mixture  must  be  diligently  stirred,  it  is  better  to  have  the 
operation  conducted  near  the  chimney,  into  which  a  hole  has 
been  made,  closed  when  not  in  use  by  a  damper ;  the  draft 
carries  off  the  noxious  vapors,  and  is  a  great  convenience  to  the 
workman.  The  acid  should  be  added  in  till  the  liquor  is  very 
sour,  and  a  few  drops  of  acid  added  to  a  small  quantity  evolves 
fumes  of  iodine  readily.  The  liquid  will  now  have  a  creamy 
yellow  appearance,  and  should  be  kept  undisturbed  (except  skim- 
ming the  sulphur  from  the  top,)  until  next  morning,  when  it  is  to 
be  transferred  to  the  stile  for  sublimation.  The  stile  should 
hold  the  above  mentioned  quantity  of  liquid  twice ;  its  size 
should  be  about  4  feet  in  diameter,  and  2J  feet  deep ;  the  bot- 
tom cast  to  two  inches  thick,  and  set  as  a  common  boiler  in  brick- 
work ;  a  leaden  dome  should  fit  into  a  flange  round  the  rim,  and 
