ON  LIQUOR  FERRI  XODIDI. 
175 
on  this  reaction.  Any  one  may  repeat  the  experiment  with  a 
dark  liquor  ferri  and  a  small  quantity  of  iodine,  tincture  of 
iodine,  or  iodide  of  potassium.  The  result  will  in  all  cases  be 
a  protosalt  of  iron.  Acting  on  this  principle,  the  evaporation 
of  the  solution  in  water  will  be  rendered  more  simple,  and  will 
furnish  a  perfectly  soluble  salt,  if,  during  evaporation,  a  small 
excess  of  iodine  be  directed  to  be  added. 
But  even  though  the  Liquor  Ferri  Iodidi  when  heated  with 
iodine  may  have  lost  none  of  its  original  qualities,  its  perma- 
nency is  hardly  better  than  before.  Nor  does  the  presence  of 
bright  iron  wire  in  the  syrup  appear  to  prevent  the  separation 
of  sesqui-oxide.  Among  the  deoxidizing  substances  within  our 
reach,  there  is,  however,  one,  the  chemical  and  medicinal  pro- 
perties of  which  are  by  this  time  well  understood,  which  in 
analysis  is  frequently  employed  to  act  either  on  iodine  or  sesqui- 
oxide  of  iron,  and  which,  besides,  is  very  cheap, — I  mean  the 
Hyposulphite  of  Soda.  You  will  find  among  the  preparations 
submitted  to  the  inspection  of  the  meeting  a  bottle  labelled 
"  Protoiodide  of  Iron,  without  Sugar."  It  is,  or  ought  to  be, 
a  perfectly  limpid,  pale  green  liquid,  containing  the  same  pro- 
portion of  iron  as  the  officinal  liquor,  but  one-sixteenth  more 
than  the  amount  of  iodine.    It  is  prepared  as  follows  :  — 
Take  of  Iodine,      .       .       .    two  ounces  and  one  drachm. 
Fine  Iron  Wire,         .    six  drachms. 
Pure  Water,      .       .    q.  s. 
Hyposulphite  of  Soda,   two  drachms. 
Place  two  ounces  of  the  iodine  with  five  ounces  of  water  in  a 
glass  flask  or  prescription  bottle,  add  the  iron  gradually,  and 
shake,  unless  the  mixture  becomes  too  warm,  until  a  pale  green 
solution  is  obtained.  This  pour  off  into  a  tincture-bottle  marked 
at  the  point  indicating  twenty  fluid  ounces.  Add  the  last 
drachm  and  agitate  until  dissolved.  Rinse  out  the  first  flask 
with  some  water,  which  is  added  to  the  iodine  solution.  Then 
dissolve  the  hyposulphite  of  soda  in  enough  cold  water,  and  add 
it  gradually  to  the  solution  of  iron  until  the  latter,  under 
shaking,  is  discolored.  Dilute  to  twenty  ounces,  and  filter  in  a 
glass-stopper  bottle.  If  two  drachms  of  hyposulphite  are  insuf- 
ficient to  discolor,  it  is  a  proof  of  its  impurity,  and  more  should 
be  added  until  the  result  is  attained.  If  too  much  has  been  added, 
