ON  LIQUOR  FERRI  IODIDI. 
171 
ON  LIQUOR  FERRI  IODIDI,  AND  THE  TESTS  OF  IODINE. 
By  Ferdinand  F.  Mayer,  of  New  York. 
In  laying  the  following  remarks  before  the  meeting,  I  must 
state  that  some  of  the  facts  I  shall  mention  are  truly  enough  not 
new ;  but  as  I  have  endeavored  to  arrange  and  harmonize  them 
with  my  personal  observations,  they  may  contribute  much  to  the 
understanding  of  the  changes  which  this  preparation  is  liable 
to,  and  of  the  remedies  proposed  for  their  alleviation. 
First,  as  to  the  strength  of  the  liquor.  I  have  made  this 
preparation  by  all  the  formulas  given  in  the  different  Pharma- 
copoeias and  books,  some  with  a  greater  or  less  excess  of  iron, 
some  with  iron  wire,  others  with  filings,  some  with  application 
of  heat,  others  without ;  some  filtered  into  sugar,  others  into 
syrup— but  in  not  a  single  instance  have  I  found  them  to  contain 
fully  the  proportion  of  iron  corresponding  to  the  amount  of  iodine 
employed. 
The  solution,  always  directed  to  be  made  by  digesting  iodine 
and  iron  in  varying  proportions,  is  of  an  acid  reaction.  It  is 
thus  not  only  shown  by  the  test  on  blue  litmus  paper,  which 
might  possibly  and  partly  be  supposed  to  arise  from  the  action 
of  the  iodide  on  the  organic  substance,  but  also  by  the  continued 
disengagement  of  hydrogen  gas,  if  ever  so  slow,  going  on  in  the 
solution  when  digested  at  a  higher  temperature  with  clean  iron 
wire  or  metallic  zinc.  That  a  formation  of  hydriodic  acid 
takes  place  during  the  reaction,  in  the  first  place,  of  iodine  on 
iron  is  made  quite  perceptible  by  the  smell  of  carburetted  hydro- 
gen arising  from  the  mixture,  especially  when  heated  or  made 
from  filings.  This  excess  of  hydriodic  acid  in  no  case  amounts 
to  more  than  two  per  cent,  of  that  in  combination,  but  is  in  no 
other  way  injurious  to  the  preparation.  A  deficiency  of  iron 
is  further  caused  by  the  never- wanting  impurities  of  iodine.  I 
shall  further  on  return  to  the  tests  of  this  substance. 
The  strength  of  the  officinal  solution  in  iodide  of  iron  should 
be  set  down  as  seven  grains  per  ounce. 
The  large  excess  of  iron  used  does  in  no  way  contribute  to 
increase  the  proportion  of  it  going  into  solution.  It  rather 
causes  a  loss  of  iodine  by  inducing  too  rapid  a  combination  and 
evolution  of  heat.  The  ingredients  should  be  kept  as  cool  as  pos- 
sible, though  it  may  require  a  little  more  time0    Application  of 
