76 
Syrup  of  Ferrous  Iodide. 
f  A.m.  Jour.  Pharm. 
I  Febiuary,1903. 
how  can  we  conceive  of  the  formation  of  free  iodine  in  syrup  of  fer- 
rous iodide  without  the  simultaneous  production  of  a  ferric  com- 
pound ?  We  know  that  the  iodine  in  syrup  of  ferrous  iodide  is 
liberated  according  to  the  following  reaction : 
2FeI2  +  03  =  Fe2Os  +  2l2. 
Of  course,  there  may  be  some  intermediate  compounds  formed,  but 
this  no  doubt  is  the  final  reaction. 
Every  sample  of  discolored  syrup  of  ferrous  iodide  that  has  come 
under  the  observation  of  the  writer,  he  was  able  to  restore  to  its 
original  color.  Now,  it  the  discoloration  were  due  to  caramelization 
how  can  we  account  for  this  phenomenon  ?  The  writer  has  also 
found  ferric  compounds  present  in  every  sample  of  syrup  examinedt 
by  applying  potassium  sulphocyanate  T.S.  and  shaking  with  ether, 
when  the  characteristic  deep-red  color  was  taken  up  by  the  ethereal 
layer.  In  every  case,  the  potassium  sulphocyanate  T.S.  and  the  ether 
were  first  introduced  into  the  test-tube  and  shaken,  before  the  addi- 
tion of  the  syrup,  to  make  certain  that  no  trace  of  a  ferric  compound 
was  present  in  the  test-tube,  which  would  give  a  reaction  for  ferric 
iron  when  none  might  be  present  in  the  syrup. 
That  caramelization  takes  place  to  some  extent  occasionally,  is 
quite  possible;  but  that  it  is  the  cause  of  the  discoloration  of  syrup 
of  ferrous  iodide  in  most  cases  does  not  seem  probable. 
As  to  the  relative  merits  of  the  different  preservatives  suggested, 
we  should  note  that  thus  far  all  methods  and  means  suggested  as 
preservatives  of  syrup  of  ferrous  iodide,  with  the  single  exception 
of  hypophosphorous  acid,  while  they  have  proven  successful  in  the 
hands  of  some,  have  absolutely  failed  in  the  hands  of  others.  Hypo- 
phophorous  acid  seems  to  be  the  only  substance  to  hold  undisputed 
ground  as  an  effective  preservative  of  syrup  of  ferrous  iodide. 
As  to  the  presence  of  hypophosphorous  acid  in  syrup  of  ferrous 
iodide,  from  a  therapeutic  viewpoint,  the  writer  should  like  to  ask 
which  of  the  two  conditions  is  the  preferable  one :  To  have  a  syrup 
with  a  small  quantity  of  hypophosphorous  acid,  or  one  which  has 
been  discolored  and  contains  free  iodine,  with  the  accompanying  risk 
of  producing  iodism,  one  case  of  which  has  come  under  the  writer's 
observation. 
In  the  writer's  opinion  the  first  condition  is  surely  the  pref- 
erable one.    The  physiological  effect  of  free  iodine  we  need  not 
