A.m.  Jour.  Pharm.  \ 
January,  1901.  J 
Syrup  of  Iodide  of  Iron. 
contradictory  suggestions,  such  as  exposure  to  direct  sunlight  on 
one  hand  and  entire  exclusion  of  light  on  the  other,  gradually 
turns  darker. 
The  fact  that  application  of  the  starch  test  gave  negative  evi- 
dence of  the  presence  of  free  iodine  indicated  the  necessity  of 
another  explanation. 
This  was  believed  to  be  found  by  advancing  the  theory  that  a 
ferric  compound  is  formed,  and  the  statement  that  ferrous  iodide 
changed  to  ferric  iodide  or  oxyiodide  was  accepted  as  conclusive. 
This  change  probably  takes  place  if  an  aqueous  solution  of 
ferrous  iodide  is  evaporated  with  the  view  of  obtaining  the  salt, 
but,  based  upon  results  obtained  from  the  examination  of  a  number 
of  specimens  of  various  age  and  shade  of  color,  the  writer  ques- 
tions if  this  takes  place  in  the  syrup. 
In  an  examination  of  some  fifteen  discolored  samples  not  one 
reacted  for  the  presence  of  ferric  compounds. 
This  result  practically  excludes  this  theory,  and  the  cause  of  dis- 
coloration must  be  sought  elsewhere. 
Recently  the  action  of  free  acids  upon  syrups  has  received  atten- 
tion, and  the  changes  produced  thereby  have  been  described.  Con- 
siderable work  still  remains  to  be  done  in  this  direction,  and  the 
action  of  metallic  salts,  in  particular  those  of  an  acid  reaction,  upon 
saccharine  solutions  demands  exhaustive  investigation* 
Regarding  the  reaction  of  ferrous  iodide,  the  statements  of  the 
Pharmacopoeia  are  contradictory,  the  saccharated  iodide  being 
stated  to  have  a  slightly  acid  and  the  syrup  a  neutral  reaction. 
Founded  on  the  results  of  an  investigation  carried  on  for  some  time, 
the  writer  inclines  to  the  belief  that  the  action  of  the  iron  salt,  with- 
out itself  undergoing  any  chemical  change,  causes  discoloration  of 
the  syrup. 
The  amount  of  heat  employed  in  preparing  the  syrup  also  has  an 
important  influence. 
The  following  reasons  may  serve  to  substantiate  these  assertions : 
Ferrous  iodide  is  not  the  only  iron  salt  which,  with  the  influence 
of  heat,  causes  darkening  in  syrup. 
A  syrup  of  ferrous  sulphate,  containing  10  per  cent,  of  the  salt, 
prepared  by  dissolving  sugar  in  an  aqueous  solution  and  heating  to 
boiling,  on  standing  from  4  to  6  months  with  exposure  to  light, 
turned  from  a  light  green  to  a  brown  color. 
Examination  at  the  expiration  of  six  months,  with  the  view  of 
