Am.  Jour.  Pbarm. 
July,  1895. 
Syrup  of  Ferrous  Iodide. 
363 
With  the  idea  of  ascertaining  the  condition  of  the  article  as  sup- 
plied to  the  retail  trade, by  manufacturing  firms,  ten  samples  were 
procured  and  examined  in  regard  to  both  free  iodine  and  amount  of 
ferrous  iodide  contained. 
Some  of  the  samples  were  obtained  directly  from  the  producers ; 
the  others  were  bought  from  retail  pharmacists. 
That  a  comparison  of  the  results  might  be  made  with  those 
obtained  from  a  product  of  the  official  process,  the  author  prepared 
a  sample  by  this  means.  It  possessed  the  standard  pale  green 
color. 
The  test  with  starch  was  employed  to  detect  the  presence  of  free 
iodine.  The  content  of  ferrous  iodide  in  the  samples  was  deter- 
mined by  the  official  method,  which  consists  of  completely  precipi 
tating  the  iodide,  in  the  presence  of  nitric  acid,  by  the  addition  in 
excess  of  a  known  volume  of  decinormal  silver  nitrate  volumetric 
solution,  and  of  subsequent  titration  of  the  excess  of  silver  in  the 
known  volume  with  a  decinormal  potassium  sulphocyanate  volu- 
metric solution. 
The  estimation  is  ordered  to  be  performed  in  the  presence  of 
ferric  ammonium  sulphate,  which  will  indicate,  by  the  production 
of  a  red  color  of  ferric  sulphocyanate,  upon  the  continued  addition 
of  the  potassium  sulphocyanate  solution,  the  complete  precipitation 
of  the  excess  of  silver. 
In  adjusting  the  strength  of  the  potassium  sulphocyanate  solu- 
tion, by  titration  against  decinormal  silver  nitrate  volumetric  solu- 
tion, the  Pharmacopoeia  directs  -5  c.c.  of  ferric  ammonium  sulphate 
test  solution  to  be  used  as  the  indicator,  whereas,  in  the  estimation 
of  ferrous  iodide  in  the  official  syrup,  it  orders  5  c.c.  of  the  same 
test  solution. 
Tentative  experiments  having  shown  that  the  results  obtained 
when  the  smaller  volume  was  used  were  as  uniform  as  those  afforded 
in  the  presence  of  the  larger  volume,  the  smaller  amount  was 
adopted,  for  the  reason  that  the  solution  of  potassium  sulphocya- 
nate was  standardized  by  its  aid. 
The  following  results  show  about  one-half  of  the  syrups  of 
ferrous  iodide  placed  on  the  market  by  manufacturing  pharmacists 
to  be  of  good  quality. 
The  percentage  results  were  calculated  from  the  amount  of  deci- 
normal potassium   sulphocyanate  volumetric   solution  over  1  c.c. 
