548  Permanent  Syrup  of  Ferrous  Iodide.  {^'^Nov!;m^'"^' 
ducing  in  its  action,  and,  in  proper  quantities,  capable  of  preserving 
the  syrup  intact,  without  precipitation  or  decomposition. 
A  sample  of  the  syrup  made  last  J uly  and  kept  in  an  ordinary  five 
pint  stock  bottle,  is  here  shown.  You  will  observe  that  it  is  a  clear, 
transparent,  greenish  liquid,  odorless,  having  a  sweet,  strongly  ferru- 
ginous taste.  It  is  neutral,  but  it  should  be  mentioned,  however,  that 
litmus  paper  is  no  test  of  its  neutrality  since  glucose  in  solution,  espe- 
cially syrupy  glucose,  will  redden  litmus.  With  potassium  sulpho- 
cyanide  the  presence  of  a  ferric  salt  is  contra-indicated.  It  has  kept 
during  that  time,  although  freely  exposed  to  air,  without  the  slightest 
change  in  color. 
Relative  to  the  present  pharmacopoeial  process,  it  is,  in  essentials,  the 
same  as  that  of  1870,  but  in  it  there  seems  to  have  been  ordered  a 
change  of  procedure  without  any  sufficiently  compensating  advantages, 
when  it  was  directed  to  filter  the  aqueous  solution  of  ferrous  iodide 
into  the  sugar,  heat  to  the  boiling  point  and  dissolve,  instead  of  follow- 
ing the  older  and  simpler  plan,  of  mixing  the  filtrate  direct  with  syrup. 
If  the  U.  S.  P.  1880  syrup  had  been  made  so  as  to  contain  full  65  per 
cent,  of  sugar,  as  in  simple  syrup,  instead  of  60  per  cent,  then  the 
chauge  might  have  been  consistently  ordered  on  the  score  of  preserva- 
tion, but  as  long  as  this  was  not  done,  it  practically  made  little  differ- 
ence between  the  two  formulas. 
The  formula  is  as  follows : 
Iodine,  875  grains. 
Iron  wire(Card  Teeth),  300  grains. 
Water,   3  fluidounces. 
Glucose  (solid),   2  troy  ounces. 
Syrup,  a  sufficient  quantity,  to  make  one  pint. 
Mix  the  iodine,  iron  and  water  in  a  flask,  shake  occasionally  until 
the  reaction  has  ceased  and  the  liquid  has  lost  its  iodine  odor.  Then 
heat  to  212°  F.  (100°  C),  filter  into  a  capsule  containing 
the  glucose,  finely  cut  up,  dissolve  at  a  low  heat  upon  a  water  bath, 
and  add  sufficient  syrup  to  make  the  desired  quantity. 
The  watery  solution  of  ferrous  iodide  is  directed  to  be  heated,  after 
the  reaction  has  taken  place  in  the  cold,  in  order  to  have  thorough 
chemical  combination.  Very  often  this  cold  solution,  although  the 
liquid  has  lost  its  iodine  odor,  is  of  a  yellowish  color,  which,  however, 
on  the  application  of  heat,  becomes  the  normal  green  tint;  showing 
that  heat,  at  the  latter  part  of  the  process  at  least,  is  essential.  A 
