342 
The  Stability  of  Iodine  Ointments. 
Fried9  prepared  iodine  ointment  according  to  the  U.  S.  P.  VIII 
formula,  and  assayed  it  at  intervals.  His  results  are  tabulated  here- 
with : 
Iodine  ointment  has  been  official  in  the  U.  S.  Pharmacopeia 
since  1870.  Briefly,  the  method  now  used  for  making  the  prep- 
aration is  as  follows : 
Four  Gm.  of  iodine,  4  Gm.  of  potassium  iodide  and  12  Gm.  of  glycerin 
are  weighed  into  a  tared  mortar  and  the  mixture  triturated  until  the  iodine 
and  potassium  iodide  are  dissolved  and  a  dark,  reddish-brown,  syrupy 
liquid  is  produced.  Eighty  Gm.  of  benzoinated  lard  are  then  added  in  small 
portions  and  with  trituration  after  each  addition.  The  mass  is  then  tritu- 
rated until  of  uniform  consistence.* 
*  The  time  required  to  complete  the  process  after  the  initial  portion  of 
lard  had  been  added  should  be  about  twenty  minutes. 
Iodine  ointment  is  officialized  also  in  several  foreign  pharma- 
copeias, although  the  iodine  strength  of  the  several  preparations  is 
not  uniform.  The  formula  in  the  British  Pharmacopeia  is  exactly 
like  that  in  the  U.  S.  Pharmacopeia  except  that  pure  lard  is  directed 
to  be  used  instead  of  benzoinated  lard.  Some  of  the  foreign  pharma- 
copeias also  specify  that  the  preparation  must  be  freshly  prepared 
when  wanted.  In  the  earlier  editions  the  U.  S.  Pharmacopeia  di- 
rected the  ointment  to  be  prepared  by  using  water  as  the  solvent  for 
the  potassium  iodide.  In  the  U.  S.  Pharmacopeia  VIII  the  formula 
was  changed  so  as  to  employ  glycerin,  and  that  solvent  is  now  official. 
Water  is  still  prescribed  as  the  potassium  iodide  solvent  by  the 
Pharmacopeias  of  the  Netherlands  and  of  France. 
From  the  examination  of  the  literature  it  seems  probable  that 
iodine  ointments  which  contain  petrolatum  products  only  as  the  oint- 
ment bases  are  apt  to  be  relatively  stable,  so  far  as  the  content  of 
free  iodine  is  concerned.    On  the  other  hand,  ointments  the  bases  of 
ter  cent 
Iodine  introduced  
Iodine  found  immediately  after  making 
Iodine  found  one  hour  after  making  . . 
Iodine  found  one  day  after  making  . . . 
Iodine  found  five  days  after  making  . . . 
Iodine  found  ten  days  after  making  . . . 
Iodine  found  thirty  days  after  making  . 
Iodine  found  ninety  days  after  making 
Iodine  found  eight  months  after  making 
3.89 
3.51 
348 
3-o6 
2.84 
2.81 
2.81 
2.81 
4.00 
9  P harm.  Jour.,  89,  610  (1912). 
