TINCTURA  lODINII  DECOLORATA. 
347 
the  first  few  hours  a  slight  decoloration  appeared  in  every  vial, 
but  was  most  decided  in  No.  9,  which  bleached  from  day  to  day, 
and  on  the  third  day  retained  only  a  deep  straw  color,  while  the 
others  had  lost  their  color  in  strict  proportion  to  the  quantity 
of  ammonia  present — No*  2  being  yet  very  dark,  though  con- 
siderably lighter  than  No.  1. 
For  complete  decoloration,  No.  9  required  5  days  ;  No.  8, 
8  days  ;  No.  7,  11  days ;  No.  6,  15  days  ;  No.  5,  21  days :  No. 
4,  27  days ;  No.  3,  37  days  ;  No.  2,  at  the  expiration  of  six 
weeks,  still  retained  considerable  color,  being  as  dark  as  No.  8 
on  the  second  day. 
From  the  above  data  the  following  working  formula  would 
appear  most  appropriate  for  general  application  : 
For  1  pint.  For  1^. 
Iodine,  oz.  38  grains. 
Alcohol,  13  f.  oz.         •  6if5 
Aqua  Ammon.  fort.  3  f.  oz.  11% 
Dissolve  the  iodine  completely  in  the  alcohol,  then  add  the 
ammonia.  This  occasions  at  first  a  dark  precipitate  of  iodide 
of  nitrogen,  which,  however,  soon  re-dissolves  and  is  entirely 
decomposed.  Set  aside  for  four  weeks  or  until  perfectly  color- 
less. Occasional  shaking  up  is  advantageous.  More  ammonia 
would  hasten  the  process  of  decoloration,  but  should  be  avoided. 
When  pure  materials  are  employed  no  filtration  is  necessary. 
If,  however,  the  presence  of  iodide  of  potassium  should  be 
deemed  preferable,  according  to  the  proportions  of  the  Tinctura 
lodinii  Composita,  U.  S.  P,  the  amount  of  ammonia  may  be  still 
farther  reduced,  as  over  half  of  the  whole  amount  of  iodine 
present  is  already  in  combination  with  potassium.  The  follow- 
ing experiment  was  made  to  ascertain  the  best  proportions — four 
vials  were  filled  with; 
No.  1.      No.  2.     No.  3.    No.  4. 
Iodine,  grains,  15  15         15  15 
Iodide  potassium,  gr.  30  30         30  30 
Alcohol,  fluid-drachms,  7J  7  6i  6 
Aqua  Amm.  fort,  fluid-drachms,       J  1  IJ  2 
No.  4,  lost  color  very  quickly,  and  on  the  fourth  day  was  only 
of  a  pale  straw  color ;  while  No.  1  was  yet  very  dark,  though 
