Am.  Jour.  Pharm.  \ 
November,  19 19.  J 
Iodine  Tinctures. 
731 
there  exist  significant  differences  in  this  respect  between  the  several 
iodine  preparations. 
Each  of  the  diluted  iodine  preparations  (2.2  per  cent,  iodine) 
was  diluted  with  10  volumes  of  water,  to  avoid  precipitation  of  pro- 
tein by  the  alcohol,  and  the  diluted  solution  added  to  an  equal  vol- 
ume of  a  10  per  cent,  solution  of  natural  egg-white  in  physiologic 
sodium  chloride  solution. 
The  simple  tincture,  that  with  hydrogen  iodide,  Burnham's  prep- 
aration, and  Surgodine,  produced  an  apparently  identical  coagulum. 
The  U.  S.  P.  tincture  (diluted  in  the  same  way)  produced  only  a 
turbidity;  this  also  when  the  quantity  of  the  iodine  solution  was 
doubled.  Next  morning,  the  albumin  was  coagulated  as  with  the 
others.    The  reaction  to  litmus  remained  neutral. 
The  restraining  action  of  the  potassium  iodide  is  limited,  for 
the  addition  of  an  equal  quantity  of  the  potassium  iodide  tincture 
to  the  hydriodic  acid  tincture  does  not  prevent  immediate  coagula- 
tion (1  volume  potassium  iodide  tincture,  1  volume  hydrogen  iodide 
tincture,  10  volumes  of  water). 
It  is  evident,  therefore,  that  the  potassium  iodide  of  the  official 
tincture  has  a  restraining  effect  on  the  coagulation  of  protein.  This 
would  tend  to  make  it  less  irritant  than  the  other  preparations.  It 
is  conceivable  that  this  may  be  disadvantageous  in  skin  protection, 
in  which  the  fixative  action  is  probably  desirable.  In  this  case,  how- 
ever, there  is  no  object  in  using  a  water-miscible  preparation,  and 
the  simple  alcoholic  solution  of  iodine  would  be  fully  as  good  as  any 
of  the  others. 
Capillarity  and  Spreading. — Dilute  tinctures  of  iodine,  when 
placed  on  the  skin  or  on  parchment,  tend  to  distribute  themselves  so 
that  the  solution  becomes  most  concentrated  at  the  periphery  (as  in 
the  accompanying  illustration).  In  this  manner,  the  periphery  of 
an  application  on  the  skin  may  be  blistered  when  the  center  is 
scarcely  affected.  If  this  property  were  more  marked  in  one  spec- 
imen than  another,  this  would  be  equivalent  to  greater  irritation. 
The  illustration  shows  that  this  uneven  distribution  runs  in  the 
order:  U.  S.  P.  (potassium  iodide  tincture),  most;  Burnham's  sol- 
uble iodine ;  hydrogen  iodide  tincture ;  Surgodine ;  alcoholic  tinc- 
ture (containing  no  potassium  iodide),  least. 
The  differences  are  in  favor  of  the  simple  alcoholic  tincture 
(which  was  formerly  official)  and  adverse  to  the  tincture  contain- 
ing potassium  iodide  (which  is  now  official)  ;  but  they  do  not  im- 
