42 
Churchill's  Tincture  of  Iodine.      (A™-  J°ur-  pharm- 
'  January,  19 19. 
delphia  College  of  Pharmacy  and  the  calculations  were  done  accord- 
ing to  the  method  of  Professor  Moerk.  The  references  to  percent, 
in  this  thesis  mean  the  customary  weight  in  volume  percentage. 
L   Iodine  in  Solution. 
The  following  are  the  results  of  the  various  experiments  with 
the  N.  F.  IV  tincture : 
A  tincture  assayed  directly  after  preparation  contained  only  10.88 
per  cent,  of  iodine  dissolved,  which  certainly  shows  the  need  of  more 
potassium  iodide. 
One  N.  F.  IV  tincture  was  allowed  to  stand  one  week,  another 
one  and  a  half  weeks  and  another  three  weeks  before  being  assayed 
for  the  percentage  of  iodine.  The  one  which  stood  one  week 
showed  only  12.13  per  cent,  of  iodine  in  solution  instead  of  the 
required  16.5  per  cent.  The  tincture  which  stood  one  and  a  half 
weeks  showed  14.97  per  cent,  of  iodine  with  only  a  few  granules 
remaining  visible  at  the  bottom  of  the  bottle.  The  preparation  which 
stood  for  three  weeks  before  being  assayed,  showed  that  only  15.6 
per  cent,  of  iodine  was  taken  up. 
Result. — 'My  experiments  proved  conclusively  that  there  is  not 
enough  potassium  iodide  in  the  tincture  to  completely  dissolve  the 
entire  amount  of  iodine. 
II.    Potassium  Iodide  Necessary. 
Experiments  were  then  conducted  by  making  new  tinctures  and 
adding  different  amounts  of  potassium  iodide. 
At  first  1  Gm.  of  potassium  iodide  was  added  to  100  mils,  making 
it  1  per  cent,  more  of  potassium  iodide,  a  total  of  4.3  per  cent. 
After  letting  the  tincture  stand  two  days  it  was  titrated  and  all  the 
iodine  was  found  to  be  dissolved. 
The  next  assays  were  made  with  a  tincture  having  one  half  Gm. 
of  potassium  iodide  added  to  each  100  mils  thus  containing  3.8  per 
cent.  A  titration  of  such  a  tincture  made  right  after  it  was  com- 
pleted showed  14.17  per  cent,  iodine  content.  A  few  such  tinctures 
were  set  aside  to  note  the  effect  of  time  upon  the  solubility  of  the 
iodine.  Such  a  tincture  containing  3.8  per  cent.  KI,  showed  14.41 
per  cent,  iodine  dissolved  on  standing  one  week.  On  standing  two 
weeks  it  showed  16.47  per  cent,  iodine  dissolved,  which  is  practically 
the  entire  amount. 
