Am.  Jour.  Pharni. 
Feb.,  1892. 
Volumetric  Solution  of  Iodine. 
IOI 
177  per  cent,  of  its  weight  of  iodine,  or,  to  put  it  differently,  the 
solubility  of  iodine  in  chloroform  is  1  in  56-6.  I  may  say  that  my 
results  with  a  solution  in  which  the  two  have  been  in  contact  for 
two  months,  are  practically  the  same  as  the  foregoing. 
While  working  at  the  subject  I  found  it  was  absolutely  necessary, 
to  get  good  results,  that  after  weighing,  the  chloroform  solution 
should  be  diluted  with  a  little  alcohol  before  adding  the  water,  as 
otherwise  the  iodine  would  be  thrown  out  I  found  it  also  neces- 
sary to  use  starch  as  an  indicator,  as  the  solution  became  apparently 
colorless  before  all  the  free  iodine  had  been  taken  up. — Phar.  Jour, 
and  Trans.,  January  2,  1892,  p.  544. 
NOTE  ON  VOLUMETRIC  SOLUTION  OF  IODINE. 
By  J.  H.  Hoseason. 
Read  before  the  Edinburgh  Assistant  Association;  reprinted  from  Phar.  Jour,  and 
Trans.,  January  16,  1892,  p.  583. 
Though  the  point  dealt  with  in  this  paper  might  seem  a  small 
one,  it  was  desirable  that  the  Pharmacopoeia  should  be  as  com- 
pletely accurate  in  every  detail  as  it  could  reasonably  be.  He  had 
prepared  a  standard  solution  of  iodine  with  which  he  had'  examined 
a  sample  of  arsenious  oxide,  and  found  it  to  be  pure.  Some  time 
after,  the  same  iodine  solution  was  used  with  the  same  sample  of 
arsenious  oxide,  and  it  indicated  only  97  per  cent.  As203.  It  was 
concluded  that  the  iodine  solution  had  deteriorated,  but  the  ques- 
tion came  to  be  how  could  its  strength  be  ascertained  without  using 
arsenious  oxide  as  a  factor.  Titration  with  standard  soda  solution 
was  tried,  but  the  end  reaction,  even  with  starch  paste,  was  not 
sufficiently  distinct.  Nitrate  of  silver  solution  was  also  found  to  be 
inapplicable,  as  a  portion  of  the  iodide  in  the  iodine  solution  com- 
bined with  the  silver  at  the  same  time.  Certain  points  noticed 
seemed  to  indicate  that  iodine  and  iodide  of  potassium  combined 
in  a  fixed  ratio,  but  time  did  not  permit  of  following  out  this 
inquiry. 
A  third  method,  which  proved  more  satisfactory,  was  to  add  a 
known  measure  of  standard  potassium  bichromate  solution  to  a 
solution  of  potassium  iodide  in  water  with  a  sufficiency  of  dilute 
sulphuric  acid.  Iodine  is  then  set  free  in  the  proportion  of  three 
molecules  to  one  of  potassium  bichromate.  Subsequent  titration  of 
this  iodine    with  sodium  hyposulphite  solution   determines  the 
