308  ACTION  OF  IODINE,  BROMINE  AND  CHLORINE  UPON  SUGAR. 
To  explain  the  second  fact,  I  asked  myself  what  became  of  * 
the  free  iodine?  for  surely  it  could  not  combine  itself  with  the 
proto-iodide  of  iron  to  form  a  sesqui-iodide;  the  sesqui-iodide  of 
iron  being  red,  should  have  remained  so;  we  know,  upon  the 
other  hand,  that  water  dissolves  hardly  more  than  of 
iodine,  which,  after  some  chemists,  is  transformed  into  iodic 
and  hydriodic  acids.  The  last  question  was,  then,  to  know  how 
free  iodine  acted  upon  sugar. 
To  elucidate  this  question,  I  made  various  experiments  with 
iodine  and  simple  syrup.  I  soon  found  that,  with  a  moderate 
and  prolonged  heat,  this  metalloid  added  to  the  syrup  was  sub- 
ject to  a  great  chemical  change. 
One  to  ten  grains  of  iodine,  added  to  one  ounce  of  simple 
syrup,  in  a  strong  bottle  closed  with  a  glass  stopper,  the  whole 
exposed  in  a  water  bath  at  a  moderate  heat  (60°  Centigrade), 
are  dissolved  little  by  little,  and  give  the  liquid  a  reddish  brown 
color;  but  after  several  hours,  the  whole  being  always  kept  at 
the  same  temperature,  the  syrup  again  becomes  discolored.  The 
flask  must  be  cautiously  shaken  from  time  to  time.  The  whole 
operation  occupies  about  48  hours. 
In  operating  with  a  syrup  containing  |  drachm  of  iodine  to 
the  ounce,  I  obtained,  with  some  trouble,  however,  a  similar 
colorless  product. 
The  greater  the  proportion  of  iodine,  the  more  attention  is 
required;  and  towards  the  end  of  the  operation,  care  must  be 
taken  to  remove  the  syrup  as  soon  as  it  turns  white. 
Arrived  at  this  point,  if  the  preparation  is  left  exposed  to 
heat,  it  scon  colors  again  ;  by  and  by  the  sugar  is  transformed 
into  caramel ;  and  this  burned  sugar,  quickly  destroyed  in  its 
turn,  gives  rise  to  carbonic  acid  and  to  a  blackish,  light  and 
spongy  substance,  partly  soluble  in  water  and  alcohol.  Treated 
by  hydrochloric  acid,  potash,  &c.,this  substance  shows  the  same 
reactions  as  ulmin  and  ulmic  acid.  To  carry  on  this  operation 
to  the  entire  decomposition  of  the  sugar,  all  necessary  care 
must  be  taken  to  prevent  a  fracture  of  the  flask  by  the  expansion 
of  carbonic  acid  gas,  which  is  formed  in  quantities,  and  can  be 
collected. 
The  more  the  temperature  is  elevated,  the  larger  is  the  pro- 
portion of  iodine,  and  quicker  is  the  sugar  decomposed. 
