518  Action  of  Light  and  Heat  on  Sugars.  {^'^ocu't^%z!'^' 
tillation,  the  iodoform-producing  substance  was  detected.  In  another 
experiment  the  heating  was  prolonged  to  six  weeks;  the  solution 
became  much  daricer  in  color,  and  contained  some  yellowish-brown 
matter,  which  readily  dissolved  in  a  solution  of  potassium  hydrate^ 
from  which  it  was  again  precipitated  on  the  addition  of  an  acid.  The 
sokition  was  slightly  acid,  contained  2*8  per  cent,  of  glucose,  and 
yielded  the  iodoform-producing  compound.  It  would  appear,  then,, 
that  nothing  but  an  elevated  temperature  is  necessary  to  convert  an 
aqueous  sohition  of  cane-sugar  into  glucose  and  an  acid  body,  with  a 
minute  quantity  of  an  unknown  volatile  substance. 
Experiments  were  made  to  ascertain  whether  the  iodoform-yielding 
body  is  produced  immediately  from  glucose,  and  whether  carbonic 
anhydride  accompanies  its  formation.  400  cc.  of  a  5  per  cent,  solu- 
tion, prepared  carefully  by  ourselves,  were  boiled  in  a  retort,  and  the 
distillate  tested  from  time  to  time,  and  the  substance  we  were  in  search 
of  was  detected  in  successive  portions  of  the  distillate;  boiling  water 
was  added  to  the  residue  to  make  up  the  volume,  and  the  air  was 
driven  out  of  the  apparatus  by  a  stream  of  pure  hydrogen.  The  slow 
boiling  was  continued  for  12J  hours,  hydr(»gen  passing  through  the 
apparatus,  and  subsequently  through  tubes  containing  baryta- water ;: 
the  distillate  contained,  as  before,  a  small  quantity  of  the  volatile 
compound,  but  no  carbonic  anhydride.  It  is  evident,  therefore,  that 
the  chemical  reaction  is  essentially  different  from  a  vinous  fermenta- 
tion, and  that  the  iodoform-yielding  compound  is  not  alcohol  is  also 
proved  by  its  totally  distinct  odor,  and  the  different  volatility  of  its 
aqueous  solution ;  it  is  not  separated  from  water  by  potassium  car- 
bonate, and  no  other  means  have  been  found  for  its  isolation.* 
In  our  original  experiments,  in  which  the  copper-zinc  couple  was 
heated  to  about  100°  C.  with  cane-stigar  solutions,  only  traces  of 
glucose  were  ever  produced,  even  after  the  action  had  continued  for 
weeks.  This  agent  therefore  prevents  the  conversion,  probably  by 
neutralising  or  destroying  the  acid  compound  as  quickly  as  it  is  pro- 
duced. It  is  remarkable  also  that  a  solution  of  cane-sugar  remains 
colorless  apparently  any  length  of  time,  when  heated  with  the  copper- 
zinc  couple. 
^Mr.  Horace  T.  Brown  has  drawn  our  attention  to  a  paper  "On  the 
Electrolysis  of  Sugar  Solutions  "  in  Jour.  Chem.  Soc.  of  July,  1872.  He 
mentions  an  iodoform-producing  body,  which  was  probably  the  one  here- 
described,  as  he  subjected  his  solution  of  glucose  to  distillation. 
