^'"'ocriss?'^'"'}      Action  of  Light  and  Heat  on  Sugars.  517 
ON  THE  ACTION  OF  LIGHT  AND  HEAT  ON  CANE 
AND  INVERT  SUGARS. 
By  J.  H.  Gladstone,  Ph.D.,  F.E.S.,  and  Alfred  Tribe,  F.C.S., 
Lecturer  on  Chemistry  in  Dulwich  College. 
Nothing  is  more  familiar  to  chemists  than  that  living  yeast-cells, 
and  some  other  vegetable  structures^  are  capable  of  resolving  cane- 
sugar  into  alcohol  and  carbonic  anhydride;  and  this  decomposition  is 
the  more  interesting  as  all  attempts  to  bring  it  about  by  known 
•chemical  or  physical  processes  have  hitherto  failed.  We  thought  it 
worth  while  to  try  the  effect  of  the  copper-zinc  couple  at  the  ordinary 
temperature.  The  reaction  did  not  take  place  in  a  5  per  cent,  solution 
of  cane-sugar  :  hydrogen  was  of  course  evolved  (from  the  water),  but 
no  carbonic  anhydride.  At  100°  C,  however,  carbonic  anhydride  was 
slowly  evolved,  and  a  small  quantity  of  liquid  distilled  over,  which 
gave  iodoform  on  treatment  with  iodine  and  potassium  hydrate,  and 
acetic  acid  on  treatment  with  potassium  chromate  and  sulphuric  acid. 
Our  hopes  appeared  to  be  realized,  but  on  examining  the  chemical 
change  more  fully,  we  found  that  the  carbonic  anhydride  did  not  come 
from  the  sugar  at  all,  and  that  the  organic  substance  which  distilled 
over  was  not  alcohol,  and  was  not  dependent  upon  the  couple  for  its 
formation.  In  fact,  the  carbonic  anhydride  arose  from  the  splitting 
up  of  oxicarbonate  of  zinc,  which  is  formed  in  the  washing  of  the 
couple,  and  of  which  we  had  no  previous  knowledge;  while  the  organic 
body  is  a  product  of  the  action  of  heat  upon  the  sugar  solution. 
While  investigating  this  subject,  we  made  various  observations 
regarding  the  influence  of  heat,  light,  germs,  and  air  upon  solutions  of 
cane  and  altered  sugar  (glucose),  and  as  they  may  help  to  clear  up 
«ome  of  the  contradictory  statements  that  have  been  made  upon  this 
subject,  we  are  induced  to  record  the  most  important  of  them. 
1.  The  Action  of  Heat  on  an  Aqueous  Solution  of  Cane-Sugar. 
The  usual  mode  of  experimenting  was  to  take  a  number  of  tubes 
with  narrow  tubules  of  about  20  cc.  capacity,  and  nearly  fill  them 
with  a  solution  of  pure  cane-sngar  (5  grams  to  100  cc.  of  distilled 
water),  which  was  then  boiled  for  about  five  minutes  in  an  oil-bath. 
To  determine  the  effect  of  heat  in  absence  of  air,  some  of  the  tubes 
were  sealed  while  the  liquid  was  still  boiling.  About  15  cc.  of  the 
solution  in  a  sealed  tube  were  exposed  for  14  days  to  a  temperature  of 
90°  to  95°  C;  it  slowly  became  of  a  pale  yellow  color,  and  was  found 
to  contain  3*6  per  cent,  of  glucose,  was  acid  to  test-paper,  and,  on  dis- 
