im"^""" }      Action  of  Light  and  Heat  on  Sugars.  519 
2.  Influence  of  Light,  Atmospheric  Germs,  and  Air. 
It  seemed  of  interest  to  examine  some  of  the  conflicting  statements 
in  regard  to  the  conversion  of  cane-sugar  into  glucose.  A  number  of 
the  tubes  previously  described  were  very  nearly  filled  with  a  5  per  cent, 
solution.  Twelve  were  sealed,  while  the  solution  was  boiling,  and  six 
of  them  were  exposed  to  full  daylight  at  ordinary  temperatures,  the 
other  six  being  kept  in  the  dark.  Six  more  were  opened  to  the  air, 
the  tubules  being  plugged  with  cotton-wool,  and  three  of  them  were 
exposed  to  daylight,  and  sometimes  to  the  direct  rays  of  the  sun,  the 
other  three  being  kept  in  complete  darkness.  Six  others  were  pre- 
pared with  the  tubules  open,  three  being  exposed  to  the  light,  and 
three  kept  in  the  dark.  After  allowing  the  whole  of  these  tubes  to 
remain  from  December,  1877,  to  May,  1879,  the  solutions  were  ex- 
amined for  glucose  and  fungoid  growths.  The  amounts  of  glucose 
found  in  the  several  experiments,  are  shown  in  the  subjoined  table : — 
Nature  of  Experiment. 
Solution  boiled  in  tubes,  but  not 
exposed  to  liglit,  etc  
Jn  sealed  tubes. 
(i)  .  Exposed  to  light  
(ii)  .  In  darkness  
In  txihes  plugged  with  cotton-wool. 
(i)  .  Exposed  to  light  
(ii)  .  In  darkness  
In  open  tubes. 
(i)  .  Exposed  to  light  
(ii)  .  In  darkness  
Grams  of  Glucose  in  100  c.  c. 
0-0162 
0-0187 
0  -0145 
0 -0203 
0-0246 
0  '0366 
0  -0214 
II. 
0-0185 
0-0116 
0  -0250 
0  -0193 
0-0272 
0-0225 
0-0325 
III. 
0  -0162 
0-0193 
0  -0152 
0-0261 
0-0262 
0  -0490 
0-0354 
IV. 
0 -0168 
0 -0160 
0-0232 
V. 
0-0219 
0  -0145 
0-0203 
VI. 
0-026 
As  the  very  method  of  preparing  these  solutions  produces  about  as 
much  glucose  as  was  found  in  the  tubes  17  months  afterwards,  the 
above  results  show  that  neither  light  nor  air,  singly  or  jointly,  changes 
cane-sugar  in  aqueous  solution  at  the  ordinary  temperature. 
As  Rouet  (Compt.  rend,  for  1871,  p.  1040)  states  that  a  solution  of 
10  grams  of  white  cane-sugar  in  50  grams  of  water,  enclosed  in  sealed 
tubes  from  which  the  air  has  been  expelled  by  boiling  the  liquid,  and 
exposed  for  five  months  to  light,  was  found  to  be  half-converted  into 
