﻿PHOTOSYNTHESIS 
  BALY 
  239 
  

  

  was 
  to 
  be 
  found 
  in 
  some 
  unknown 
  impurity. 
  There 
  is, 
  however, 
  an 
  

   alternative 
  possibiHty, 
  and 
  one 
  which 
  is 
  more 
  in 
  keeping 
  with 
  the 
  

   known 
  facts 
  of 
  the 
  natural 
  photosynthesis 
  in 
  the 
  living 
  leaf. 
  There 
  

   is 
  no 
  doubt 
  that 
  in 
  this 
  reaction 
  the 
  carbonic 
  acid 
  is 
  converted 
  

   directly 
  into 
  carbohydrates 
  and 
  that 
  formaldehyde 
  as 
  such 
  is 
  not 
  

   produced, 
  and 
  it 
  seemed 
  that 
  the 
  most 
  probable 
  explanation 
  of 
  the 
  

   discrepancy 
  between 
  our 
  results 
  and 
  those 
  of 
  Porter 
  and 
  Ramsperger 
  

   was 
  that 
  the 
  action 
  of 
  the 
  ultra-violet 
  light 
  is 
  to 
  estabUsh 
  a 
  photo- 
  

   chemical 
  equilibrium. 
  

  

  GHoCOa^CeHiA+eOo, 
  

  

  which 
  reverts 
  to 
  carbonic 
  acid 
  again 
  in 
  the 
  dark. 
  In 
  the 
  presence 
  

   of 
  oxidizable 
  impurities 
  a 
  small 
  amount 
  of 
  carbohydrates 
  will 
  be 
  

   formed, 
  which 
  will 
  be 
  photochemically 
  decomposed 
  to 
  formaldehyde. 
  

   This 
  decomposition 
  of 
  all 
  the 
  carbohydrates 
  by 
  means 
  of 
  ultra-violet 
  

   light 
  is 
  well 
  known. 
  

  

  Theie 
  is 
  no 
  need 
  to 
  give 
  here 
  the 
  details 
  of 
  the 
  experiments 
  which 
  

   were 
  carried 
  out 
  to 
  test 
  this 
  view, 
  and 
  it 
  is 
  sufficient 
  to 
  say 
  that 
  con- 
  

   clusive 
  proof 
  was 
  obtained 
  of 
  the 
  reahty 
  of 
  the 
  equilibrium; 
  that 
  is 
  to 
  

   say, 
  carbohydrates 
  were 
  found 
  to 
  be 
  present 
  in 
  the 
  solution 
  during 
  

   irradiation 
  by 
  ultra-violet 
  light, 
  and 
  these 
  vanished 
  very 
  quickly 
  

   after 
  the 
  irradiation 
  was 
  stopped. 
  

  

  This 
  gave 
  us 
  at 
  once 
  a 
  starting 
  point, 
  because 
  it 
  seems 
  evident 
  

   that 
  if 
  a 
  harmless 
  inorganic 
  reducing 
  agent 
  were 
  added 
  to 
  the 
  solu- 
  

   tion, 
  carbohydrates 
  should 
  be 
  formed 
  in 
  quantity 
  on 
  exposure 
  to 
  

   the 
  ultra-violet 
  light. 
  Such 
  a 
  reducing 
  agent 
  is 
  ferrous 
  bicarbonate, 
  

   and 
  great 
  hopes 
  were 
  raised 
  when 
  it 
  was 
  found 
  that 
  a 
  saturated 
  

   solution 
  of 
  this 
  compound, 
  which 
  was 
  completely 
  colorless 
  when 
  

   prepared, 
  gave 
  a 
  copious 
  precipitate 
  of 
  ferric 
  oxide 
  on 
  exposure 
  to 
  

   ultra-violet 
  light. 
  It 
  was 
  evident 
  that 
  the 
  oxidation 
  took 
  place 
  by 
  

   reason 
  of 
  the 
  oxygen 
  in 
  the 
  carbohydrate 
  equilibrium 
  in 
  accordance 
  

   with 
  the 
  equation 
  

  

  4Fe(HC03)2 
  + 
  02 
  = 
  2Fe203 
  + 
  4H2O 
  + 
  8CO2 
  

  

  and 
  indeed 
  it 
  was 
  found 
  that 
  on 
  evaporation 
  of 
  the 
  exposed 
  solution 
  

   a 
  simple 
  sugar 
  was 
  obtained. 
  The 
  quantity 
  produced 
  was 
  very 
  

   disappointing 
  and 
  far 
  less 
  than 
  was 
  anticipated, 
  and 
  the 
  conclusion 
  

   was 
  forced 
  upon 
  us 
  that 
  some 
  unknown 
  factor 
  was 
  taking 
  part 
  in 
  the 
  

   process. 
  

  

  During 
  many 
  unsuccessful 
  endeavors 
  to 
  improve 
  the 
  yield 
  of 
  the 
  

   carbohydrates, 
  it 
  was 
  noticed 
  that 
  the 
  ferric 
  oxide 
  was 
  not 
  produced 
  

   in 
  the 
  body 
  of 
  the 
  solution, 
  but 
  only 
  on 
  the 
  walls 
  of 
  the 
  c{uartz 
  con- 
  

   taining 
  vessels 
  and 
  on 
  the 
  surface 
  of 
  the 
  iron 
  rods 
  used 
  to 
  make 
  the 
  

   bicarbonate. 
  This 
  led 
  us 
  to 
  suspect 
  that 
  the 
  surface 
  was 
  a 
  determin- 
  

   ing 
  factor, 
  and 
  we 
  at 
  once 
  changed 
  the 
  experimental 
  method 
  so 
  as 
  to 
  

  

  