﻿591 
  

  

  XLI. 
  — 
  On 
  Nitric 
  Acid 
  as 
  a 
  Source 
  of 
  the 
  Nitrogen 
  found 
  in 
  Plants. 
  

   By 
  George 
  Wilson, 
  M.D. 
  

  

  (Read 
  4th 
  April 
  1853.) 
  

  

  The 
  source 
  from 
  which 
  plants 
  obtain 
  nitrogen, 
  which 
  is 
  now 
  recognised 
  as 
  one 
  

   of 
  their 
  most 
  important 
  elements, 
  has, 
  from 
  the 
  first 
  recognition 
  of 
  its 
  importance, 
  

   been 
  matter 
  of 
  dispute. 
  Latterly, 
  however, 
  chemists 
  and 
  physiologists 
  have 
  

   pretty 
  unanimously 
  come 
  to 
  the 
  conclusion, 
  that 
  a 
  large 
  (perhaps 
  the 
  largest) 
  

   part 
  of 
  the 
  nitrogen 
  of 
  vegetables 
  is 
  derived 
  from 
  ammonia 
  ; 
  whilst 
  much 
  discus- 
  

   sion 
  has 
  been 
  carried 
  on 
  as 
  to 
  the 
  question, 
  Is 
  any 
  part 
  of 
  their 
  nitrogen 
  yielded 
  

   by 
  nitric 
  acid 
  ? 
  

  

  The 
  most 
  able 
  advocate 
  in 
  this 
  country 
  of 
  the 
  claims 
  of 
  ammonia 
  is 
  Dr 
  Gre- 
  

   gory. 
  The 
  most 
  able 
  advocate 
  of 
  the 
  claims 
  of 
  nitric 
  acid 
  is 
  Professor 
  Johnston 
  

   of 
  Durham, 
  and 
  the 
  opposite 
  conclusions 
  to 
  which 
  accomplished 
  chemists 
  like 
  

   these 
  have 
  come 
  in 
  reference 
  to 
  the 
  point 
  in 
  dispute, 
  have 
  perplexed 
  botanists, 
  who 
  

   know 
  not 
  which 
  view 
  to 
  prefer. 
  The 
  extent 
  to 
  which 
  they 
  are 
  pressed 
  by 
  this 
  

   dilemma, 
  has 
  been 
  so 
  strongly 
  represented 
  to 
  me 
  by 
  Dr 
  Balfour, 
  that 
  I 
  have 
  

   engaged 
  to 
  bring 
  the 
  subject, 
  as 
  I 
  now 
  do, 
  before 
  this 
  Society. 
  I 
  shall 
  sedulously 
  

   avoid 
  discussing 
  the 
  question 
  in 
  a 
  polemical 
  spirit 
  ; 
  and, 
  as 
  the 
  shortest 
  and 
  most 
  

   satisfactory 
  way 
  of 
  doing 
  justice 
  to 
  the 
  rival 
  views, 
  I 
  shall 
  select 
  Dr 
  Gregory's 
  

   clear 
  and 
  concise 
  statement, 
  as 
  representing 
  the 
  opinions 
  of 
  those 
  who 
  deny 
  that 
  

   nitric 
  acid 
  is 
  part 
  of 
  the 
  food 
  of 
  plants 
  ; 
  and 
  then 
  proceed 
  to 
  state 
  what 
  appear 
  to 
  

   me 
  conclusive 
  proofs 
  that 
  nitric 
  acid 
  does 
  supply 
  plants 
  with 
  nitrogen. 
  

  

  Dr 
  Gregory 
  writes 
  thus 
  : 
  — 
  " 
  Let 
  us 
  now 
  attend 
  to 
  the 
  nitrogen 
  of 
  plants. 
  

   This, 
  as 
  already 
  stated, 
  is 
  supplied 
  to 
  wild 
  plants 
  entirely 
  by 
  the 
  air, 
  and, 
  so 
  far 
  

   as 
  we 
  know, 
  only 
  in 
  the 
  form 
  of 
  ammonia. 
  Some 
  authors 
  have 
  held 
  that 
  nitric 
  

   acid 
  furnishes 
  nitrogen 
  to 
  plants, 
  and 
  that 
  this 
  acid 
  is 
  formed 
  in 
  the 
  air 
  by 
  

   thunder-storms, 
  and 
  carried 
  down 
  by 
  the 
  rain. 
  And 
  they 
  point 
  to 
  the 
  occur- 
  

   rence 
  of 
  nitric 
  acid 
  in 
  springs 
  in 
  proof 
  of 
  this. 
  Now 
  it 
  is 
  true 
  that 
  nitric 
  acid 
  

   is 
  formed 
  in 
  thunder-storms, 
  but 
  in 
  very 
  minute 
  quantity, 
  whereas 
  ammonia 
  is, 
  

   and 
  must 
  be, 
  present 
  in 
  the 
  air 
  at 
  all 
  times. 
  Indeed 
  there 
  is 
  reason 
  to 
  believe 
  

   that 
  the 
  nitric 
  acid 
  of 
  storms 
  is 
  produced 
  by 
  the 
  oxidation 
  of 
  the 
  ammonia 
  of 
  

   the 
  air, 
  as 
  in 
  nitrification, 
  where 
  ammonia 
  is 
  oxidised 
  into 
  nitric 
  acid 
  and 
  water 
  

   NH 
  3 
  + 
  8 
  =N0 
  5 
  , 
  3 
  HO; 
  so 
  that 
  even 
  if 
  nitric 
  acid 
  did 
  yield 
  nitrogen 
  to 
  plants, 
  

   that 
  nitrogen 
  would 
  be 
  derived 
  from 
  ammonia. 
  This 
  would 
  account, 
  too, 
  for 
  the 
  

   small 
  amount 
  of 
  nitric 
  acid 
  formed. 
  For 
  if 
  it 
  were 
  produced 
  by 
  the 
  action 
  of 
  elec- 
  

   tricity 
  on 
  the 
  nitrogen 
  and 
  oxygen 
  of 
  the 
  air, 
  there 
  seems 
  to 
  be 
  no 
  reason 
  why 
  it 
  

  

  VOL. 
  XX. 
  PART 
  IV. 
  7 
  X 
  

  

  