October  11,  19(X). 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
331 
Carbonic  Acid  Gas  as  a  Fcrtiiiser. 
I  NOTICE  your  paragraph  about  nitrate  of  soda  in  the  Journal 
of  Horticulture  (page  272),  and  you  will  observe  that  1  have 
expressed  the  same  opinion  on  the  paper  which  I  enclose.  This 
paper,  is  a  copy  of  the  last  sheet  of  an  essay  I  have  written  describing 
a  process  which  I  have  perfected  for  effecting  the  synthesis  of  atmo¬ 
spheric  nitrogen  with  the  hydrogen  of  water  and  so  producing 
ammonia.  I  shall  read  that  paper  shortly  I  hope  before  one  of  the 
learned  societies,  but,  meanwhile,  if  you  wish  to  announce  the  fact  in 
your  columns,  pray  do  so.  Gaseous  ammonia  in  the  form  of  sulphate 
is  worth  about  £40  a  too ;  I  do  not  think  it  will  cost  more  than  30s. 
in  the  way  I  make  it. 
What  I  particularly  wish  to  ask  you  is  your  opinion  about  the 
value  of  carbonic  acid  gas  as  a  fertiliser.  You  will  observe  that  in 
my  paper  I  assert  it  nourishes 
plants.  That  is  m}^  opinion — 
of  course  I  may  be  wrong — 
based  upon  the  fact  that 
ammonic  carbonate  makes  plants 
grow  more  vigorously  than 
ammonia  per  se.  It  would  seem, 
therefore,  that  roots  absorb  or 
act  on  carbonic  acid  as  well  as 
leaves.  This  would  also  seem 
to  be  confirmed  by  the  fact  that 
soils  containing  much  decaying 
vegetable  matter  are  always 
fertile.  Of  course  the  oxidation 
of  organic  substances  develops 
heat,  which  would  assist  the 
plant,  but  I  cannot  help  think¬ 
ing  that  the  carbonic  acid  which 
is  produced  by  the  oxidation 
feeds  it  also.  We  know  what 
a  powerful  fertiliser  urea  is,  and 
that  substance  on  decomposing 
in  soils  generates  both  ammonia 
and  carbonic  acid.  You  will 
perceive  that  the  artificial  guano 
described  by  me  contains  mole¬ 
cular  quantities  of  urea  and 
ammonic  carbonate. 
I  find  that  ammonia  soon 
permeates  a  plant.  Is  it  not 
the  case  that  when  it  is  decom- 
pa-ed  by  the  plant  into  nitrogen 
and  hydrogen,  the  hydrogen 
that  is  liberated  helps  the  plant 
in  reducing  carbonic  acid  to 
carbon  ?  A  plant  reducing  car¬ 
bonic  acid  to  its  elements  in 
the  presence  of  ammonia  in 
accordance  with  the  equation 
4NH3  +  3COi  =  6H2O  +  4N  +  3C 
produces  72,000  heat  units.  If 
ammonia  is  absent  it  absorbs 
288,000  heat  units,  and  that 
amount  of  plant  force  is  wasted. 
It  seems  to  me  that  ammonia 
not  only  helps  a  plant  to  do 
its  work  of  splitting  up  carbonic  acid,  but  at  the  same  time  supplies 
it  with  water  to  work  with  and  the  nitrogen  it  requires  for  its 
tissues. 
It  is  quite  unnecessary  for  me  to  make  any  remarks  about  the 
importance  of  cheap  ammonia  to  the  manufactures  of  this  and  other 
countries  ;  its  uses  in  the  arts  are  many.  I  will,  however,  take  this 
opportunity  of  pointing  out  a  matter  of  some  moment  to  humanity  at 
large.  Nitrogen  in  the  form  of  ammonia  is  the  most  powerful  plant 
fertiliser  known ;  it  is  very  valuable  when  combined  with  soda. 
Nitrate  of  soda,  containing  some  16  per  cent,  of  nitrogen,  is  used  in 
agriculture  to  the  amount  of  million  tons  annually.  Large 
quantities  of  sulphate  of  ammonia,  in  which  is  about  25  per  cent,  of 
the  alkaline  gas,  are  similarly  employed.  In  both  these  cases, 
however,  there  is  a  great  prop)ortion  of  substances  combined  with  the 
nitrogen  and  ammonia  which  have  no  value  as  fertilisers,  and  hence 
there  is  much  waste. 
Now  it  is  quite  easy  to  prepare  from  ammonia  a  fertiliser  which  is 
all  plant  nourishment,  containing  no  waste  material  whatever.  It  is 
only  necessary  to  bring  ammonia  in  contact  with  carbonic  acid  gas, 
which  is  produced  abundantly  wherever  fires  are  burning,  to  obtain  a 
white  S)li'l,  ammonic  cirbonate,  by  the  union  of  thosp  gases.  We 
may  go  a  step  further  and  produce  artificial  guano — artificial  indeed, 
blit  much  more  valuable  from  its  great  purity  than  the  natural  article. 
When  ammonic  carbonate  is  heated  to  about  140  C.  in  a  closed  vessel 
it  undergoes  a  change,  and  is  converted  into  a  mixture  of  urea  and 
ammonic  carbonate.  Whoever  desires  to  make  half  a  dozen  ears  of 
corn  grow  where  one  is  produced  now  may  realise  his  wishes  by  using 
a  little  of  that  mixture. — W.  Mills. 
[From  a  new  book*  that  has  just  reached  us,  an  i  which  is  likely 
to  be  of  great  value  to  students  in  agri-horticultural  schools  an  ! 
colleges,  we  extract  the  follow  ing  obs'  rvations  bearing  on  the  value 
of  carbonic  acid  gas  (carbon  dioxide)  and  its  appropriation,  about 
which  our  correspondent  inquires : — 
The  source  from  which  plants  obtain  the  large  quantity  of  carbon, 
of  which  more  than  half  their  dry  weight  consists,  has  been  the 
source  of  extensive  investigation  for  a  long  time. 
Parasitic  plants,  such  as 
dodder,  broom  rape,  and  many 
fungi,  attach  themselves  to  other 
living  organisms  and  absorb  the 
carbon  they  need  in  the  form 
of  sugar,  proteids,  and  other 
elaborated  carbon  compounds 
from  their  victims.  Sapro¬ 
phytes,  such  as  the  bird’s-nest 
orchis  (Neottia),  mushrooms,  and 
the  majority  of  common  fungi, 
which,  like  the  above  mentioned 
parasites  are  devoid  of  chloro- 
plasts,  obtain  their  carbon  in  a 
similar  elaborated  form  from  the 
carbon  compounds  present  iu 
the  remains  of  dead  plants  and 
animals  on  which  they  grow. 
It  is  probable  also  that  all 
green  plants  absorb  and  utilise 
organic  carbon  compounds  from 
the  humust  or  decaying  vege¬ 
table  and  animal  remains  within 
the  soil,  although  it  has  been 
proved  that  this  source  is  in¬ 
sufficient  to  supply  all  the  carbon 
needed  for  the  perfect  healthy 
nutrition  of  plants  of  this  kind. 
By  the  method  of  water  cul¬ 
ture  or  sand  culture  it  may  be 
readily  shown  that  ordinary 
green  plants  flourish  and  increase 
in  carbon-content  when  their 
roots  are  supplied  with  a  solution 
of  food  materials  containing  no 
carbon,  so  long  as  the  solution 
contains  all  other  essential 
elements.  Under  these  circum¬ 
stances  the  only  source  of  carbon 
is  the  carbon  dioxide  of  the  atmo¬ 
sphere  surrounding  the  leaves. 
In  the  processes  of  fermen¬ 
tation  and  decay  going  on  in 
ordinary  soil  carbonic  dioxide  is 
produced,  and  the  air  permeating 
the  interstices  of  the  soil  may 
contain  as  much  as  5  per  cent, 
of  this  gas,  some  of  which  enters 
the  roots  of  plants  dissolved  in 
the  water  of  the  transpiration- 
current’;  it  has,  however,  been  shown  by  Cailletetand  Moll  s  experiments 
that  the  supply  of  carbon  dioxide  obtained  in  this  manner  is  insufficient 
for  the  requirements  of  ordinary  green  plants. 
Extended  and  carefully  conducted  experiments  have  proved  beyond 
doubt  that  the  chief  food  material  utilised  by  green  plants  for  their 
carbon  supply  is  the  carbon  dioxide  of  the  air,  and  that  this  gas  is 
absorbed  by  the  leaves.  Moreover,  it  is  through  the  stomata  that  the 
gas  enters  into  the  tissues,  and  only  in  slight  degree,  if  at  all,  through 
the  cuticle  of  the  epidermal  cells. 
Mr.  Percival  is  Professor  of  Botany  in  the  South-Eastern  Agri¬ 
cultural  College,  Wye,  and  is  known  as  a  diligent  investigator.  His 
work  is  up  to  date,  and  has  been  accepted  as  a  text  book  at  the 
Cambridge  University;  therefore,  a  better  “opinion”  than  his  can 
scarcely  be  had  on  the  subject  on  which  Mr.  Mills  particularly  desires 
information.  The  other  portion  of  his  communication  is  left  for  the 
consideration  of  Mr.  Abbey  and  other  scientific  readers,  who  may  be 
interested  in  the  propositions  advanced.] 
*  “Agricultural  Botany,”  by  John  Percival,  M..4..  F.L.S.  (Duckworth 
and  Co.,  Henrietta  Street,  Oovent  Garden.) 
Fio.  92. —Tomato  Fairfield. 
