329 
On  the  rower  of  Soils  to  absorb  Manure. 
some  eases  in  a free  state — that  is  to  say,  uncombined  with 
silica  or  any  other  acid.  Further,  alumina  has  a tendency  to 
play  the  part  of  a weak  acid,  and  to  unite  with  different  bases. 
The  power,  therefore,  of  absorption  possessed  by  soils,  and  now 
under  investigation,  might  very  reasonably  be  supposed  to  reside 
in  the  alumina.  Whether  this  is  so  or  not  will  appear  as  we 
proceed ; but,  in  the  meanwhile,  it  will  be  observed  that  the  two 
experiments  which  have  been  just  described  are  much  opposed  to 
any  such  view. 
Up  to  this  point  the  experiments  that  have  been  described 
were  made  with  the  different  soils,  and  free  or  caustic  ammonia  : 
it  becomes  now  necessary  to  mention  the  effects  produced  by  soils 
upon  the  salts  of  this  alkali. 
Absorptive  power  of  soils  for  carbonate  of  ammonia  : — 
Experiment  36. — 500  grains  of  the  carbonate  of  ammonia  of  the  shops 
dissolved  in  16  ounces  of  water,  and  a stream  of  carbonic  acid  passed 
through  it  for  a quarter  of  an  hour.  This  solution  being  poured  upon  a 
column  of  12  inches  of  Mr.  Pusey's  soil,  began  to  drop  through  in  about 
an  hour,  and  after  more  than  an  ounce  had  passed  no  smell  of  ammonia 
was  perceptible  in  it,  nor  did  the  addition  of  caustic  potash  produce 
any.  It  is  worthy  of  notice  that  the  addition  of  potash  to  the  filtered 
solution  gave  a copious  precipitate,  which  proved  to  be  lime. 
Experiment  37. — A repetition  of  the  preceding,  with  the  same  result. 
Carbonate  of  ammonia  is  then  subject  to  the  same  absorption 
by  the  soil  as  the  caustic  alkali  : this  is  very  important,  since  the 
ammonia  existing  in  the  air  and  brought  down  to  the  soil  by  rain 
is  in  the  state  of  bi-carbonate  of  ammonia.  Great  part  of  the 
ammonia  produced  in  the  natural  decay  of  nitrogenized  manures  is 
also  in  combination  with  carbonic  acid.  The  practical  interest  of 
this  absorptive  property  of  soils  would,  therefore,  be  much  limited 
if  the  power  only  had  reference  to  the  free  alkali.  It  is,  how- 
ever, encouraging  to  be  able  to  depend  upon  this  power  for  the 
preservation  of  not  only  ammonia  and  its  carbonate,  but  of  all 
other  combinations  of  this  valuable  substance.  The  following 
experiments  have  reference  to  some  of  these  salts. 
Sulphate  of  ammonia : — 
Experiment  38. — 500  grains  of  sulphate  of  ammonia  dissolved  in  16 
ounces  of  water.  The  solution  was  slightly  acid  to  test-paper  ; Mr.  Pusey’s 
soil  as  a filter-bed  of  12  inches.  The  solution  of  sulphate  of  ammonia 
percolated  in  about  H hour;  the  first  portions  gave  no  indication  of 
ammonia  upon  the  addition  of  potash ; it  contained  from  the  first,  how- 
ever, abundance  of  sulphuric  acid  in  combination  with  lime.  Several 
ounces  were  collected  free  from  ammonia  or  its  salts,  but  the  quantity 
was  not  accurately  observed,  as  portions  were  used  from  time  to  time  for 
the  operation  of  testing. 
Experiment  39. — A filter-bed  of  18  inches  of  Mr.  Huxtable’s  soil,  with 
solution  of  sulphate  of  ammonia  of  unknown  strength,  but  giving  off 
