334 
On  the  Power  of  Soils  to  absorb  Manure. 
lime  in  its  stead,  with  which  they  come  away  in  the  liquid.  We 
pass  on  now  to  salts  of  soda.  It  was  thought  unnecessary  in  this 
case  to  operate  upon  the  caustic  alkali,  and  the  only  solutions  em- 
ployed were  the  muriate  and  sulphate. 
Experiment  50. — A solution  of  sulphate  of  soda,  of  unknown  strength, 
but  affording  an  abundant  precipitate  by  nitrate  of  barytes,  and  strongly 
colouring  the  flame  of  a spirit-lamp,  was  passed  through  10  inches  of 
Mr.  Pusey’s  soil.  The  solution,  after  filtration,  contained  much  sulphate 
of  lime,  but  it  gave  scarcely  any  yellow  colour  to  the  flame.  The  lime 
being  precipitated  by  oxalate  of  ammonia,  and  the  solution  evaporated  to 
dryness  with  subsequent  heating  of  the  residue,  afforded  a small  portion 
of  a salt  which  wTas  probably  soda,  but  the  greater  part  of  the  soda  of  the 
salt  employed  had  undoubtedly  been  detained  by  the  soil. 
Similar  experiments  were  made  with  the  sulphate  of  soda  and 
white  clay,  and  with  muriate  of  soda  (common  salt)  and  Mr. 
Pusey’s  soil,  and  in  both  cases  an  absorption  of  the  alkali  was 
found  to  occur. 
Absorption  of  Lime. — The  experiments  which  have  been  de- 
scribed would  quite  lead  us  to  expect  that  the  ordinary  salts  of 
lime — the  muriate,  sulphate,  nitrate,  &c. — would  in  no  degree  be 
arrested  by  soils,  but  that  their  solutions  would  pass  unchanged 
through  the  filters  employed.  It  will  be  borne  in  mind,  as  has 
been  before  frequently  stated,  that  the  attraction  of  the  soil  is  for 
the  alkaline  or  earthy  base,  and  not  for  the  whole  salt.  But  this 
attraction  could  not  be  gratified  unless  some  other  base  were 
found  to  combine  with  the  acid,  for  it  is  inconceivable  that  the 
strong  mineral  acids  should  be  displaced  by  any  compounds  in  the 
soil.  We  have  seen  that  in  all  cases  where  a salt  is  filtered 
through  the  soil,  the  acid  comes  away  in  the  liquid  not  in  the  free 
state,  but  combined  with  lime,  which  it  has  taken  in  exchange  for 
its  previous  saturating  base  ; nor  can  we  for  a moment  suppose  that 
the  union  of  the  acid  with  lime  is  a secondary  and  accidental 
circumstance,  the  absorption  of  the  potash  or  ammonia  first  taking 
place,  and  the  liberated  acid  subsequently  meeting  with  lime  and 
dissolving  it.  Whatever  be  the  nature  of  the  combination  which 
occurs  between  the  ammonia  or  potash  and  the  soil,  it  cannot  be 
doubted  that  it  would  readily  be  destroyed  by  any  of  the  mineral 
acids,  even  in  a dilute  state.  The  combination  of  the  soil 
with  the  base  and  of  lime  with  the  acid  must  be  simultaneous, 
and  unless  the  lime  were  present  in  the  soil,  and  in  the  proper 
state  too,  no  kind  of  change  could  occur.  By  these  remarks  it 
will,  we  hope,  be  made  perfectly  plain  that  the  salts  of  lime  will 
in  no  way  be  subject  to  the  singular  law  which  we  are  discussing. 
Lime  is  the  saturating  base  provided  for  the  exercise  of  this  power 
upon  salts  of  the  other  alkalis  and  earths,  hut  for  its  own  salts 
there  is  no  provision.  It  does  not,  however,  follow  that  solution 
