On  the  Power  of  Soils  to  absorb  Manure. 
361 
Experiment  8G. — A yellow  clay  from  Cornwall  was  boiled  with  hydro- 
chloric acid  for  an  hour,  and  subsequently  digested  with  the  acid  at  a 
high  temperature  for  24  hours.  The  acid  being  poured  off,  the  clay  was 
repeatedly  washed  with  distilled  water,  and  finally  dried  ; it  was  after  this 
treatment  quite  white,  oxide  of  iron  and  alumina  having  abundantly  dis- 
solved in  the  acid  liquid. 
Solution  of  Caustic  Potash  of  1 per  Cent. 
2000  grains 
1 Digested  in  th 
Acid-treated  Clay  . 
. 500  , , 
j for  2 hours. 
1st  Analysis  of  the  resulting  Liquid — 
Grains. 
Platinum  Salt. 
Potash. 
Per  Cent. 
160-96 
gave  4-07 
= -7854 
or  -4881 
2nd  Analysis — 
166-07 
gave  4 • 07 
= -7856 
or  -4730 
1st  Analysis 
2nd  , , 
•4881  per  Cent. 
•4730 
Mean  . . . '4805 
100  grains  of  the  original  Solution  contained  1 *0023  grains  of  Potash. 
100  grains  of  the  resulting  Solution  contained  ‘4805  , , , , 
Loss  by  each  100  grains  of  Solution  . ‘5218  , , , , 
The  whole  quantity  (2000  grains)  would  therefore  have  lost  10-436 
grains,  which  has  been  absorbed  by  500  grains  of  clay,  making  the  absorp- 
tion 2 '087  per  cent. 
The  last  experiment  exhibits  a clay  which,  after  being  boiled 
in  acid,  absorbs  twice  as  much  potash  as  the  one  previously 
examined,  and  it  may  be  assumed  that,  had  the  experiment  been 
tried,  this  clay  in  its  natural  state  would  have  been  equally 
active.  On  the  other  hand,  it  has  been  shown  (Experiment 
80  a)  that  in  the  power  to  separate  ammonia  from  its  salts 
this  clay  in  its  natural  condition  is  comparatively  deficient;  so 
that  we  have  a further  illustration  of  the  fact  that  the  absorption 
for  free  alkalis  and  for  the  salts  of  these  bases  is  in  many  cases 
of  very  different  intensity,  and  due,  therefore,  to  an  entirely  dis- 
tinct condition  in  the  soils. 
The  preceding  experiments  are  sufficient  to  give  an  outline  of 
the  extent  of  power  possessed  by  the  soil  for  the  absorption  of 
potash,  and  it  would  serve  very  little  purpose  to  have  extended 
them  to  other  salts  of  this  base,  which  obviously  would  be 
governed  bv  the  same  general  law. 
O j o 
Absorption  of  Lime. 
It  has  been  before  stated  that  the  salts  of  lime  generally  are 
not  subject  to  alteration  or  detention  when  filtered  through  soils. 
These  salts  are  indeed  products  of  the  decomposition  by  the  soil 
of  those  compounds  which  are  subject  to  its  influence,  muriate 
of  ammonia  or  sulphate  of  potash  yielding  corresponding  salts  of 
lime  when  placed  in  contact  with  the  soil.  The  only  solutions 
of  lime  which  come  under  the  absorbing  power  of  soils  are  those 
of  free  lime  itself  and  of  the  bi-carbonate.  The  following  ex- 
