357 
On  the  Forcer  of  Soils  to  absorb  Manure. 
The  whole  quantity  of  solution  (4000  grains)  would  therefore  have  lost 
8 ’732  grains  of  potash,  which  has  been  absorbed  by  2000  grains  of  clay, 
making  the  absorption  to  be  *4300  per  cent. 
As  was  expected,  the  quantity  of  potash  removed  from  solution 
by  a given  weight  of  the  clay  is  here  considerably  greater  than 
that  of  ammonia  under  similar  circumstances.  From  the  muriate 
of  ammonia  *2010  per  cent,  was  absorbed  by  the  clay;  the 
absorption  of  potash  is  as  above,  *4366,  or  more  than  double. 
Still  the  relation  of  equivalent  for  equivalent  is  not  attained  here, 
for  to  equal  *2010  per  cent,  (the  quantity  of  ammonia)  potash  to 
the  amount  of  • 5568  should  have  been  removed  by  100  grains 
of  the  clay. 
I am  inclined  to  think  that  by  further  experiments  the  cause 
of  this  aberration  will  be  satisfactorily  made  out,  and  that  it  in 
all  probability  depends  upon  a solubility  of  the  compounds  which 
are  formed  in  the  excess  of  the  salts  employed. 
In  the  filtration  of  a salt  of  potash  or  ammonia  through  clay  or 
through  a soil,  we  examine  the  liquid  that  first  passes,  and  can 
discover  no  trace  of  the  salt  employed.  If  our  observation  be 
correct,  it  is  evident  that  the  new  compounds  formed  in  the  soil 
are  not  in  any  degree  soluble  in  pure  water,  or  we  should  have 
some  portion  of  the  potash  or  ammonia  in  the  solution.  In  this 
method  of  making  the  experiment  we  have  evidently  the  soil  in 
excess,  but  when  the  soil  or  clay  is  digested  in  a solution  contain- 
ing more  of  the  alkali  than  it  can  take  up,  the  compounds  formed 
in  it,  whatever  they  may  be,  are  exposed  to  the  action  of  an  excess 
of  the  saline  solution , in  which  they  may  quite  possibly  be,  to  a 
certain  extent,  soluble.  The  character  of  the  resulting  solution 
would  therefore  be  modified  by  the  introduction,  to  a greater  or 
less  extent,  of  the  new  compounds. 
The  clearing  up  of  this  question,  as  of  many  others  connected 
with  the  subject,  can  hardly  be  expected  from  an  examination  of 
the  heterogeneous  compounds  with  which  we  have  to  deal  in  soils 
and  clays,  but  it  may  confidently  be  expected  to  follow  from  the 
experiments  which  are  being  made  to  isolate  and  produce  arti- 
ficially the  particular  ingredients  of  the  clay  to  which  the  power 
in  question  is  supposed  to  be  due. 
In  the  succeeding  experiments  a somewhat  stronger  solution  of 
potash  was  employed  : nitrate  of  potash  was  dissolved  in  water 
until  by  repeated  analysis  and  additions  of  the  salt  or  of  water  the 
solution  was  made  to  contain,  as  nearly  as  might  be,  1 per  cent, 
of  potash.  The  following  analyses  give  the  exact  strength  of  this 
solution  : — 
1st  Analysis — 
Grains.  Platinum  Salt.  Potash.  PerCent. 
233-97  gave  12-17  = 2-349  or  1-0040 
