333 
On  the  Power  of  Soils  to  absorb  Manure. 
Experiment  44. — Carbonate  of  potash.  Mr.  Iluxtable’s  soil  in  a tube 
18  inches  long ; through  this  a solution  of  carbonate  of  potash  of  un- 
known strength,  but  strongly  effervescing  with  acid,  and  giving  with 
platinum  solution  ready  evidence  of  the  presence  of  potash,  was  filtered  ; 
it  came  through  in  a few  minutes.  The  filtered  liquid  did  not 
effervesce  with  acids,  and  no  indication  of  potash  in  it  could  be  obtained. 
The  experiments  were  tried  comparatively  with  the  solution  before  and 
after  filtration,  and  the  result  was  not  in  the  least  doubtful. 
Experiment  45. — 20  grains  of  carbonate  of  potash  were  dissolved  in 
8 ounces  of  water.  The  solution  effervesced  strongly  with  hydrochloric 
acid,  and  gave  ready  evidence  of  potash  when  treated  by  chloride  of 
platinum.  It  was  poured  upon  a filter-bed  of  Mr.  Pusey’s  soil  10  inches 
in  depth.  When  an  ounce  and  a half  had  passed  through  the  liquid  was 
examined ; to  avoid  any  chance  of  error  three  separate  quantities  of  the 
original  and  resulting  liquids  being  tested  comparatively : the  results 
were  very  satisfactory,  and  proved  the  total  separation  of  the  carbonate 
of  potash  by  the  filtration. 
In  these  last  experiments  we  meet  with  the  unexpected  fact 
that  potash  and  its  carbonate,  which  in  the  liquid  way  form  very 
few  insoluble  compounds,  are,  by  a power  inherent  in  soils,  made 
insoluble  and  separated  from  water.  It  has  just  before  been  ex- 
plained that  the  power  of  soils  to  separate  ammonia  from  its  salts, 
wonderful  as  that  is,  might  have  existed  independently  of  any  such 
action  on  the  other  bases,  and  might  have  been  supposed  to 
depend  upon  a physical  law  of  condensation  for  ammonia  and  its 
carbonate  as  gaseous  substances.  That  such  is  not  the  case, 
however,  and  that  the  action  is  of  a purely  chemical  kind,  is  ob- 
vious from  the  last  experiments,  in  which  potash  and  its  carbonate, 
both  fixed  substances,  are  separated  from  solution  and  detained 
in  the  insoluble  form  in  a perfectly  analogous  way. 
We  shall  now  shortly  state  the  experiments  made  with  solu- 
tions of  other  potash  salts. 
Experiment  46. — Nitrate  of  potash.  100  grains  of  nitrate  of  potash 
were  dissolved  in  5000  grains  of  water  (I  part  in  50).  The  solution  was 
passed  through  a filter-bed  of  10  inches  of  Mr.  Pusey’s  soil ; it  came 
through  quickly,  and  contained  no  potash : nitric  acid,  however,  was,  by 
the  proper  tests,  found  to  have  passed  in  abundance,  and  existed  as 
nitrate  of  lime  in  the  filtered  liquid. 
Experiment  47. — A repetition  of  the  last,  with  the  same  results. 
Experiment  48. — A similar  experiment  with  Mr.  Huxtable’s  soil  and 
muriate  of  potash.  The  filtered  solution  contained  no  potash,  but  in  its 
place  plenty  of  lime  in  the  state  of  muriate. 
Experiment  49. — A solution  of  sulphate  of  potash  passed  through  Mr. 
Pusey's  soil.  The  resulting  liquid  contained  much  sulphate  of  lime,  but 
no  potash. 
1 he  salts  of  potash,  then,  seem  to  obey  precisely  the  same 
law  as  those  of  ammonia.  So  far  as  it  has  yet  appeared  the 
caustic  alkali  and  its  carbonate  are  in  each  case  absorbed  without 
change,  whilst  the  other  salts  only  part  with  their  base,  obtaining 
