On  the  Power  of  Soils  to  absorb  Manure. 
351 
The  power  of  thoroughly  burnt  clay  to  absorb  ammonia  is 
therefore  very  small — indeed  so  small  that  it  would  be  unsafe  to 
found  our  belief  that  such  a power  actually  exists  upon  these 
experiments,  however  accurate  they  may  appear.  At  the  same 
time  it  will  be  recollected  that,  in  operating  upon  a filter-bed  of 
the  same  material,  there  appeared  to  be  a diminution  of  the 
strength  of  the  liquid,  and  consequently  an  absorption  of  the  am- 
monia by  the  filtering  medium.  There  can,  however,  be  no 
doubt  that  the  power  of  a clay  is  greatly  diminished  by  burning  ; 
that  it  is  not  destroyed,  but  only  reduced  to  one-half  by  a very 
considerable  heat,  is  ample  proof  that  the  absorptive  faculty  does 
not  reside  in  any  organic  or  other  compounds  destructible  by  a 
moderate  temperature. 
The  chalk  was  added  in  the  last  experiment  in  order  that 
nothing  might  be  wanting  to  the  absorption  of  ammonia  by  the 
powdered  pipe  in  case  the  power  was  possessed  by  it.  We  have 
before,  however,  seen  reason  to  believe  that  carbonate  of  lime  is 
not  necessary  in  any  case. 
Tobacco-pipes,  when  broken  up  and  sifted  through  a fine  sieve, 
gave,  as  before  stated,  a powder  which  would  not  separate  from  a 
solution  of  ammonia,  although  it  subsided  perfectly  from  the 
muriate.  By  the  use  of  two  sieves,  one  of  20  and  the  other  of  40 
holes  to  the  inch,  it  was  found  quite  easy  to  obtain  a powder 
which  readily  separated  from  ammonia,  and  offered  a means  of 
examining  the  action  of  highly  burnt  clay  upon  the  free  alkali  in 
solution. 
Experiment  75. — Powdered  tobacco-pipes  and  solution  of  ammonia. 
Powdered  tobacco-pipe  was  passed  ^through  a sieve  of  20  holes  to  the  inch  ; 
it  was  then  thrown  on  another  sieve  of  40  holes  ; only  that  portion  being 
used  for  the  experiment  that  was  detained  by  the  sieve.  This  was  further 
cleansed  from  adhering  powder  by  being  washed  in  distilled  water,  and 
then  perfectly  dried.  Of  course  in  this  form  it  readily  subsided  from  a 
liquid. 
Standard  Solution  of  Ammonia  4000  grains  1 tv  . , e . , 
Powdered  Pipe 2000  , , } D,SeSted  for  two  hours- 
1st  Distillation  of  the  resulting  Liquid — 
Grains.  Platinum  Salt.  Ammonia.  Per  Cent. 
352*50  gave  13*64  = 1*0406  or  *2924 
2nd  Distillation — 
175-69  gave  6-73  = -51309  or  -2920 
1st  Experiment . . . -2924  per  Cent. 
2nd  ,,  ...  -2920  ,, 
Mean  ....  *2922  , , 
100  grains  of  the  original  Liquid  contained  . *3173  grains  of  Ammonia. 
100  grains  of  the  resulting  Liquid  contained  -2922  ,,  ,, 
Loss  by  each  100  grains  of  Solution  . . *0251  ,,  ,, 
