70 
On  the  Absorbent  Power  of  Soils. 
This  was  a complete  surprise.  The  large  proportion  of  gyp- 
sum obtained  from  A (4  grs.),  when  compared  with  that  from  B 
(1  gr.),  showed  that  a considerable  portion  of  the  sulphate  of 
ammonia  mixed  with  the  soil  had  been  decomposed,  and  that  this 
process  was  in  some  way  connected  with  the  presence  of  lime  in 
the  soil,  as  the  sulphuric  acid  was  washed  out  in  combination  with 
lime.  To  test  the  extent  to  which  this  process  might  be  carried 
under  favourable  circumstances,  the  experiment  was  repeated  as 
follows  : 
Portions  of  the  same  soil  were  placed  in  the  percolators  to  the 
depth  of  8 inches.  Ten  grs.  sulphate  of  ammonia  were  intimately 
mixed  with  the  soil  in  one  (A),  ten  grs.  of  the  sesquicarbonate 
with  that  in  the  other  (B).  Three  fluid  ounces  of  water  were 
poured  upon  it,  and  two  similar  portions  at  intervals  of  three 
hours.  The  whole  of  the  filtered  liquid  was  returned  upon  the 
soil  at  the  end  of  twelve  hours,  and  the  same  process  repeated  at 
the  end  of  the  following  twelve  hours ; and  when  it  had  again 
passed  through  the  soil,  successive  portions  of  water  amounting  to 
8 ounces  more  were  passed  through.  The  whole  of  the  filtered 
liquid  was  neutralized  with  muriatic  acid  and  evaporated  nearly 
to  dryness,  then  treated  with  alcohol  and  filtered.  The  preci- 
pitate collected  on  the  filter  weighed  6^  grs.,  the  whole  of  which, 
with  the  exception  of  a mere  trace,  was  gypsum.  The  alcoholic 
solution  on  being  evaporated  and  heated  to  redness  gave  1 gr., 
chiefly  mur.  magnesia;  a mere  trace  of  ammonia  was  found  in  the 
solid  matter  derived  from  the  alcoholic  solution. 
B.  The  same  process  was  repeated  with  the  following  result: — 
Insoluble  in  alcohol  T\  gr.  nearly  all  gypsum. 
The  alcoholic  solution  evaporated  and  heated  to  redness  gave 
2|  grs.  (a  slight  trace  of  ammonia  perceptible,  apparently  not 
more  than  in  A).  The  2a  grs.  being  dissolved  in  water  and 
treated  with  sulph.  ammon.  and  alcohol,  gave  a copious  pre- 
cipitate of  sulph.  lime,  which  being  separated,  the  solution  was 
treated  with  ammonia  and  phosphate  of  soda,  giving  a precipitate 
of  aminonio-phosphate  of  magnesia. 
No.  2. 
Grains. 
. ( 6-3  sulphate  of  lime. 
\ 1 • muriate  of  magnesia. 
„ ( • 1 sulphate  of  lime. 
t 2-5  muriates  of  lime  and  magnesia. 
It  thus  appeared  that  when  the  absorptive  powers  of  the  soil 
were  fully  called  into  play,  by  passing  the  filtered  liquid  repeatedly 
through  the  percolators,  the  whole  of  the  ammonia  was  retained 
by  the  soil,  whether  applied  in  the  form  of  sulphate  or  sesqui- 
carbonate. The  cause  of  its  retention  will  be  again  adverted  to 
