ON  NITROGEN  IN  MANURES  AND  SOIL. 
157 
a  balance  of  0-0303,  nearly  all  of  which  was  found  unappropriated 
in  the  soil. 
Finally  Boussingault  made  a  neat  series  of  comparative  experi- 
ments, introducing  into  calcined  sand  the  same  amount  of  phos- 
phate of  lime  and  carbonate  of  potash,  but  different  proportions 
of  nitrate  of  soda,  or  in  other  words  of  assimilable  nitrogen,  and 
watering  with  water  free  from  ammonia  but  containing  a  quarter 
of  its  volume  of  carbonic  acid.  The  soil  divided  among  four 
pots,  each  having  two  seeds  of  sunflower,  (II.  argophyllus  was 
the  species  used  in  all  the  experiments  ;)  the  pot 
No.  1  received  of  nitrate  of  soda,  0-00  grams. 
«  2  «        u  0-02  « 
«   3  "        "  0-04  « 
«  4  «       "  0-16  " 
The  results  of  fifty  days  vegetation  are  given  in  the  rate  of 
growth,  size  and  number  of  the  leaves,  weight  of  the  product. 
&c.  : 
No.  1  made  of  new  vegetable  matter,       0-397  grams. 
«   2  «  0-720  « 
«  3  «  1-130  « 
«  4  it  ,  3-280  « 
In  No.  2  so  little  as  three  milligrams  of  assimilable  nitrogen 
introduced  into  the  soil  enabled  the  plant  to  double  the  amount 
of  organic  matter.  The  proportion  of  the  weight  of  the  seeds 
to  that  of  the  plant  formed  was  in 
No.  1,    as    1  :  4-6  gr„ 
«   2,    «    1  :  7-6 
«  3,     «    1  :  11-3 
«  4,    «    1  :  30-8 
In  no  case  did  the  nitrogen  acquired  by  the  plant  exceed  that 
of  the  nitrate  added  to  the  soil. 
In  the  experiments  where  no  nitrate  was  added  to  the  soil,  the 
two  or  three  milligrams  of  nitrogen  acquired  by  the  plants  dur- 
ing three  months  of  vegetation,  came  in  all  probability  from 
ammoniacal  vapors  and  nitrates  existing  or  formed  in  the  atmos- 
phere. To  establish  their  presence,  Boussingault  arranged  an 
apparatus  which  detected  the  production  of  some  nitrates.  And, 
in  exposing  to  the  air  500  grams  of  calcined  sand,  which  had  10 
grams  of  oxalic  acid  mixed  with  it,  in  a  glass  vessel  with  an  open 
