magnesium  is  used  with  soils  high  in  organic  matter.)  The  contents
of  the  bomb  are  then  washed  into  a  beaker  by  means  of  a  fine  stream  of
hot  water  and  brought  to  a  boil  to  break  up  the  coarse  particles  and  expel
as  much  oxygen  as  possible.  It  is  then  run  from  a  separatory  funnel  into
a  flask  containing  dilute  sulfuric  acid  (i  H2SO4  to  2  H2O)  and  the  gas
collected  in  a  measuring  pipette.  When  all  of  the  sample  has  been  added
to  the  sulfuric  acid  and  boiled  until  it  is  decomposed,  the  flask  is  filled
with  water  through  the  separatory  funnel  to  force  the  last  of  the  gas  into
the  measuring  pipette.  After  noting  the  volume,  the  carbon  dioxid  is
absorbed  in  the  potassium  hydroxid  pipette  and  the  volume  again  read.
In  taking  the  initial  and  the  final  readings,  the  same  precaution  should
be  taken  as  for  carbonate  carbon.  Duplicate  samples  should  check
within  i  cc.  for  every  100  cc.  gas  obtained,  and  corrections  must  be  made
for  pressure  and  temperature.
A  blank  determination  must  be  run  on  the  sodium  peroxid,  and  this  is
best  done  by  using  first  a  2-gram,  then  a  i-gram  sample  of  the  same  soil,
calculating  the  amount  of  carbon  in  the  reagents  from  the  difference  in
results,  e.g.
Let  x  =  carbon  in  reagents ;

then,  if  2  g.  soil  +  x  =  45  mg.  C,

and  i  g.  soil  +  x  =  25  mg.  C,

we  get  by  multiplying  the  last  equation  by  2

2  g.  soil  +  2  x  =  50  mg.  C,

and,  subtracting  the  first  equation  from  this,  we  get

x  =  5  mg.  C

Much  better  results  can  be  obtained  by  determining  the  blank  in  this
way  than  where  no  soil  is  used.
