To  illustrate :  Of  two  fertilizers,  A  and  B,  let  us  assume  that
A  contains  3.5  per  cent,  of  organic  nitrogen,  4.5  per  cent,  of
water-soluble,  3  per  cent,  of  citrate-soluble  and  i  per  cent,  of
insoluble  phosphoric  acid  and  6  per  cent,  of  potash,  and  sells
at  retail  for  $35.00.  B  contains  2.0  per  cent,  organic  nitrogen,
3.5  per  cent,  of  water-soluble,  3  per  cent,  citrate-soluble  and
4  per  cent,  insoluble  phosphoric  acid  and  8  per  cent,  of  potash,
and  retails  for  $32.00.
We  assume  that  both  are  in  good  condition,  sold  by  well-
known  and  reputable  manufacturers,  and  the  prices  are  the  best
obtainable  for  these  two  brands.  The  question  is,  which  is  the
better  purchase:  70  pounds  of  nitrogen,  150  pounds. of  soluble
phosphoric  acid,  20  pounds  of  insoluble  phosphoric  acid  and  120
pounds  of  potash  at  $35.00;  or  40  pounds  of  nitrogen,  130
pounds  of  soluble  phosphoric  acid,  80  pounds  of  insoluble  phos-
phoric acid  and  160  pounds  of  potash  for  $32.00.  Obviously  the
first  thing  to  do  is  to  get  the  approximate  value  of  all  these  sepa-
rate ingpredients  in  one  figure  so  as  to  have  some  common  basis  of
comparison.  In  a  ton  of  A  are  70  pounds  of  organic  nitrogen,
which  can  be  bought  for  about  19  cents  a  pound ;  150  pounds  of
soluble  phosphoric  acid,  which  can  be  bought  for  4>4  cents  per
pound  in  form  of  acid  phosphate ;  20  pounds  of  insoluble  phos-
phoric acid,  for  which  we  may  allow  2  cents  per  pound;  120
poimds  of  potash,  which  can  be  bought  in  form  of  muriate  for
4j4  cents  per  pound.
