.17 | 0.14 | 0.20
Phosphoric acid | 0.41 | 0.67 | 0.35 | 0.12 | 0.28 | 0.36
Ammonia | 0.26 | 0.12 | 0.15 | 0.44 | - | 0.24
Total nitrogen | 0.53 | 0.69 | 0.47 | 0.67 | 0.58 | 0.59
----------------+-------+-------+-------+-------+-------+---------

NOTE X. (p. 247).

THE NATURE OF THE CHEMICAL REACTIONS OF AMMONIA "FIXERS."

For the student, the exact nature of the chemical reactions taking place
may be of interest.

In the first place, it must be distinctly understood that the form in
which ammonia escapes from the manure-heap is not, as is so commonly
erroneously stated in agricultural text-books, as "free" ammonia.
Whenever ammonia is brought into contact with carbonic acid, carbonate
of ammonia is formed. When it is remembered that carbonic acid is by far
the most abundant of the gaseous products of the decomposition of
organic matter, it will be at once seen that free ammonia could not
exist under such circumstances.

1. In the case of _hydrochloric acid_, the following chemical equation
will represent the nature of the reaction--

2HCl + (NH_{4})_{2}CO_{3} = 2NH_{4}Cl + H_{2}O+CO_{2}
(Hydrochloric (carbonate of ammonia,) (sal-ammoniac,) (carbonic acid.)
acid,)

2. In the case of _sulphuric acid_, the equation will be--

H_{2}SO_{4} + (NH_{4})_{2}CO_{3} = (NH_{4})_{2}SO_{4} + H_{2}O+CO_{2}
(Sulphuric (carbonate of (sulphate of ammonia,) (carbonic acid.)
acid,) ammonia,)

3. With _gypsum_ (CaSO_{4})--

CaSO_{4} + (NH_{4})_{2}CO_{3} = CaCO_{3} + (NH_{4})_{2}SO_{4}
(Gypsum,) (carbonate of (calcium (sulphate of ammonia.)
ammonia,) carbonate,)

4. With _copperas_ (FeSO_{4})--

FeSO_{4} + (NH_{4})_{2}CO_{3} = FeCO_{3} + (NH_{4})_{2}SO_{4}
(Sulphate of (carbonate of (ferrous (sulphate of ammonia.)
iron,) ammonia,) carbonate,)

5. With _sulphate of magnesia_ (MgSO_{4})--

MgSO_{4} + (NH_{4})_{2}CO_{3} = MgCO_{3} + (NH_{4})_{2}SO_{4}
(Sulphate of (carbonate of (carbonate of (sulphate of
magnesia,) ammonia,) magnesia,) ammonia.)

Reference has been made to the fact that magnesium sulphate may probably
not only fix the ammonia, but the phosphoric acid. When magnesium
sulphate, soluble phosphoric acid, and ammonia are brought in contact
with one another, the double insoluble phosphate of ammonium and