Abstract
As the pH of an aqueous solution of nitrous oxide is increased from 0.1 to 4,
G
(N
2
) for the
γ
-irradiated system increases sigmoidally from 0.75 to 3.1 and
G
(O
2
) from 0.1 ± 0.1 to 1.23 while
G
(H
2
) decreases from 0.45 to 0.2 and
G
(H
2
O
2
) decreases slightly. At all higher pH values
G
(H
2
) is constant, but
G
(N
2
) and
G
(O
2
) are constant only up to pH 11.2 when
G
(N
2
) increases suddenly by about one unit and
G
(O
2
) possibly undergoes a small increase. These data and the effect of pH on
G
(Fe
3+
),
G
(N
2
) and
G
(H
2
) for N
2
O-containing, de-aerated solutions of ferrous sulphate are explicable in terms of a primary act for
γ
-irradiated aqueous system s represented by the equation 4.5 H
2
O → 0.45 H
2
+ (0.8 - 0.015 pH ) H
2
O
2
+ (2.05 + 0.03 pH )OH + 2.75 H
a
+ 0.75 H
2
0*, where H
a
is an entity, stoiehiometrically equivalent to a hydrogen atom, which can react with N
2
O ultimately forming N
2
and an entity stoichiometrically equivalent to a hydroxyl radical. H
a
reacts with H
+
to form H
b
which reacts with N
2
O much more slowly than H
a
. H
2
O* is an excited water molecule which can revert to the ground state (lifetime > 10
-9
s) or react with sulphuric acid to form OH or its equivalent and H
c
, equivalent to a hydrogen atom and which can react with N
2
O in a manner similar to H
a
. All three species, H
a
, H
b
and H
c
can oxidize ferrous ions and reduce ceric ions in a stoichiometrically equivalent manner. Their possible identities are discussed and it is concluded that probably H
a
=
e
aq
., H
b
= H and H
c
= H
+
2
. The postulated existence of H
2
O* gives a rational description of the hitherto unexplained increases in G
OH
and ‘conventional’ G
H
which occurs at pH < 3.5. The ‘step’ in the curve of
G
(N
2
) against pH at 11.2 is attributed to ionic dissociation of the hydroxyl radical (→ H
+
+ O
-
) and the reaction O
-
+ N
2
O → (N
2
O
2
-
) → 1/2N
2
+ NO
-
2
.
Reference32 articles.
1. Allen A. O. H ochanadel C. J . Ghorm ley J . A. & D avis T. W . 1952 P hys. 56 575.
2. Studies in the Radiolysis of Ferrous Sulfate Solutions: III. Air-Free Solutions at Higher pH
3. Proceedings of Second Conference on the Peaceful Uses of Atom ic Energy;Allen A. O.;Geneva,1958
4. J . P hys;Allen A. O.;Chem.,1959
5. Z . P hys;Baxendale J .;Chem.,1958
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