ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPORT
The existence of these equilibria is coinpatible shown in ?able 6.11 were obtained. The pressure-
with Eq. ha, as may be seen from the fact that activity coefficient products in this table give the
AFY = AF; - AF;, K,,, = K ~ / K ~ Hence . it pressures which would be obtained if the solutions
woucd have been possible to derive Eq. Sa by using were ideal. Figure 1.23 shows the relative im-
equilibria 7 and 3. This is because the two sets portance of equilibria 1 and 2 in terms of the loga-
of equilibria 1 and 2 and equilibria 7 and 8 are
both equivalent to the one equilibrium
From Eq. 9 it will be noted that the pressure ratio
(Pt+20'PH2 )1,2
is determined by the competition
between the oxide and hydrogen for oxygen, with
the one trying to form the peroxide and the other
trying to form water.
In like manner, an expression analogous to Eq.
6a can be derived under the assumption that equi-
libria 1 and 3 determine the water and hydrogen
pressures, respectively. This expression is
K1,3 =--- ,
K3'l3
rithm of the pressure ratio as a function of the
reciprocal of the absolute temperature. Figure
6.21 gives the free energy differences (AF" and
1,2
AF" ) as functions of absolute temperature.
1,3
Examination of these data shows the following:
(1) Apart From unexpectedly large deviations from
ideality, equilibrium 1 will predominate at all
temperatures. (2) Assuming ideality, hydrogen
evolution from fused sodium hydroxide in an inert
container will be small at all temperatures, but it
should be measurable at 906°C. Likewise, the
peroxide concentration at al I temperatures may be
small, but it should be appreciable at 900°C. (3)
Deviations from ideality of a moderate amount
could make hydrogen and peroxide formation either
insignificant or greatly important at high temper-
atures.
62
54
46
38
r
~~
UNCLASSIFIED
ORPll -l-R-DNG 3033
30L - -
60 80 10 0 420 14 0 160
(!/TEMPERATURE) x io4 (OK)-'
By using the free energy data computed above Fig. 6.23. Decomposition Pressure Functions
for sodium hydroxide, the representative values for NaQaH.
1 06
Temperature AFY At.;
TABLE 6.11. DATA ON THE DECOMPQSlTlON OF SODIUM HYDROXIDE
("a (kcal) (kcal) K1 K2 K3
~.~~~...~~ _. ..~.
~~ ~
25 35.3 76.0 10 -26 10-56 10-95
600 21.4 64.4 4.7 x 10-6 10-18 10-27
(mm Hg)
~~~.~ .~ ..........
(mm Hg)
. . . . . . . . . -
1.7 7.4 x 10-6
900 13.5 59.9 3 x 1 ~ - 3 8 x lC-18 42.0 2.1