Chapter 3
Technetium Coordinated by Inorganic
Ligands in Aqueous and Nonaqueous
Solutions
Among the several oxidation states of technetium, which may be observed in organic
and inorganic media, the most stable and, consequently, the most important are +4
(as TcO 2 ) and +7 (as TcO
−
4 ). The transport properties of the latter were investigated
by Boyd (1978), Rard and Miller (1991) and Könnecke et al. (1997).
Table 3.1 presents the activity coefficients obtained for NaTcO 4 and HTcO 4 .
The data are taken from Rard and Miller (1991), who reevaluated earlier results
published by Boyd (1978). The activity coefficients for the highest acid concentration
were calculated using a graphical extrapolation from lower to higher concentrations
region. These authors assumed the following equation for osmotic coefficient, φ,
where A
∗
= 0.34733 (=A/(1.5)
3 ) kg
1/2 · mol
−1/2 at 25 °C is given by Eq. (3.1):
φ = 1 −
A
∗
|Z + Z − |
I m
×
1 + 1.5 ·
√ (I m )
− 2log e
1 + 1.5 ·
√ (I m )
−
1 + 1.5 ·
√
(I m ))
−1
+
p
i=4
A i−3 · m
i/4
(3.1)
and the activity coefficient, γ ± , where m stands for molality while A
is equal to
1.1722 mol
−1/2 ·kg
1/2 at 25 °C, can be given by Eq. (3.2) (Rard et al. 1999):
log e γ ± = −
A
|Z + Z − |
√
I m
1 + 1.5 ·
√
I m
+
p
i=4
(i/4 + 1)
i/4
· A i−3 · m
i/4
(3.2)
They also concluded that the above equations give the most accurate fit to the
experimental data when a least-square fitting is applied.
The results of the analysis taken by Rard turned out to be in good agreement with
data published later by Könnecke et al. (1997) who analyzed HTcO 4 and NaTcO 4 −
NaCl systems. They applied Pitzer’s approach in calculation of parameters describing
the interaction of ions (Pitzer 1991). The osmotic coefficient was calculated according
to Eq. (3.3). a w is water activity, M w is equal to 18.0152 g·mol
−1 and m i is the molality
© Springer Nature Switzerland AG 2021
M. Chotkowski and A. Czerwi´ nski, Electrochemistry of Technetium,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-62863-5_3
31
Technetium Coordinated by Inorganic
Ligands in Aqueous and Nonaqueous
Solutions
Among the several oxidation states of technetium, which may be observed in organic
and inorganic media, the most stable and, consequently, the most important are +4
(as TcO 2 ) and +7 (as TcO
−
4 ). The transport properties of the latter were investigated
by Boyd (1978), Rard and Miller (1991) and Könnecke et al. (1997).
Table 3.1 presents the activity coefficients obtained for NaTcO 4 and HTcO 4 .
The data are taken from Rard and Miller (1991), who reevaluated earlier results
published by Boyd (1978). The activity coefficients for the highest acid concentration
were calculated using a graphical extrapolation from lower to higher concentrations
region. These authors assumed the following equation for osmotic coefficient, φ,
where A
∗
= 0.34733 (=A/(1.5)
3 ) kg
1/2 · mol
−1/2 at 25 °C is given by Eq. (3.1):
φ = 1 −
A
∗
|Z + Z − |
I m
×
1 + 1.5 ·
√ (I m )
− 2log e
1 + 1.5 ·
√ (I m )
−
1 + 1.5 ·
√
(I m ))
−1
+
p
i=4
A i−3 · m
i/4
(3.1)
and the activity coefficient, γ ± , where m stands for molality while A
is equal to
1.1722 mol
−1/2 ·kg
1/2 at 25 °C, can be given by Eq. (3.2) (Rard et al. 1999):
log e γ ± = −
A
|Z + Z − |
√
I m
1 + 1.5 ·
√
I m
+
p
i=4
(i/4 + 1)
i/4
· A i−3 · m
i/4
(3.2)
They also concluded that the above equations give the most accurate fit to the
experimental data when a least-square fitting is applied.
The results of the analysis taken by Rard turned out to be in good agreement with
data published later by Könnecke et al. (1997) who analyzed HTcO 4 and NaTcO 4 −
NaCl systems. They applied Pitzer’s approach in calculation of parameters describing
the interaction of ions (Pitzer 1991). The osmotic coefficient was calculated according
to Eq. (3.3). a w is water activity, M w is equal to 18.0152 g·mol
−1 and m i is the molality
© Springer Nature Switzerland AG 2021
M. Chotkowski and A. Czerwi´ nski, Electrochemistry of Technetium,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-62863-5_3
31