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destabilizing the aggregates of dodecyl sulfate/metal ion. The non-occurrence of redis-
solution of lead alkanoates, under conditions of excess alkanoate is in agreement with
the lead(II) carboxylate bond having some covalency, and may indicate the existence
of weak interactions between the alkyl chains of the carboxylates.
FIGURE 4
Effect of sodium octanoate (Ƒ), sodium decanoate (ż), and sodium dodecanoate
(
Δ
) in the concentration of free Pb
2+
(in equilibrium) at 25ºC.
Assuming that the reaction between Pb
2+
and the carboxylates (C
n
COO
í
, with n =
7, 9, 11) can be described by Equation (1), the association constant,
K
a
, can be de¿ ned
by Equation (2):
Pb
2+
+ 2 C
n
COO
í
Pb(C
n
COO)
2
(1)
K
a
= [Pb(C
n
COO)
2
]
eq
/([C
n
COO
í
]
eq
2
[Pb
2+
]
eq
)
(2)
Considering the mass balance equations,
[Pb(C
n
COO)
2
]
eq
= [Pb
2+
]
i
- [Pb
2+
]
eq
(3)
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