Transfer Properties of Glycylglycine from Water to
Aqueous NaNO<sub>3</sub>, NaClO<sub>4</sub>, and Na<sub>2</sub>SO<sub>4</sub> Solutions
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Abstract
Enthalpies
of solution and densities of glycylglycine in aqueous
solutions of NaNO<sub>3</sub>, NaClO<sub>4</sub>, and Na<sub>2</sub>SO<sub>4</sub> were measured at 298.15 K. Standard transfer enthalpies
(Δ<sub>tr</sub><i>H</i><sup>0</sup>), standard transfer
partial molar volume (Δ<sub>tr</sub><i>V</i><sub>ϕ</sub><sup>0</sup>), and hydration
numbers (<i>N</i><sub>h</sub>) have been determined for
glycylglycine. All of the Δ<sub>tr</sub><i>H</i><sup>0</sup> values are negative in the three salt solutions. The relative
order of Δ<sub>tr</sub><i>H</i><sup>0</sup> in the
same concentration of 1–1 type salts is NaNO<sub>3</sub> >
NaClO<sub>4</sub>. The Δ<sub>tr</sub><i>H</i><sup>0</sup> in low concentration of Na<sub>2</sub>SO<sub>4</sub> solutions
is between the corresponding values in NaNO<sub>3</sub> and NaClO<sub>4</sub> solutions. With increasing Na<sub>2</sub>SO<sub>4</sub> concentration,
the Δ<sub>tr</sub><i>H</i><sup>0</sup> values exceed
that in NaNO<sub>3</sub> solutions. The Δ<sub>tr</sub><i>V</i><sub>ϕ</sub><sup>0</sup> values are positive and vary in the sequence Na<sub>2</sub>SO<sub>4</sub> > NaNO<sub>3</sub> > NaClO<sub>4</sub>. The
results
were discussed in terms of various interactions
