Relation between the temperature of maximum density and partial compressibility of aqueous solutions of non-electrolytes

Abstract

By using the thermodynamic identity ∂//_∂p[(∂V//_∂T)_p]∂//_∂T[(∂V//_∂p)_T] it has been possible to derive a relationship between the pressure derivative (∂/∂p)(Δθ) of the shift in temperature of maximum density of water Δθ(=θ–θ₀, where θ₀= 3.98°C) and the temperature coefficient of the limiting apparent molal compressibility (d/dT)(ϕ^°_KS) for solutes in aqueous solutions. It is suggested that (∂/∂p)(Δθ), or better still (∂/∂p)(Δθ_str), which is in turn linked with temperature coefficient of apparent compressibility (∂/∂T)(ϕ_KS), can be a more subtle criterion for ascertaining the relative structure strengthening abilities of monofunctional organic solutes belonging either to the same or to different groups. Despite smaller volume losses for alcohols than amines, the former (according to the above criterion) turn out to be stronger structure stabilizers than the latter. Amines at infinite dilution appear to behave as structure breakers.