Mixing Enthalpy for Binary Mixtures Containing Ionic Liquids

A complete review
of the published data on the mixing enthalpies
of mixtures containing ionic liquids, measured directly using calorimetric
techniques, is presented in this paper. The field of ionic liquids
is very active and a number of research groups in the world are dealing
with different applications of these fluids in the fields of chemistry,
chemical engineering, energy, gas storage and separation or materials
science. In all these fields, the knowledge of the energetics of mixing
is capital both to understand the interactions between these fluids
and the different substrates and also to establish the energy and
environmental cost of possible applications. Due to the relative novelty
of the field, the published data is sometimes controversial and recent
reviews are fragmentary and do not represent a set of reliable data.
This fact can be attributed to different reasons: (i) difficulties
in controlling the purity and stability of the ionic liquid samples;
(ii) availability of accurate experimental techniques, appropriate
for the measurement of viscous, charged, complex fluids; and (iii)
choice of an appropriate clear thermodynamic formalism to be used
by an interdisciplinary scientific community. In this paper, we address
all these points and propose a critical review of the published data,
advise on the most appropriate apparatus and experimental procedure
to measure this type of physical-chemical data in ionic liquids as
well as the way to treat the information obtained by an appropriate
thermodynamic formalism.