Some comments on the paper “Effect of temperature on the partial molar volumes and viscosities of two macrocyclic aminals in water and deuterium oxide” by Carmen M. Romero and Holman J. Mesa [Journal of Molecular Liquids, 242 (2017) 244-248]

Recently, the above authors presented data on the apparent molar volumes and viscosities of solutions of two macrocyclic aminals, hexamethylenetetramine (HMT) and its dodecane-based analogue (TATD), in ordinary and heavy (D2O) water at four temperatures within a quite narrow interval from 293.15 K to 305.15 K. Noting the reported experimental results for TATD in the deuterium-substituted aqueous medium are of undoubted interest from the viewpoint of novelty of them, I found it necessary to debate the reliability of corresponding data for HMT. The point is that the authors did not consider it possible comparing their data on volume-related properties of the system (D2O + HMT) with those being available in the literature [Yu.P. Pankratov, V.K. Abrosimov, Russ. J. Phys. Chem. 71 (1997) 1263-1266]. Herewith, discussing the standard (at infinite dilution) molar volumes of HMT in ordinary water, the authors under comment (C.M. Romero and H.J. Mesa) have repeatedly referred to the specified work. Therefore, the question arose whether the existing data sets on volumetric characteristics of HMT in the H/D isotopically distinguishable aqueous media agree with each other. In this regard, using the results of mentioned and other researchers, I have carried out the comparative analysis of temperature-dependent values of standard molar volumes and expansibilities of HMT in both H2O and D2O. Two main points relating to the problem were considered here: how plausible is each of the compared “author's” volumetric characteristics relating to the H/D isotopically distinguishable aqueous media and how it is correlated with the predicted nature of the HMT hydration. Being found in the above sources, the pronounced inconsistencies in results of studying the standard molar volumes and expansibilities of the solute in both (H2O + HMT) and (D2O + HMT) point out the necessity for additional high-precise densimetry investigations of these binary liquid systems.