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In their “Comment on ‘Negative Deviations from the Debye–Hückel Limiting Law for High-Charge Polyvalent Electrolytes: Are They Real?’ ” Biver and Malatesta, citing my respective paper, argue that my analysis of experimental data of their group is wrong and so is my conclusion that negative deviations observed by them are not physically real. Here I rebut their arguments and explain why their rejection of my work is unjustified, and why those authors do not in any way prove me wrong. The core of my study and conclusion remains intact: Negative deviations in the case of high-charge electrolytes with |z+z–| > 3 do not always happen, and so far, such observed deviations are not convincingly supported by theory.

In the past few decades, electromotive force (emf, E) measurements using improved electrochemical cells have afforded the derivation of mean ionic activity coefficients(γ±’s) of very dilute solutions of binary electrolytes, within the 10–6–10–3molar range (Malatesta et al., J. Solution Chem.1994, 23, 11). Such measurements are especially important for highly charged electrolytes whose behavior at very low concentration is not yet fully understood, and whose γ±values, derived from Edata, have been claimed by Malatesta and co-workers to exhibit “negative deviations” from the Debye–Hückel (DH) limiting law. Here I examine electrolytes studied by the Malatesta group, which belong to the 3–1, 1–3, 2–3, and 3–3 valence families, and analyze their Eand γ±data using the Smaller-ion Shell (SiS) theoretical treatment (“DH–SiS”) of strong electrolyte solutions (Fraenkel, J. Chem. Theory Comput.2015, 11, 178and 193). The DH–SiS physical model incorporates all three ion-size parameters of a binary ionic solution as the “true” ion–ion collision distances, and leads to an improved DH-like electrostatic theory of ionic activity. Correcting Malatesta’s data by better extrapolation of Eto zero concentration results in a more accurate “standard potential”, E°; this affords improved γ±values that (1) fit well with the DH–SiS equations and (2) agree with the DH limiting law.

The present study compares the Monte Carlo (MC) simulation of the primitive model (PM) (Abbas, Z. et al. J. Phys. Chem. B2009, 113, 5905), by which activity coefficients of many binary ionic solutions have been computed through adjusting ion-size parameters (ISPs) for achieving best fit with experiment, with a parallel fit and ISP adjustment, employing the Smaller-ion Shell (SiS) treatment (Fraenkel, D. Mol. Phys.2010, 108, 1435), a Debye–Hückel type theory (“DH–SiS”) considering counterions of unequal size. DH–SiS is analogous to the unrestricted PM (UPM), so the comparison is with the MC simulation of the UPM, “MC–UPM”. Among the representative electrolytes NaCl, KCl, NaClO4, CaCl2, Ca(ClO4)2, and LaCl3, in water at 25 °C, the 1–1 electrolytes exhibit a far better fit quality for DH–SiS than for MC–UPM, and the fit extends to higher concentration. Moreover, theoretical single-ion activity coefficients derived from DH–SiS agree with experimental estimation for solutions of NaCl, CaCl2, and other electrolytes (Fraenkel, D. J. Phys. Chem. B2012, 116, 3603), whereas parallel MC–UPM predictions are at odds with experiment. Additional advantages of DH–SiS over MC–UPM are in (a) employing co-ion ISPs that are usually equal to the crystallographic ion diameters and (b) easily applying ISP nonadditivity in adjusting counterion ISPs.

Thermodynamic properties of aqueous HCl are of great importance in science, technology, and engineering. Ample experimental data exist on the activity and conductivity of the acid, and empirical expressions are offered as interpolation equations for computing those data at the desired concentration and temperature. The DH–SiS theory (FraenkelMol. Phys.2010, 108, 1435), extending the Debye–Hückel theory by considering the smaller-ion shell (SiS) around the chosen ion, has afforded successful fit to activity coefficients of aqueous and nonaqueous HCl solutions (FraenkelJ. Phys. Chem. B2011, 115, 557, 14634). Here, I analyze equivalent conductivities of the acid by the DHO–SiS theory (FraenkelPhys. Chem. Chem. Phys.2018, 20, 29896) that incorporates the SiS concept into the Debye–Hückel–Onsager theory. The interrelation of DHO–SiS and DH–SiS allows computation of activity from conductivity and vice versa. Thus, I propose recommended values of activity coefficients, equivalent conductivities, and pH of HCl(aq) within the concentration and temperature ranges of the paper’s title. These theoretical values accurately reproduce the corresponding experimental values, but they stem from analytic mathematical equations with no adjustable parameters, instead of from empirical or semiempirical expressions containing adjustable parameters and/or coefficients of no clear physical meaning.

In a recent article (Fraenkel, D. Chem. Phys. Lett.2021, 781, 138957), an argument was made and advanced that the derivation of the equivalent conductivity of ionic solutions, Λ, directly from the specific conductivity, S, is correct only for symmetric strong electrolytes; for asymmetric electrolytes, a scientifically more sound way of deriving Λ from Sis through the ionic conductivities, i.e., converting the specific ionic conductivity, σi─after being redefined to include the effect of the counterion─to the equivalent ionic conductivity, λi. That article, as a Letter, was limited to ions of valence 1 and 2 at 25 °C. Here, the study is extended to electrolytes with ions of higher valence (3, 4) and temperatures other than 25 °C. The proposed method of indirect S-to-Λ conversion is shown to be broader, and it is further elaborated upon and discussed.

In a continuous-flow differential microreactor, sulfated zirconia (SZ), deliberately activated in situ by water, has converted methane at 673 K to a C2–C6hydrocarbon mixture of which 65–70% was ethene and isobutane. Maximum conversion activity of ∼4.6%, corresponding to 4 × 104mole methane reacted per mole sulfate per second, was attainable at S/(added H2O) molar ratio of 3.0 and methane flow rate of 5.6 × 106mol (g-SZ)−1s−1. This methane conversion could be catalytic and may involve superacidic sites.

Abstract: In a continuous-flow differential microreactor, sulfated zirconia (SZ), deliberately activated in situ by water, has converted methane at 673 K to a C2–C6 hydrocarbon mixture of which 65–70% was ethene and isobutane. Maximum conversion activity of ∼4.6%, corresponding to 4 × 104 mole methane reacted per mole sulfate per second, was attainable at S/(added H2O) molar ratio of 3.0 and methane flow rate of 5.6 × 106 mol (g-SZ)−1 s−1. This methane conversion could be catalytic and may involve superacidic sites.

The kinetics of the catalytic conversion of isobutane under gas-phase fixed-bed flow conditions over sulfated zirconia (SZ), when compared with those of other strong solid acids of known acidity, suggests that SZ may be a very strong solid superacid; this conclusion disagrees with recent reports claiming that SZ is not a superacid, and supports older claims, based on acidity tests with Hammett indicators, that SZ may have H0of < −16.

An unlinked suppressor mutation, pfkB1,was reported to restore fructose 6-phosphate kinase activity to fructose 6-phosphate kinase mutants (e.g. pfkA1; Morrissey, A. T. E., andFraenkel, D. G. (1972) J. Bacteriol. 112, 183). We show here that a strain wild type at the pfkAlocus and also carrying the suppressor mutation contains two readily separable enzyme activities. Activity 1 resembles the known allosteric wild type enzyme, and activity 2 does not show allosteric characteristics.