H2O HCl Research Articles

Zircon solubility and zirconium complexation in H2O+Na2O+SiO2±Al2O3 fluids at high pressure and temperature

Zircon is an important host mineral for many high-field strength elements (HFSE), particularly Zr and Hf. Thus, its solubility in geologic fluids at high pressure and temperature plays an important role in terrestrial cycling of these elements during processes in the Earth's crust and mantle. We performed in-situ high-pressure, high-temperature measurements of zircon solubility in H2O–Na2Si3O7, H2O–Na2Si3O7+Al2O3, H2O–Na2Si2O5, H2O–NaAlSi3O8 fluids, as well as of baddeleyite solubility in H2O–NaOH fluids, by in-situ synchrotron radiation X-ray fluorescence analysis using hydrothermal diamond-anvil cells. Zirconium complexation in fluids in equilibrium with zircon was constrained by in-situ X-ray absorption near-edge structure (XANES) spectroscopy. Zircon solubility is strongly enhanced by addition of Na2Si3O7 to H2O. The degree of enhancement increases with Na2Si3O7 concentration. The Zr content of fluids containing 10wt% Na2Si3O7 reached up to 86±2ppm Zr at 550°C and 400MPa. At 30wt% Na2Si3O7, the maximum Zr concentration was 997±6ppm at 600°C and 440MPa. Zircon solubility in these fluids decreases considerably with pressure and increases slightly with temperature. Addition of Al2O3 decreases the zircon solubility. In H2O–NaAlSi3O8 fluids, the Zr concentrations are in the sub-ppm to ppm range. Zr concentrations in NaOH solutions in equilibrium with baddeleyite reached up to 390±2ppm at 600°C and 930MPa and increase with pressure and temperature. In-situ XANES spectra collected on Zr in H2O–Na2Si3O7, H2O–Na2Si3O7+Al2O3, H2O–NaOH, and H2O–HCl fluids in equilibrium with zircon provide evidence for strong differences in the Zr complexation between these fluids. Comparison of XANES spectra to those of model compounds and ab-initio simulation of XANES spectra revealed [8]Zr for the HCl solution, [7]Zr for the NaOH solution, and [6]Zr for the Na–Al-silicate-bearing solutions. For the latter solutions, formation of alkali zircono-silicate complexes is indicated by the strong dependence of zircon solubility on Na/Al and the similarity of the XANES spectra to spectra simulated based on the local structure around Zr in the alkali zircono-silicates vlasovite and catapleite. Alkali zircono-silicate complexes are responsible for the enhancement of Zr concentrations in Na–Al-silicate-bearing solutions and very likely play an important role for mobilization of HFSE during fluid–rock interaction. Because high alkali/Al can be expected in aqueous fluids at high pressure and temperature due to incongruent dissolution of feldspar and mica, the increase of zircon solubility along the NaAlSi3O8–Na2Si3O7 join points to potentially considerable Zr or HFSE transport by silicate-bearing aqueous fluids in the lower crust and upper mantle.

Solvent effects on the formation of different cadmium compounds from CdSO4, HCl and 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene

Abstract Solvothermal reactions of CdSO4·8/3H2O with 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb) and HCl in H2O, MeOH or EtOH afforded three coordination complexes [Cd5Cl2(μ-Cl)4(μ3-Cl)2(η,η,η-μ3-SO4)2(H2O)2(Htitmb)2]n (1), [Cd4Cl2(μ-Cl)2(η,η,η-μ3-SO4)2(MeOH)2(titmb)2]n (2) and [Cd4Cl2(μ-Cl)2(η,η,η-μ3-SO4)2] (3), respectively. All the compounds were characterized by elemental analysis, IR and single crystal X-ray diffraction. Compound 1 has a 1D chain in which each centrosymmetric double butterfly-shaped [Cd5Cl2(μ-Cl)4(μ3-Cl)2(H2O)2] unit interlinks with its equivalent ones via two couples of η,η,η-μ3-SO4 anions and two pairs of the Htitmb ligands. Compound 2 consists of one centrosymmetric [Cd5Cl2(μ-Cl)2(η,η,η-μ3-SO4)2(MeOH)4(titmb)2] unit that interconnects with equivalent ones via sharing Cd3 and its symmetry-related ones, forming a 1D zigzag chain. Compound 3 consists of a [Cd4Cl2(μ-Cl)2(η,η,η-μ3-SO4)2] unit linked by a pair of titmb ligands. The results may provide some insight into solvent effects on the formation of different coordination compounds from the same components.

Experimental metasomatism of monazite and xenotime: mineral stability, REE mobility and fluid composition

In this study a Th-bearing monazite from a Brazil beach sand, a low Th monazite from a Malawi carbonatite, and a xenotime from a pegmatite in northern Pakistan were experimentally metasomatised in a series of common metamorphic and igneous fluids at 600°C/500 MPa and 900°C/1000 MPa. Fluids included H2O, NaCl, and KCl brines, CaF2 + H2O, 1m and 2m HCl, 1m and 2m H2SO4, 1m NaOH, and Na2Si2O5 + H2O. The monazite show a variety of responses to the fluids ranging from no reaction (KCl + H2O) to small compositional changes and partial replacement of the monazite grain rim by Th-enriched monazite in the NaOH and (Na2Si2O5 + H2O) experiments respectively. The other acid and brine fluids induced varying degrees of partial dissolution in the monazite and xenotime, but no compositional alteration. Partial replacement of monazite grain rims by Th-enriched monazite occurred only in the alkaline fluids as the result of a coupled dissolution-reprecipitation process.

Microwave assisted extraction and hydrolysis: An alternative to pyrolysis for the analysis of recalcitrant organic matter? Application to a forest soil (Landes de Gascogne, France)

A comparison was made between the composition of the recalcitrant organic matter (ROM) isolated from a sandy forest soil, as revealed with microwave assisted extractions and/or hydrolysis, and using common pyrolysis techniques. Successive microwave irradiation treatments were performed in H2O, 0.1 and 1M HCl and 0.1 and 1M KOH. At each step the insoluble residue was examined via Curie point pyrolysis (CuPy) and Curie point thermally assisted hydrolysis and methylation (CuTHM). Sequential irradiation treatment resulted in ca. 35% degradation of the ROM. Compounds released on microwave irradiation in H2O and in HCl were dominated by glucose, suggesting the occurrence of carbohydrate-containing molecular associations in the soil organic matter (SOM) which were not disrupted during acid hydrolysis and extraction as applied for the isolation of the ROM. The product distribution from the microwave irradiation in KOH showed an important contribution to the ROM from the higher plant polyesters cutin and suberin, and to a lesser extent from lignin. Different lignin-derived compounds were specifically released upon microwave acid or base hydrolysis. This suggested that two types of lignin monomers, ether- or ester-linked, occurred in the ROM. The changes in the composition of the CuPy pyrolysates of the residues from the different microwave hydrolyses are consistent with the near complete removal of carbohydrates by microwave HCl hydrolysis. The changes in the composition of the CuTHM pyrolysates of the residues from the different microwave acid and base hydrolyses are in agreement with a major release of cutin- and suberin-derived compounds upon microwave KOH hydrolysis. The CuPy and CuTHM pyrolysates of the final residue consist predominantly of lignin-derived compounds. The study emphasizes the potential of microwave assisted hydrolysis to give a better estimate of the actual contribution of cutin to ROM than pyrolysis. However, the technique appears to be unable to completely release the lignin-based constituent of the ROM. Microwave irradiation appears to provide great potential as a tool for extraction and chemical characterisation of complex OM and could be an attractive additional technique to pyrolysis.

“Spontaneous” growth of fibrous products on the surface of silicic acid gels

We have observed occurrence of fibrous products on gel surface in four-component system of KK (silicic acid sol)–H2O–HCl–NH3, KK–H2O–HCl–NaOH and KK–H2O–HCl–TEA (triethanolamine). Bundles of fibres occur in the system with NH3, sticks and needles in system with NaOH, and finally in the system with TEA we can mostly observe the occurrence of crystalline products. Dependency of product morphology on initial sol composition is occurring in observed systems. In the case of system with NH3, mostly the length of nascent fibres is influenced by the composition, and in the systems with NaOH and TEA it is also final shape of nascent products. Morphology of nascent products in systems with NH3 and NaOH is controlled by quantity of added HCl, but in the system with TEA it is quantity of added TEA. It is characteristic for all observed systems that “spontaneously” occurring products consist of crystalline phase, that is chloride of respective alkali, and amorphous phase, that is SiO2. Beginning of respective chloride crystallization in observed systems probably initializes occurrence of products on gel surface. Further growth of crystals is influenced by present colloid of SiO2 that interacts with surface of growing crystal leading to anisotropy of its growth and therefore to “spontaneous” occurrence of fibrous products.

Model-Based Construction of Calcium Sulfate Phase-Transition Diagrams in the HCl−CaCl2−H2O System between 0 and 100 °C

Phase-transition diagrams of three CaSO4 phases, namely, dihydrate, hemihydrate, and anhydrate, in the HCl−CaCl2−H2O system are successfully constructed making use of a recently developed OLI-based chemical model. After initial validation of the model by comparison to experimentally determined CaSO4 phase-transition points in H2O or pure HCl solutions, the phase-transition border between dihydrate and anhydrite and that between dihydrate and hemihydrate was obtained by calculating the solution supersaturation (or scaling tendency according to OLI). The constructed phase-transition diagrams show three main regions, namely, regions I, II, and III. In region I, dihydrate is stable, while anhydrite is stable in regions II and III. Dihydrate is metastable in region II, while hemihydrate is metastable in region III. An increase in HCl and/or CaCl2 concentration causes the metastable region of HH to expand at the expense of DH. This has the result of lowering the corresponding transition temperatures.

Hydrothermal transformations of kaolinite at 200 and 250°C in the systems Li2O–Na2O–MgO–Al2O3–SiO2–H2O–HCl and Li2O–K2O–MgO–Al2O3–SiO2–H2O–HCl

AbstractThe hydrothermal reaction of kaolinite in the systems Li2O–K2O–MgO–Al2O3–SiO2–H2O–HCl and Li2O–Na2O–MgO–Al2O3–SiO2–H2O–HCl, at pH between 9 and 11, has been investigated at 200–250°C from 1 to 180 days.The X-ray diffraction study of the K-bearing system indicates that the solid products formed were Li-A(BW) zeolite, crystalline silica, and randomly ordered chlorite-smectite mixed layers, dioctahedral on average, with a chlorite:smectite ratio of ~1:4.Study by electron microscopy reveals, however, the presence of mixtures of very thin particles of smectite, di,trioctahedral chlorite and mixed-layer phases.The X-ray study of the solid products formed in the Na-bearing system reveals that the neo-formed phases were Li-A(BW) zeolite, analcime and partially ordered chlorite-vermiculite mixed-layers with high chlorite:vermiculite ratio. The transmission microscopic study of these phases shows the presence of dioctahedral ‘vermiculitic’ curved particles and di,trioctahedral chlorite-like particles.In both cases, long reaction times cause formation of a 7 Å phase with composition intermediate between kaolinite and serpentine.The composition of the solutions suggests that the stable phases would be chlorite/smectite mixed-layers, with compositions near tosudite in the case of the K-bearing reaction and both a dioctahedral phase (tosudite?) and a trioctahedral one (clinochlore) in the case of the Na-bearing reaction.

The connection between hydrogen diffusion through a steel membrane and mechanism of the hydrogen evolution reaction

AbstractThe kinetics of the hydrogen evolution reaction (HER) on Armco iron and carbon steel have been studied in the C2H4(OH)2H2OHCl system. The addition of 5–10% water or 1–10 mM Na2HAsO4 to the ethylene glycol solutions of HCl causes a transition from the Volmer rate determining step (rds) to the Tafel rds in the HER mechanism. According to experimental data, the rate of hydrogen diffusion through the carbon steel membrane does not depend on the rds nature of the HER. Theoretical analysis of the peculiarities of the Tafel rds has been carried out in which a recombination step was represented as a set of successive reactions. An expression has been obtained which determines the balance of surface processes and the hydrogen permeation into the bulk of the metal. It has been confirmed experimentally. Copyright © 2004 John Wiley & Sons, Ltd.

Photolabile Protecting Groups for Nucleosides: Mechanistic Studies of the 2-(2-Nitrophenyl)ethyl Group

The photochemistry of several 2-(2-nitrophenyl)ethyl-caged compounds including caged thymidine nucleosides was studied by nanosecond laser flash photolysis and stationary illumination experiments with quantitative HPLC analysis for quantum yields and product distribution. Effects of solvent basicity and acidity were investigated by varying the H2O content and HCl concentration, respectively, in MeCN/H2O mixtures. For all compounds 1 ‐ 7 investigated, intramolecular H abstraction by the nitro group from the exocyclic a-position with respect to the aryl moiety was found to be the primary process. The protolytic dissociation equilibrium of the resulting aci-nitro compound was kinetically characterized in the 0.1 ‐ 10 ms time region. In general, two reaction channels compete for the aci-nitro compound and its anion: b-elimination of the caged compound occurs from the anion, while from the undissociated aci-nitro compound, a nitrosobenzene derivative is formed with no release of the caged compound. The yield ratio of these two reaction channels can be controlled through shifts in the protolytic dissociation equilibrium of the aci-nitro compound. In solutions with either low basicity (H2O-free MeCN) or high acidity (higher concentration of HCl in H2O/MeCN), two as yet unidentified products are formed, each one specifically for one of the mentioned conditions.

Synthesis of tourmaline solid solutions in the system Na2O–MgO–Al2O3–SiO2–B2O3–H2O–HCl and the distribution of Na between tourmaline and fluid at 300 to 700 °C and 200 MPa

Tourmaline has been synthesized hydrothermally at 200 MPa between 300 and 700 °C from oxide mixtures with Mg–Al ratios for the end members dravite NaMg3Al6(Si6O18)(BO3)3(OH)3(OH) and Mg-foitite ❏(Mg2Al)Al6 (Si6O18)(BO3)3(OH)3(OH). Six different Na concentrations were investigated to determine the distribution of Na between tourmaline and fluid in the SiO2-saturated system Na2O–MgO–Al2O3–SiO2–B2O3–H2O–HCl. Synthetic tourmaline ranges from X-site vacant (❏) tourmaline (Mg-foitite) to nearly ideal dravite with Na=0.95 apfu. There are small, but significant, amounts of proton deficiency and negligible tetrahedral Al. Chemical variation is primarily caused by the substitutions Al❏Mg–1Na–1 and minor AlMg–1H–1. Varying amounts of Na and ❏ determine the Mg/Al ratios. Besides tourmaline and quartz, additional Mg–Al phases are chlorite and, at 700 °C, cordierite. Albite is also present at high Na concentrations in the bulk composition. The c dimension of the tourmaline crystals increases with Na in tourmaline. The amount of Na in the X-site depends strongly on the bulk concentration of Na in the system as well as on the temperature. These factors in turn control the phase assemblage and the composition of the fluid phase. For the assemblage tourmaline + quartz + chlorite/cordierite + fluid, a linear relationship exists between Na concentration in the fluid (quenched after the run) and tourmaline with temperature: T °C [±25 °C]=(Nafluid/Natur)×558.878-14.692 (r2=0.96).

Liquid-Phase Hydrogenation of 2-Ethylanthraquinone over Pd/Polyaniline Catalysts

The conjugated polymer polyaniline (PANI) has been used as the support for palladium catalysts. It was found that the dispersion of Pd in Pd/PANI catalysts depends on the nature of Pd2+–PANI interactions proceeding upon catalyst preparation. The type of interaction (protonation or oxidation–reduction process) was influenced mainly by the acidity of the precursor solution containing PdCl2–H2O–HCl. Under various conditions of acidity, two series of catalysts, A and B (0.8–10 wt% Pd), were prepared. In catalysts of series A, prepared using a strongly acidic solution (2 M HCl), the dispersion of Pd was high. On the other hand, in catalysts of series B, prepared using a weakly acidic PdCl2 solution (0.66×10−3 M HCl), large Pd particles (100–600 nm) were present. They were formed as the result of an oxidation–reduction process proceeding with the participation of PANI chain. The physicochemical properties of catalyst were characterized by XRD and SEM methods. All catalysts exhibited activity in 2-ethylanthraquinone (eAQ) liquid-phase hydrogenation. The catalysts of series A were more active and the selectivity of eAQ hydrogenation in their presence was higher than that seen for catalysts of series B.

Comparison of basis set superposition error corrected perturbation theories for calculating intermolecular interaction energies

Recently, two different but conceptually similar basis set superposition error (BSSE) free second-order perturbation theoretical schemes were developed by us that are being based on the chemical Hamiltonian approach (CHA). Using these CHA-MP2 and CHA-PT2 methods, a comparison is made between the a posteriori and a priori BSSE correction schemes at the correlated level. Sample calculations are presented for four hydrogen bonded complexes (HFH3N, HFH2O, H2SHF, and H2OHCl) in nine different basis sets (from 6–31G to TZV**++). The results show that the BSSE content is very significant in the interaction energy if electron correlation is accounted for, so removing the BSSE is very important. The differences of the two perturbational theories discussed are connected solely with the different one electron orbital sets used for building up the unperturbed single determinant wave function. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 274–283, 1999

Raman spectra of oligomeric species obtained by tetraethoxysilane hydrolysis-polycondensation process

Abstract By varying the molar water alkoxide ratios R, (0.5 ≤ R ≤ 1.75), the progressive hydrolysis and polycondensation of tetraethoxysilane (TEOS) in acidic medium (HCl 0.03 M) were investigated. In order to appreciate the effects of the alcohol on the reactions involved, part of the solutions were prepared with different amounts of ethanol. The identification of the intermediate products obtained under these experimental conditions was carried out with the help of vibrational spectroscopies (Raman and infrared) combined with 29Si nuclear magnetic resonance. In the case of the solution prepared without alcohol and for R = 0.5, the intensity of the Raman band characteristic of the monomer TEOS, appearing at 650 cm−1 and assigned to the symmetric SiO4 stretch, was invariant for reaction times (tR ranging from 24 to 123 h. This fact led us to maintain the tR parameter at 24 h for all the samples prepared without alcohol. However, the initial presence of ethanol, even in low quantity, in the systems studied (TEOSH2OHCl) induces more advanced hydrolysis-polycondensation reactions after a tR less than 24 h. The analysis of the solutions with 0.5 ≤ R ≤ 1 showed that traces of the monomer and its simple hydrolysis products were still detected. Concurrently, the intensity of the band characteristic of the dimer arising at 600 cm−1 increased. For larger values of R (R ≥ 1.25), the shift of this band from 600 to 530 cm−1 revealed the presence of more condensed species such as trimers (570 to 550 cm−1), branched trimers and polymeric structures (550 to 530 cm−1).

Relaxation of vibrationally excited HCl molecules in the H2O–HCl collision complex

The temperature dependence of the relaxation of HCl(v=1) by H2O in a complex-mode collision is studied in a semiclassical approach. The de-excitation probability takes a maximum value near room temperature, and it decreases logarithmically with increasing temperature. The dependence is nearly linear. Below room temperature, the relaxation becomes less efficient. This unusual temperature dependence is a result of the vibrational relaxation occurring in complex-mode collisions, which are dominated by large impact parameter interactions. The principal pathway for the removal of vibrational energy is the H–Cl oscillatory and librational motions along the O–H–Cl configuration. When these hindered motions gain the energy, they undergo transitions to free rotational states. The decreased energy transfer efficiency at low temperature is due to the slowing of rotational motions. Energy transfer to the O–Cl large-amplitude motion is of minor importance.

Regulation of the chlorine content in fresh, regenerated and coked PtRe/Al2O3 catalyst

AbstractIn bifunctional naphtha reforming catalysts the regulation of the chlorine content in order to equilibrate both catalytic functions (metallic and acidic) is one of the most relevant topics. In this paper a study of the chlorine regulation in fresh, regenerated and coked samples of a given commercial Pt (0.3 wt%)—Re (0.3 wt%)/Al2O3 catalyst is presented. Results show that an equilibrium chlorine content is reached when the samples are treated with an H2O—HCl mixture vaporized in a gas carrier (air or H2). This equilibrium content depends on the H2O/HCl molar ratio and the temperature of the regulation treatment. For fresh samples the equilibrium chlorine content does not depend on the nature of the gas carrier. Moreover, the retention capacity of chlorine by the support per unit of surface area is the same for fresh and regenerated samples. The presence of different amounts of coke on the surface does not modify the chlorine uptake with respect to the sample without coke.

In vitromultiplication of female date palm (Phoenix dactyliferaL.)

SummaryThe commercial propagation of date palm is through offshoots only, although these species can be multiplied by seeds also. Date palm being dioecious tree, the seed progeny, however, would have large number of male plants and the female plants too may be genetically heterogenous. This necessitates the propagation of date palm through offshoots. Unfortunately, number of offshooys in mother palm trees is also limited. Use of plant tissue culture techniques for fast multiplication of date palm, therefore is being considered by several tissue culture laboratories.A method has been developed to regenerate large number of plants from callus established from axillary buds and shoot tips of 3–4 year old offshoots in two varieties of date palm—Medjool and Khadravi. Best results were achieved when these ex-plants were cultured on a modified MS medium containing activated charcoal (0.3 %), Na H2PO4.2H2O (170 mg/l), KH2PO4.2H2O (200 mg/l), 2,4-D (100 mg/l), BAP (5 mg/l) and thiamine Hcl (1 mg/l). Whole plants have been regenerated through somatic embryogenesis. Cell suspensions were also initiated from leaf ex-plants obtained from intact offshoots. These could be further used for regenerating plants. This technique has great potential for multiplying superior genotypes which have lost the ability of normal offshoot formation.The regenerated plants were transferred to pre-sterilized soil containing farm yard manure and clay—sand mixture is small pots. High humidity, regular fungicide application and 2–3 hours of sun light everyday were some of the major requirements for proper growth of the young plants. New leaves and roots appeared in 1 -2 months in about 60% of the transplanted plants. These were then transferred to field conditions.

ChemInform Abstract: Synthesis and Characterization of New Mixed Oxohalides of Antimony and Tellurium.

AbstractSbTeO3Cl (I) can be prepared by solvolysis of a 1:1 mixture of TeCl4 and SbCl3 in H2O, aqueous NH3, or aqueous HCl.

Structure, energetics, and vibrational spectrum of H2O–HCl

H2O–HCl is studied using a number of basis sets including 6-31G** and variants which are augmented by a diffuse sp shell and a second set of d functions on O and Cl. Optimization of the geometry of the complex is carried out including explicitly electron correlation and counterpoise correction of the basis set superposition error (BSSE) at both the SCF and correlated levels. Correlation strengthens and shortens the H bond while BSSE correction leads to an opposite trend; these two effects are of different magnitude and hence cancel one another only partially. ΔH°(298 K) is calculated to be −4.0 kcal/mol, 1/4 of which is due to correlation. Formation of the complex causes the strong intensification and red shift of the H–Cl stretching band normally associated with H bonding, whereas the internal vibrations of H2O are very little affected, except for a doubling of the intensity of the symmetric stretch. With respect to the intermolecular modes, the bends of the proton donor are of higher frequency than those involving the acceptor. While these intermolecular bends are all of moderate intensity, comparable to the intramolecular modes, the H-bond stretch νσ is very weak indeed, consistent with a principle involving subunit dipoles. All calculated vibrational data are in excellent agreement with the spectra measured in solid inert gas matrices.

Theoretical study of H2O–HF and H2O–HCl: Comparison with experiment

The H bonds in H2O–HF and H2O–HCl are studied and compared using ab initio molecular orbital methods and the results compared to experimental data. Basis sets used are: (i) triple valence 6-311G** and (ii) double ζ with two sets of polarization functions. Electron correlation, included via second- and third-order Mo/ller–Plesset perturbation theory, is found to have profound effects on both systems, particularly H2O–HCl. Both H bonds are strengthened substantially with a concomitant reduction in length. H-bond energies and geometries calculated at correlated levels are in excellent accord with available experimental information. In both systems, all levels of theory indicate the equilibrium geometry contains a pyramidal arrangement about the oxygen atom. However, the difference in energy between this structure and a C2v planar arrangement is found to be small enough that consideration of probability amplitudes in the ground vibrational level leads to nearly equal likelihood of observing either geometry. Agreement between experimental vibrational frequencies in H2O–HF and those calculated at correlated levels and involving quadratic, cubic, and quartic force constants is quite good. An explanation is offered for the increase in HX bond length which occurs at SCF and correlated levels upon H-bond formation based upon nearly linear relationships between this length on one hand and subunit dipole moment and polarizability on the other. The dispersion energy is found to be a very sensitive, almost exactly linear function of the increase of H–X bond length. This energy contributes substantially to the weakening of the HX bond upon complexation.

Far-infrared bandshapes and angular motion of HCl, H2O and D2O in solutions

The reorientational correlation functions and the rotational—velocity correlation functions of HCl in CCl4, H2O and D2O in C6H6 have been obtained from the observed bandshapes of far-infrared absorptions. Both functions have positive humps at the same time. This fact indicates a librational nature of angular motion due to correlation among a few successive collisions. These functions are compared with the correlation functions of the free rotor. The time constants related to the angular motion and mean angles of free rotation are estimated.