Calculation of henry constants for the adsorption of isomeric phenylenediamines on graphitized thermal carbon black

Henry constants for the adsorption of o- and p-phenylenediamines on the surface of graphitized thermal carbon black within the temperature range 433–479 K were calculated by the molecular statistical method. The parameters of the atom-atom potential function of intermolecular interaction between the nitrogen atom in aniline and isomeric phenylenediamines and the carbon atom of the basal face of graphite were determined. It was shown that an intramolecular H bond influenced the geometry and adsorption properties of o-phenylenediamine.     

An experimental and molecular-statistical study of the adsorption of the iodobenzene, 2-iodothiophene, and isomeric iodoadamantane molecules on the graphite basal face surface

The thermodynamic characteristics of adsorption of iodobenzene, 2-iodothiophene, and 1- and 2-iodoadamantanes on the surface of graphitized thermal carbon black were determined experimentally. The influence of the special features of the molecular structure of the adsorbates on the thermodynamic characteristics of adsorption was studied. The atom-atom approximation of the semiempirical molecular-statistical theory of adsorption was used to calculate the thermodynamic characteristics of adsorption of the adsorbates using the newly determined potential function parameters of pair intermolecular interaction (φ(r)) of I with C atoms of the basal graphite face. For the example of isostructural monohalogenated benzenes, thiophenes, and adamantanes, a comparative analysis of the contributions of the F, Cl, Br, and I atoms to the thermodynamic characteristics of adsorption was performed for the nonspecific adsorption of these compounds on a plane graphitized carbon black surface.     

The influence of an intramolecular H-bond on the adsorption of sulfur-containing amino acids on graphitized thermal carbon black

The thermodynamic characteristics of adsorption of sulfur-containing amino acids and their derivatives on the surface of graphitized thermal carbon black were calculated by the molecular statistical method. The parameters of the atom-atom potential function of intermolecular interaction between the S atom in amino acids and the graphite C atom were determined. It was shown that an intramolecular H-bond influenced the adsorption of amino acids on the surface of graphitized thermal carbon black.     

Thermodynamic characteristics of the adsorption of isomeric molecules of fluoroadamantanes on the surface of the basal face of graphite

The thermodynamic characteristics of adsorption (TCA) for isomeric molecules of mono-, di-, tri-, and tetrafluoroadamantanes were determined for the first time experimentally and by molecular statistics on the surface of graphitized thermal black (GTB). The parameters of atom-atom potential function of pair intermolecular interaction (φ(r)) for F atoms included in fluoroadamantanes with C atoms on the basal face of graphite were calculated for the first time within an atom-atom approximation of the semi-empirical molecular statistical theory of adsorption. The adsorption non-equivalence of F atoms in various positions of an adamantane framework, a consequence of the mutual effect of atoms in a framework molecule, was determined. On the basis of the definite TCA values, the conclusion was drawn as to the possibility of isolation of isomeric fluoroadamantanes under the conditions of gas-adsorption chromatography on GTB.     

On connection between conformational and thermodynamic properties of poly-2,4-dimethylstyrene in various solvents

The unperturbed chain dimensions K_θ of polydimethylstyrene (PDMS) in 12 solvents were determined by the Stockmayer-Fixman procedure. It was found that the value of K_θ decreased monotonously with increasing solvent power (i.e. with increasing the exponent a in the relation $\text{[η] = K}{}_{\mathrm{\eta }}\text{M}{}^{\mathrm{a}}$) The unperturbed chain dimensions in θ-solvent were obtained by extrapolation of log K_θ to $\text{a =}\text{1}\text{2}$. They are equal to 0·064. Analysis of data obtained both in aromatic and non-aromatic solvents showed that the decrease of the unperturbed chain dimensions was proportional to the product (βN_s): K_θ^1,3 = K_{θ.a = 1 2}^{1 3} (1 – 2·5 × 10²¹βN_s) (β is the excluded volume of the chain units and N_s is the mean number of the absorbed solvent molecules). The values of N_s were determined by light scattering in the series of mixed solvents. In the non-aromatic solvents, the unperturbed chain dimensions decrease with increase of the density of the molecular packing. It is suggested that interaction of neighbouring bulky side groups of the polymer chain is decreased by the solvent and this replaces the potential energy minimum of the chain in the direction of more folded conformations.     

Thermophysics of alkali and related azides II. Heat capacities of potassium,rubidium, cesium,and thallium azides from 5 to 350 K

The heat capacities of potassium, rubidium, cesium, and thallium azides were determined from 5 to 350 K by adiabatic calorimetry. Although the alkali-metal azides studied in this work exhibited no thermal anomalies over the temperature range studied, thallium azide has a bifurcated anomaly with two maxima at (233.0±0.1) K and (242.04±0.02) K. The associated excess entropy was 0.90 cal_th K^?1 mol^?1. The thermal properties of the azides and the corresponding structurally similar hydrogen difluorides are nearly identical. Both have linear symmetrical anions. However, thallium azide shows a solid-solid phase transition not exhibited by thallium hydrogen difluoride. At 298.15 K the values of C_p^o, S^o, and $\text{?{G}{}^{\mathrm{o}}\text{(T)?H}{}^{\mathrm{o}}\text{(0)}}\text{T}$, respectively, are 18.38, 24.86, and 12.676 cal_th K^?1 mol^?1 for potassium azide; 19.09, 28.78, and 15.58 cal_th K^?1 mol^?1 for rubidium azide; 19.89, 32.11, and 18.17 cal_th K^?1 mol^?1 for cesium azide; and 19.26, 32.09, and 18.69 cal_th K^?1 mol^?1 for thallium azide. Heat capacities at constant volume for KN₃ were deduced from infrared and Raman data.     

Cesium chromate,Cs2CrO4: heat capacity and thermodynamic properties from 5 to 350 K

The heat capacity of a sample of Cs₂CrO₄ was determined in the temperature range 5 to 350 K by aneroid adiabatic calorimetry. The heat capacity at constant pressure C_p^o(298.15 K), the entropy S^o(298.15 K), the enthalpy {H^o(298.15 K) - H^o(0)} and the function $\text{? {G}{}^{\mathrm{o}}\text{(298.15}\text{K}\text{) - H}{}^{\mathrm{o}}\text{(0)}}\text{298.15}\text{K}$ were found to be (146.06 ± 0.15) J K^?1 mol^?1, (228.59 ± 0.23) J K^?1 mol^?1, (30161 ± 30) J mol^?1, and (127.43 ± 0.13) J K^?1 mol^?1, respectively. The heat capacity C_p^o(298.15 K) and entropy S^o(298.15 K) and entropy S^o(298.15 K) of Rb₂CrO₄ are estimated to be (146.0 ± 1.0) J K^?1 mol^?1 and (217.6 ± 3.0) J K^?1 mol^?1, respectively.     

Thermodynamic parameters related to the specific adsorption of iodide ion on the mercury electrode

The thermodynamic functions for the specific adsorption of the iodide ion on mercury have been determined from capacity measurements at 5°C, 25°C and 45°C. The experimental values of the standard electrochemical free energy, enthalphy and entropy of adsorption at zero charge, Δ$\text{G}$⁰_I^?, Δ$\text{H}$⁰_I^?, and Δ$\text{S}$⁰_I^?, are in good agreement with previous values for chloride and thiocyanate ion adsorption. They show that most of the free energy change comes from the entropy change, suggesting that the structural contributions play an important role in the ion-specific adsorption. The thermodynamic functions are compared with the values calculated using the Andersen—Bockris model.     

Experimental and molecular-statistical investigation of adsorption of aminoadamantanes on graphitized thermal carbon black

Thermodynamic characteristics of adsorption of some isomeric aminoadamantanes on graphitized thermal carbon black were determined by molecular-statistic calculations and gas-chromatographic measurements. The parameters of the potential function for the pairwise intermolecular interactions between nitrogen in saturated amines and carbon in graphite were calculated. The best agreement between the experimental and calculated Henry constants for 1-aminoadamantane is attained by introducting a correction taking into account the influence of the cage effect on -substituents in the adamantane unit in the parameters of the _N...C(GTCB) atom-atom potential.     

The rotational spectrum and molecular properties of a hydrogen-bonded dimer of phosphine and hydrogen fluoride

⁵⁷Fe Mössbauer spectra have been obtained for Fe(p-CH₃C₆H₄SO₃)₂ between 2.3 and 300 K in zero field, and at 2.3 and 4.2 K in longitudinal applied magnetic fields ranging from 1.1 to 5.6 T. The complex is a fast-relaxing paramagnet under all conditions studied and there is no evidence of antiferromagnetic exchange coupling. The FeO₆ chromophore is distorted by a trigonal elongation and the orbital ground state is the [($\text{2}\text{3}$)^{$\text{1}\text{2}$}|±2〉 ? ($\text{1}\text{3}$)^{$\text{1}\text{2}$}|?1〉] doublet. The temperature dependence of the quadrupole splitting has been analysed via a crystal-field model to provide estimates of the axial field splitting parameter Ds = -93 cm^-1, spin-orbit coupling constant λ = -70 cm^-1, and fine structure constant Dσ = -28 cm^-1. The magnetic properties of the complex are described by treating the ground state as a non-Kramers doublet with fictitious spin ? = $\text{1}\text{2}$. Five separate Mössbauer-Zeeman spectra can be fitted in this spin-hamiltonian approximation with identical values of the g- and A-tensor components, viz. g_⊥ = 1.0, g_u = 9.0; A_⊥ ≈ 2.0 mm s^-1. A_u = -1.79 mm s^-1. The trigonal z axis, the z axis of the electric field gradient tensor, and the easy axis of magnetisation are collinear, and the saturation value of the internal hyperfine field along this axis is +13.0 T.     

A study of the near infrared emission bands of the hydroperoxyl radical at medium resolution

Emissions of the hydroperoxyl radical HO₂ in the spectral range from 1.0 to 1.6 μm were studied at low and medium resolution. The resolved spectrum shows the expected parallel band structure for the vibrational ovetone transition ²A″ (200-000); in the case of the vibronic transitions ²A′, 000 → ²A″, 000 and ²A′, 001 → ²A″, 000, however, comparison of experimental and computer simulated spectra shows that there also occur intense subbands with ΔK = 0, in addition to the ordinary ΔK = ± 1 transitions. The cause for the break-down of the type-C selection rule is not well known. In the reaction system of ethylene with discharged oxygen vibronic bands could be observed originating from ²A′ levels up to at least ν′₃ = 6. The most probable excitation mechanism for these high vibronic levels is the chemiluminescent reaction HCO + O₂ (¹Δ_g) → HO₂(²A′, 00ν′₂) + CO. From the computer fits to the spectra of HO₂ and DO₂ at medium resolution the origins of the 000-000 bands and the fundamental frequencies $\text{ν}$_3′ of the excited ²A′ state could be determined; the values are $\text{ν}$_o(HO₂)=7028 ± 3 cm^?1, $\text{ν}$_o(DO₂)=7034 ± 8 cm^?, $\text{ν}$_3′(HO₂)=927 ± 10 cm^?, and $\text{ν}$_3′(DO₂)=940 ± 28 cm^?1.     

Adsorption of nitrobenzene, aniline and nitroanilines on the surface of a basal face of graphite

Thermodynamic characteristics of the adsorption of nitrobenzene, aniline, and isomeric nitro-anilines are determined experimentally and from molecular statistics in the range of the closest packing of a graphite surface according to equilibrium gas adsorption chromatography. It is found that graphitized thermal carbon black is characterized by high selectivity upon the chromatographic separation of isomeric nitro-anilines (retention increases in the series of ortho, meta, and para isomers). Using the atom-atomic approximation of the semi-empirical molecular statistical theory of adsorption, parameters are calculated for the potential function of the pair intermolecular interaction of the NO₂ group in nitrobenzene and the N atom in aniline with the C atoms in a basal face of graphite. The effect of the NH₂ and NO₂ groups on the parameters of adsorption for isomeric nitroanilines as a result of direct polar conjugation is demonstrated and must be assumed when performing molecular statistical calculations.     

Calibration in quantitative analysis: Part 2. Confidence Regions for the Sample Content in the Case of Linear Calibration Relations

The precision of analytical results determined from linear calibration graphs is discussed. It is assumed that the standard deviation of the analytical procedure has the same value sx for all calibration levels and for the sample measurements. The collective and individual influence exerted by the number of both calibration and sample measurements (N and n, respectively) on the precision of the results is calculated on the basis of widths of confidence intervals. In addition, the effects on precision caused by the distribution of the calibration measurements over the calibration range and by the location of the sample in the analytical range are calculated. A quantity, comprising an “eccentricity term”, is developed, which contributes to better insight into the problems considered. For the special case that the k calibration levels are equidistant and the same number of replicate measurements m is made at each of these levels (km = N), the length of the confidence region is given by δx = 4s_x (n^-1 + z/N)^{$\text{1}\text{2}$} for α = 0.05. The value of z depends on the “eccentricity” of the sample value compared to the centre of gravity of the calibration values, and on the value of k. If the sample value coincides with the centre of gravity of the calibration values, z = 1. If the sample value coincides with one of the extreme values of the calibration experiments, the value of z increases to z = 2.00 for k = 2 and to z = 3.81 for k = 32.     

A theory of viscosity of dilute and moderately concentrated polymer solutions

A model theory of viscosity η for moderately concentrated polymer solutions is based on the assumption of a “local viscosity” effect and intermolecular hydrodynamic and thermodynamic interactions. It is shown that η is given by

$\text{η = η}{}_{\mathrm{o}}\text{{1 + γc[η]}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{·}\text{exp}\text{H}{}_{\mathrm{o}}\text{RT}\text{aø}\text{1 ? aø}$

where γ is 0–0.4 and depends on the quality of the solvent, a varies between 0,4 and 0.8 and depends on the fraction of the “free volume” of the systems, H₀ is the activation energy of the solvent and π is the polymer volume concentration. The dependence of η and “activation energy” of π and T for various molecular weights and qualities of solvents is described quantitatively. Anomalous dependences of [η] and of η on M for low polymer are obtained. An expression for η is proposed:

$\text{η}\text{η}{}_{\mathrm{o}}{}^{\mathrm{<mtext>1\; ?\; 2</mtext><mtext>K</mtext>}}\text{= {1 + (1 ? 2K)c[η]}F(π)}$

where K is the Huggins-Martin coefficient and F(π) = 1 for most solutions when T is > T_g. For poor solvents the H vs c curve (where H is the activation energy of η of solution) has a minimum value at moderate concentrations. For good solvents, H depends slightly on the molecular weight according to an empirical equation:

$\text{H = H}{}_{\mathrm{o}}\text{+}\text{660}\text{α}{}^3\text{1}\text{n}\text{η}\text{η}{}_{\mathrm{o}}$

Expressions are given from the viscosities of solutions of miscible and also solutions of immiscible polymers.     

Determination of the vapour pressures of o-, m-, and p-dinitrobenzene by the torsion-effusion method

The vaporization of o-, m-, and p-dinitrobenzenes was investigated by means of the torsion-effusion method and the selected equations for vapour pressure p as a function of temperature T are:

$\text{o-dinitrobenzene: log}{}_{10}\text{(}\text{p}\text{atm}\text{)=(7.03±0.34)?(4270±120)}\text{K}\text{T}\text{,m-dinitrobenzene: log}{}_{10}\text{(}\text{p}\text{atm}\text{)=(7.66±0.28)?(4400±100)}\text{K}\text{T}\text{,p-dinitrobenzene: log}{}_{10}\text{(}\text{p}\text{atm}\text{)=(8.34±0.34)?(4860±120)}\text{K}\text{T}$

The sublimation enthalpies ΔH^o(o-, 298.15 K) = (21.0 ± 0.5) kcal_th mol^?1, ΔH^o(m-, 298.15 K) = (20.8 ± 0.2) kcal_th mol^?1, and ΔH^o(p-, 298.15 K) = (23.0 ± 0.6) kcal_th mol^?1, are also derived by means of the second- and third-law treatments of the results.     

Neutron powder diffraction and magnetic measurements on TlMnI3 and TlFeI3

TlMnI₃ and TlFeI₃ are isostructural with NH₄CdCl₃. TlMnI₃ has a spiral structure which can be described with an incommensurable vector k, in the direction of the b1 axis of length 0.3614(5)b1. The spins lie in the (0 0 1) plane. TlMnI₃ exhibits antiferromagnetic behavior with a Néel temperature of 6.0(2) K. The exchange interaction was calculated to be $\text{zJ}\text{k}\text{= ?1.6}\text{K}\text{, z}$ being the number of nearest neighbors. Discontinuities in the magnetization are found for both the [1 0 0] and [0 1 0] directions at fields H^a_SF = 30.1(2) kOe and H^b_SF = 14.1(2) kOe. The magnetic structure of TlFeI₃ consists of puckered ferromagnetic (1 0 0) planes, which are coupled antiferromagnetically. The magnetic moments are parallel to the b axis. The Néel temperature is 21.5(3) K. $\text{zJ}\text{k}$ was found to be ?10(1) K with g = 2.68 and s = 2. The magnetic structures found for TlMnI₃ and TlFeI₃ are derived taking into account inter- and intra-double-chain interactions via two I^? ions.     

Adsorption of tetramethylsilane molecules on the basal face of graphite

The thermodynamic adsorption characteristics of tetramethylsilane (TMS) molecules on graphitized carbon black (GCB) were for the first time determined experimentally and by molecular statistics methods. The potential function parameters of pair molecular interactions (φ(r)) between Si and C atoms on the basal face of graphite were calculated in the atom-atom approximation of the semiempirical molecular-statistical theory of adsorption. The contributions of Si and C atoms to thermodynamic adsorption characteristics are compared for the example of nonspecific adsorption of TMS and isostructural neopentane molecules on the flat surface of GCB.