Apparent molal volumes of butylammonium chlorides and sodium butanecarboxylates in dilute aqueous solutions

The densities of dilute aqueous solutions of the isomers of butylammonium chlorides (n-, iso-, sec-, andtert-BuNH₃Cl) and sodium butanecarboxylates (n-, iso-, sec-, andtert-BuCOONa) have been determined at 5, 25, and 45°C using a buoyancy technique. The limiting partial molal volumes \(\bar V^\circ\) and expansibilities of the solutes have been evaluated. The branching of alkyl chain causes larger \(\bar V^\circ\) values for BuNH₃Cl series but smaller values for BuCOONa series. The \(\bar V^\circ\) values of branched isomers have been calculated using the data for volume increment accompanying methyl substitution. Good agreement with the experimental values was obtained. It is suggested that the volumetric behavior of the organic electrolytes studied is governed by the influences of the ionic groups on the hydrophobic hydration. The results have been compared with the data for butanol isomers.     

Half-width and asymmetry of glow peaks and their consistent analytical representation

The kinetic equation which describes many electronic as well as atomic or chemical reactions under the condition of a steadily linear raise of the temperature, is considered in a mathematically exact and straightforward way. Therefore, the equation has been transformed into a dimensionsless form, using with profit the maximum condition for the intensity peak. The two temperatures T₁ and T₂, corresponding to the half-height of the intensity peak, are found as unique polynomials of the small argument \(\bar y \equiv {{k\bar T} \mathord{\left/ {\vphantom {{k\bar T} E}} \right. \kern-0em} E}\) only ( \(\bar T\) =temperature of peak maximum). Thereupon, further combinations give half-widthδ, peak asymmetryA=δ₂/δ₁ or \(\tilde A = {{\bar C} \mathord{\left/ {\vphantom {{\bar C} {(1 - \bar C)}}} \right. \kern-0em} {(1 - \bar C)}}\) and the maximum of the intensity peakJ; they again all depend only on¯y. In some cases this dependence is weak, so that e.g. it is deduced that the half-width energy product divided by \(\bar T^2 \) is an invariant, different for every kinetic orderπ: $$\frac{{\delta \cdot E[eV]}}{{\bar T^2 }} = \left\{ {\begin{array}{*{20}c} {{1 \mathord{\left/ {\vphantom {1 {4998 K for monomolecular process}}} \right. \kern-\nulldelimiterspace} {4998 K for monomolecular process}}} \\ {{1 \mathord{\left/ {\vphantom {1 {3542 K for bimolecular process}}} \right. \kern-\nulldelimiterspace} {3542 K for bimolecular process}}} \\ {{1 \mathord{\left/ {\vphantom {1 {2872 K for trimolecular process}}} \right. \kern-\nulldelimiterspace} {2872 K for trimolecular process}}} \\ \end{array} } \right.$$ By means of these correlations, activation energy valuesE [eV] can be determined accurately to within 0.5 %, so that for most experiments the inaccuracy of theδ values becomes dominant and limiting. A special nomogram for the express estimation ofE from experimentally observedδ and \(\bar T\) is demonstrated.     

The effect of pressure on the formation of alkali metal borate ion pairs at 25°C

Pressure dependent UV-visible spectrophotometric measurements were used to determine \(\Delta \bar V^ * \) and \(\Delta \bar \kappa ^ * \) for the formation of alkali metal borate ion pairs. The association constant for each ion pair was measured at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. The pressure dependence of the apparent association constants, K _A (P)/K _A (1), have been fitted to $$[RT/(P - 1)]ln[K_A (P)]/[K_A (1)] = - \Delta \bar V^0 + \Delta \bar \kappa ^0 [(P - 1)/2]$$ to determine \(\Delta \bar V^0 and \Delta \bar \kappa ^0 \) . The \(\Delta \bar V^0 \) for the alkali metal borate ion pairs range from 5–9 cm³-mol^?1. The association constants were also measured as a function of ionic strength at 1 atm. Extrapolation to I=0 yielded K _A of 2.12, 0.66, 0.76 and 1.12 for [LiB(OH)₄], [KB(OH)₄], [RbB(OH)₄] and [CsB(OH)₄], respectively. The trend generally indicates less ion pairing and a smaller volume change for the ion pair formation as the size of the cation increases. The concept of localized hydrolysis is used to explain the trend observed in the equilibrium constant of the ion pair as the cation size is changed.     

Röntgenkleinwinkeluntersuchungen der strahleninduzierten Aggregation von Ribonuclease,Lactat-Dehydrogenase,Glycerinaldehyd-3-phosphat-Dehydrogenase und Serumalbumin. Ein Vergleich mit Malatsynthase

The X-ray induced aggregation of ribonuclease, lactate dehydrogenase (LDH), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and serum albumin in aqueous solution was monitored in situ by means of small-angle X-ray scattering. The time dependence of several molecular parameters viz. the apparent radius of gyration \(\tilde R\) , the maximum visible diameterD, the mean degree of aggregation \(\bar x\) , and the mean radius of gyration \(\bar R\) was used to compare the various proteins with each other and with malate synthase which has been studied previously (P. Zipper andH. Durchschlag, Radiat. and Environm. Biophys., 1980). Measurements carried out with ribonuclease,LDH and serum albumin in the absence of dithiothreitol (DTT) and withGAPDH in the presence of 0.2mM DTT established the following series for the rates of aggregation of the proteins under these conditions: ribonuclease>LDH>GAPDH>serum albumin. The rate of aggregation ofGAPDH was found to be of similar magnitude as that obtained for malate synthase under comparable experimental conditions (presence of 0.2mM DTT, similar X-ray intensity) in our previous study. Within six hours from the beginning of irradiation (i.e. about the time required for the exposure of one complete scattering curve under the conditions of our experiments) the following increases of \(\tilde R\) resulted: ribonuclease 9%,LDH 7%,GAPDH 4%, serum albumin<1%. Changes of \(\tilde R\) exceeding 1% are, of course, too high to be tolerated in conventional scattering experiments.     

Heat capacity and density of potassium iodide solutions in mixed N-methylpyrrolidone-water solvent at 298.15 K

The heat capacity and density of potassium iodide solutions in a mixed N-methylpyrrolidone (MP)-water solvent with a low content of the organic component are measured via calorimetry and densimetry at 298.15 K. Standard partial molal heat capacities \(\bar C_{p,2}^ \circ \) and volumes \(\bar V_2^ \circ \) of potassium iodide in MP-water mixtures are calculated. Standard heat capacities \(\bar C_{p,i}^ \circ \) and volumes \(\bar V_i^ \circ \) of potassium and iodide ions are determined. The character of the changes in heat capacity and volume are discussed on the basis of calculating additivity coefficients δ _c and δ _v upon the mixing of isomolal binary solutions KI-MP and KI-water, depending on the composition of the MP-H₂O mixture and the concentration of the electrolyte.     

Rendements de fission cumulatifs du252Cf

The cumulative yields of 28 isotopes have been measured in the spontaneous fission of²⁵²Cf. Measurements were made by Ge(Li) gamma-spectrometry. An average number of neutrons per fission \(\bar V:3.71\) was derived from the mass distribution. Using Terrell's method, and with the mass distribution before neutron emission, measured in an other laboratory and with our results, the mass-dependent variation of \(\bar V\) was also deduced.     

Fragmentation of doubly charged ammonia cations NH 3 ++ studied by the photoion-photoion coincidence (PIPICO) method

Doubly charged NH ₃ ⁺⁺ cations were produced by double photoionization of neutral ammonia molecules by using the synchrotron radiation from ACO as a photon source of variable energy in the 35–49 eV energy range. The fragmentation of NH ₃ ⁺⁺ was studied by the photoion-photoion coincidence (PIPICO) method. NH ₃ ⁺⁺ cations were produced in the \(\tilde X^1 \) A ₁ and \(\tilde B^1 \) electronic states of which the onset energies were measured at, respectively, 35.4±0.5 eV and 44.5±0.5 eV. It was shown that the NH ₃ ⁺⁺ ions, initially produced in their \(\tilde X^1 \) A ₁ state, rapidly dissociate (in less than 50 ns), into NH ₂ ⁺ + H⁺. Furthermore, the comparison with results obtained by other methods indicates that NH ₃ ⁺⁺ ions can either be long-lived (τ>10 µs) or slowly dissociating (1 µs<τ<10 µs) or rapidly dissociating (τ<50 ns), depending on their geometry and/or internal energy in their \(\tilde X^1 \) E A ₁ electronic state.     

The effective resonance energy\overline {E_r } as a parameter for the correction of resonance integrals in 1/E1+α epithermal neutron spectra; tabulation of\overline {E_r } -values for 96 isotopesfor 96 isotopes

The present paper shows that the effective resonance energy \(\overline {E_r } \) introduced by RYVES, is a useful parameter for the correction of resonance integrals in non-ideal epithermal neutron spectra, which can be approximated by a 1/E^1+α-flux distribution. The definition, the characteristics and the calculation of \(\overline {E_r } \) are discussed thoroughly. Tabulations are included, giving \(\overline {E_r } \) for 96 isotopes.     

A topological index for the totalπ-electron energy

A modified topological index \(\tilde Z_G \) is proposed to be defined as $$\tilde Z_G = \sum\limits_{k = 0}^{[N/2]} {( - 1)^k } a_{2k} $$ for characterising theπ-electronic system of a conjugated hydrocarbonG withN carbon atoms, wherea _2k is the coefficient of the characteristic polynomial ofG defined as $$P_G (X) = ( - 1)^N \det |A - XE| = \sum\limits_{k = 0}^N { a_k X^{N - k} } $$ with an adjacency matrixA and the unit matrixE. \(\tilde Z_G \) is identical toZ _G for a tree graph, or a chain hydrocarbon.Z _G increases with a (4n+2)-membered ring formation and decreases with a 4n-membered ring formation. The totalπ-electron energyE _π of the Hückel molecular orbital is shown to be related with \(\tilde Z_G \) asE _π =Cln \(\tilde Z_G \) . With this relation generalised and extended Hückel rules for predicting the stability of an arbitrary network are proved.     

Quadrupole moment of theNS 1/2-state of the hydrogen atom

The result of the quadrupole \(Q_{ns_{1/2} } \) calculation of the excitedns _1/2-state of the hydrogen atom is presented. It is shown that \(Q_{ns_{1/2} } \) turns out to be a factor (n ²+2)/3 larger than the ground-state quadrupole moment \(Q_{1s_{1/2} } \) .     

Doppelnebenklassen als Klassenbegriff und Nomenklaturprinzip für Isomere und ihre AbzÄhlung

The general principle of classifying molecules of a common gross formula according to “configurations” is founded on the combination of two abstractions among rigid molecular models with a common molecular frame, numbered places for ligands, and numbered ligands. It is shown that the various points of view, which can be taken for the classification are determined by two accordingly chosen subgroups \(\mathfrak{A}\) and \(\mathfrak{B}\) of a permutation group \(\mathfrak{S}\) , the configurations being defined by the double cosets of the product \(\mathfrak{A}\mathfrak{B}\) . Just as the irreducible representations of the symmetry group of an observable furnish the nomenclature for different types of eingenfunctions the double cosets here provide a nomenclature for the configurations. The special principle of classification is given by the choice of \(\mathfrak{A}\) , \(\mathfrak{B}\) and \(\mathfrak{S}\) . Thus, the enumeration of configuration leads to the generalised problem of enumerating double cosets. For this, three formulas are derived. In case of the special group \(\mathfrak{S} = \mathfrak{S}_n \) G. Pólya found a formula of enumeration which is shown to reduce to our formulas in the appendix.     

Frequencies of breathing vibrations of nearly spherical Ar clusters calculated by molecular dynamics

The breathing vibration of Ar _N cluster,N=13, 20, 25, 30 and 55, was investigated by use of the molecular dynamics method. The average distance \((\bar r)\) averaged over the positions of all Ar atoms with respect to the center of mass was calculated as a function of time and its frequency spectrum was derived by the Fourier transform analysis. The \(\bar r\) value was proved to be a good index of the breathing vibration in comparison with the exact breathing vibration of an Ar dense sphere. The vibrational frequency thus estimated,f _MD, was found to increase with the cluster sizen as expected.     

C(methyl)–H ⋅ ⋅ ⋅ π(aryl) Interaction Stabilizing Molecular Conformation. X-Ray Crystal Structure of an Inclusion Compound of a Nonprotic Host with Nitromethane Guest

In the cocrystal formation of a nonprotic polar (host) molecule (1) with nitromethane (guest) several weak, but directional, intermolecular interactions have vital importance. The endo conformation of the (N)-xylene group of the polycyclic succinimide-based host 1 is stabilized by a C_methyl $---$ H ??? π interaction [C ??? π /H ??? π distances are 3.554(7)/2.57 Å, the C $---$ H ??? π angle is 159^○], and the crystal packing is governed by dipole–dipole type interhost (C $ =$ )O ??? C( $ =$ O) connection [C ??? O $ =$ 3.000(5) Å and <C $ =$ O ??? C $ =$ 159.8(3)^○] in conjunction with possible C $---$ H ??? O interactions [with C ??? O distances ranging between 3.20 and 3.50 Å] involving the polar groups of both host and guest. Crystal data: 1 ??? nitromethane (1:1), C₂₆H₂₁O₂ N ? CH₃NO₂, M _w = 440.50, P2 ₁/n, a = 14.143(1), b = 7.973(1), c = 20.291(2) Å, β = 95.183(9)^○, Z = 4, D _c = 1.2840(2) g cm^?3, R = 0.055 for 1709 reflections.     

Statistical investigations of some element distributions in healthy and pathologically altered human colon mucosa

In this paper data are presented concerning the distribution of Cr, Sb, Sc, Fe, Co, and Zn in HCM, of patients with histopathologically and clinically verified findings: Healthy—N; Colitis Chronica-CCh; Colitis Ulcerosa-CU; Adenoma Tubulare-AT; Adenocarcinoma-ACa. The data are presented on the basis of the contents of elements (C_E parameter expressed in nkg/g of lyophilized HCM) obtained by INAA and calculated by computer programs, with statistical parameters (n, XBAR, XMIN-XMAX, R, V, SE and SDEV). The values of C_E parameters of elements found in all diagnostic groups (decreasing order) are also presented. The minimal \(\bar C_E \) parameters for all elements except Zn are found in diagnostic groups AT and ACa. The maximal differences of \(\bar C_E \) parameters in DS-decreasing orders are found for Sb (78.89%) and the minimal for Zn (18.89%).     

Determination of perturbed angular correlation parameter\overline {G_{22} } for111In in hydrochloric acid solutions by the sum peak methodfor111In in hydrochloric acid solutions by the sum peak method

Application of the sum peak method to indium solutions in hydrochloric acid has been studied. A calibration line to determine a PAC parameter \(\overline {G_{22} } \) has been adopted using two samples with known values of \(\overline {G_{22} } \) . The results show feasibility of the method because of its simplicity and of smaller amounts of radioactivity required in the measurement compared to the ordinary PAC method.     

An X-ray crystallographic study of the inclusion properties of additionally dimethylated members of the 2′-hydroxy-2,2,4-trimethylflavan host series

Consideration of the shape and hydrogen bonding pattern of anentire guest unit, in the known 2:1:2 complex of 2′-hydroxy-2,4,4,7,4′-pentamethylflavan (1) with 1,4-dioxan and water, has indicated a structurally compatible guest,trans-1,4-bis(hydroxymethyl)cyclohexane (3b) which is selectively clathrated from a mixture with itscis isomer (3a). The new complex is triclinic, space group,P \(\bar 1\) , witha=8.137(1),b=9.106(1),c=14.552(2) Å, α=93.56(1), β=94.08(1), γ=98.62(1)°, and two host and one guest molecule in the unit cell. A novel hydrogen bonded host-guest arrangement has also been found for host (1), involving ethanol and piperazine [triclinic, space groupP \(\bar 1\) , witha=8.438(1),b=10.252(1),c=14.052(1) Å, α=71.28(1), β=89.72(1), γ=83.88(1)δ]; while for the 1:1 ether adduct of (1) the triclinic unit cell, space groupP \(\bar 1\) , is approximately doubled in volume [a=8.309(2),b=10.546(3),c=26.664(6) Å, α=102.10(2), β=100.48(2), γ=81.04(2)°], there now being two crystallographically independent host-guest units involving ?OH·OEt₂ hydrogen bonds of length 2.71(1) Å and 2.77(1)Å. In the 2:1 complex of the isomeric host 2′-hydroxy-2,4,4,6,5′-pentamethylfavan (2) withN, N′-dimethylpiperazine (5) [triclinic space groupP \(\bar 1\) , witha=7.411(1),b=10.143(3),c=15.109(3)Å, α=98.73(2), β=88.30(1), γ=109.72(2)°] the centrosymmetric chair-shaped guest molecule is clamped by two axially oriented ?OH...N hydrogen bonds of length 2.759(3)Å.     

Electromagnetic structure of lighter antiprotonic atoms

The electric and magnetic fine structures of \(\bar p\) -atoms are tabulated up toZ=20. They are calculated perturbatively to second order in the Uehling potential, to first order in relativity and to all orders in recoil.     

Isotope effects in aqueous systems. VI. partial molal free energies in NaCl−H2O−D2O by freezing-point measurements. The heat of fusion of D2O

The freezing-point depressions of solutions of NaCl in normal and heavy water have been measured between 0.01 and 2m. Extrapolation of the isotope effect data to infinite dilution yields a new value for the heat of fusion of D₂O at its melting point (?1507±3 cal-mole^?1). The freezing-point data were employed to obtain osmotic coefficients at the feezing points of the solutions, which were corrected to rounded temperatures up to 40°C using the enthalpy data reported by Craft and Van Hook (previous paper). The data for H₂O solution are in quantitative agreement with well-established results. Those for the D₂O solvent establish the NaCl?D₂O system as an isopiestic reference. In contrast to the statements of earlier authors, examination of the isotope-effect data reveals a \(\surd \overline m\) dependence within experimental error.     

The first lonization constant of carbonic acid from 25 to 250°C and to 2000 bar

The apparent first ionization constant of carbonic acid has been determined by conductivity measurements and found to vary from 4.32×10^?7 at 25°C to 1.6×10^?8 at 250°C. The pressure effect to 2000 bar has been measured, and the ratio K_p/K₁ is 7.3 at 25°C and 19 at 250°C. The standard partial molar volume change for the ionization at 1 bar, \(\Delta \bar V_1^0\) , increases from ?27.6 cm³-mole^?1 at 25°C to ?88 cm³-mole^?1 at 250°C. The volume changes are smaller at higher pressures. A linear correlation between \(\Delta \bar V_1^0\) and the partial molar compressibility for the ionization reaction has been noted. A similar correlation exists between the partial molar entropy and volume changes for the reaction.     

Spectral variational principle for Green's functions

For a suitable approximation \(\tilde K\) (q, q′, τ) to the Dirac-Feynman Green's function of a quantummechanical system, the parameter \({\mathcal{L}\tilde K}\) is defined, where ?≡i?/?τ??. It is shown thatΔ≧0 andΔ→0 asK→K, the exact Green's function, thus providing a criterion on approximate Green's functions analogous in its role to the variational principle for wavefunctions. A second somewhat weaker criterion is also proposed, based on \(\Sigma \equiv \left[ {tr\tilde K*tr\mathcal{L}^2 \tilde K - |tr\mathcal{L}\tilde K|^2 } \right]_{\tau avg} \geqq 0\) . Recipes are given for projecting out continuum contributions toΔ or∑ and for analyzing for the discrete eigen-value spectrum.