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  • Polymer and Materials Science  (5)
  • enthalpy  (2)
  • resistance  (2)
  • 5'-O-demethyl-8-O-methyl-dioncophylline A  (1)
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  • 1
    ISSN: 1572-8927
    Keywords: Deuterium chloride ; deuterium oxide ; electrochemical cell ; emf ; enthalpy ; entropy ; free energy ; heat capacity ; isotope effect ; standard potential ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The themodynamic properties of solutions of deuterium chloride (DCl) in deuterium oxide (D2O) have been determined from emf measurements of the electrochemical cell without transference from 5 to 50°C, and from 0.002 to 1.0 mol-kg−1. The standard potential of the silver/silver chloride electrode relative to the platinum/deuterium electrode has been determined. An equation for the Gibbs energy as a function of temperature has been derived from which the enthalpy, entropy, and heat capacity have been computed. Equations for the activity coefficient and the osmotic coefficient of DCl in D2O have been developed. The excess Gibbs energy of the solution and the excess partial molar free energy as a function of temperature have been calculated, from which the other excess thermodynamic properties have been computed. The values for the heat capacity and the apparent molar heat capacity have been compared with calorimetric data in the literature. The relative partial molar enthalpy has been calculated. The solvent isotope effect on the excess thermodynamic functions is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8927
    Keywords: Aqueous solution ; cell constant ; conductance ; electrolytic conductivity ; potassium chloride ; primary ; resistance ; resistivity, secondary, standards, and temperature scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Measurements of aqueous electrolytic conductance are performed routinely in a variety of disciplines and industries. Conductivity is a measure of the ionic content in solution and thus has applications in pharmaceuticals, power plants, rainwater, lake surveys, and oceanography, to name a few. A thorough review of the measurement of and standards for aqueous electrolytic conductance is herein presented. At present, the most precise and accurate standards have been set forth by the International Organization of Legal Metrology (OIML), and have been adopted by most other standards organizations. However, the uncertainty assigned to these standards, especially the secondary standards, is somewhat larger than would be expected from the physical aspects of the measurement. Several changes in the units and measurement scales, including temperature, volume, molar mass, resistance, and concentration obfuscate the accuracy of these standards. In addition to the review, research is proposed, using a conductance cell with variable length, to establish new standards for aqueous electrolytic conductance.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 12 (1985), S. 105-123 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Certain polymerization reactions show the formation of medium molecular weights at the beginning of the reaction, although they can be considered to be polycondensations. The principle of equal reactivity of the end groups is not given in this case. Intermediates more reactive than the monomer are formed during the reaction. Poly(oxy-2,6-dimethyl-l,4-phenylene), poly(l,4-phenylene sulfide) and poly(l,4-phenylene) are examples of this type of reaction. The formation of radical ions in these reactions is discussed and they are compared to Bunnett's SRN1-reactions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 17 (1991), S. 947-950 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Auger spectra from highly samples (Al2O3, Si3N4) are collected in a gaseous environment. It is demonstrated that the build-up of negative surface charge can be reduced considerably under suitable conditions. It is proposed that the decharging of the surface is initiated by Auger neutralization of the ions formed in the gaseous environment in collisions with the primary keV electrons.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The short chain branching in low density polyethylene obtained under various conditions were determined by γ-irradiation followed by gaschromatography of the gaseous scission products. The pressure and temperature of polymerization were found to affect the kind and number of branchings. The branching structure and reaction parameters are related and discussed on a kinetic concept.
    Notes: Die Kurzkettenverzweigung von unter verschiedenen Bedingungen synthetisierten Hochdruckpolyethylenen wurde mit Hilfe der γ-Bestrahlung und nachfolgender gaschromatographischer Analyse der Spaltgase bestimmt. Es wurde experimentell belegt, daß Reaktionsdruck und Polymerisationstemperatur Art und Anzahl der Seitenzweige beeinflussen. Verzweigungsstruktur und Reaktionsparameter werden zueinander in Beziehung gesetzt und auf der Grundlage kinetischer Überlegungen diskutiert.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-8927
    Keywords: Cell constant ; conductance ; demal ; electrolytic conductivity ; potassium chloride ; primary standards ; resistance ; specific conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An absolute determination of aqueous electrolytic conductivity has been made for primary standards 0.01D and 0.1D (demal) potassium chloride solutions over the temperature range of 0 to 50°C in 5 degree intervals. A cell with a removable center section of accurately known length and area was used for the measurements. Values were adjusted to be in conformity with the ITS-90 temperature scale. The overall uncertainty over the entire temperature range is estimated to be 0.03%. Values at 25°C for 0.01D and 0.1D KCl solutions are 0.0014086 and 0.012852 S-cm−1, respectively.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-8927
    Keywords: Dissociation constant ; buffers ; NaMOPS ; temperature dependence ; emf ; Gibbs energy ; enthalpy ; entropy ; heat capacity ; zwitterion ; liquid junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The second dissociation constant pK2 of 3-(N-morpholino)propanesulfonic acid (MOPS) has been determined at eight temperatures from 5 to 55°C by measurements of the emf of cells without liquid junction, utilizing hydrogen electrodes and silver–silver chloride electrodes. The pK2 has a value of 7.18 ± 0.001 at 25°C and 7.044 ± 0.002 at 37°C. The thermodynamic quantities ΔG°, ΔH°, ΔS°, and ΔC p o have been derived from the temperature coefficients of the pK 2. This buffer at ionic strength I = 0.16 mol-kg−1 close to that of blood serum, has been recommended as a useful secondary pH standard for measurements of physiological fluids. Five buffer solutions with the following compositions were prepared: (a) equimolal mixture of MOPS (0.05 mol-kg−1) + NaMOPS, (0.05 mol-kg−1); (b( MOPS (0.05 mol-kg−1) + NaMOPS (0.05 mol-kg−1) + NaCl (0.05 mol-kg−1); (c) MOPS (0.05 mol-kg−1) + NaMOPS (0.05 mol-kg−1); + NaCl (0.11mol-kg−1); (d) MOPS (0.08 mol-kg−1) + NaMOPS (0.08 mol-kg−1); and (e)MOPS (0.08 mol-kg−1) + NaMOPS (0.08 mol-kg−1) + NaCl (0.08 mol-kg−1).The pH values obtained by using the pH meter + glass electrode assembly are compared with those measured from a flow–junction calomel cell saturated with KCl (cell B), as well as those obtained from cell (A) without liquid junction at 25 and 37°C. The conventional values of the liquid junction potentials E j have been obtained at 25 and 37°C for the physiological phosphate reference solution as well as for the MOPS buffers (d) and (e) mentioned above.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method using sodium amalgam electrodes has been developed to study the effect of protein on activity measurements and residual liquid junction potential of sodium in protein-containing solutions. It was tested for reliability by application to aqueous sodium chloride solutions before it was applied to protein-containing solutions. The experimentally determined activity coefficients are in good agreement with the activity coefficients for aqueous sodium chloride solutions reported in literature. Therefore, we used this method to measure the activity of NaCl solutions containing varying concentrations of bovine serum albumin (BSA). The electrode slope of the electrode responses in a protein-containing medium does not differ from that of pure aqueous solutions. A functional relationship has been established between the concentration of protein and the percent bias in the measurements. Measurements of electromotive force made in protein-containing solutions do not show any evidence of protein effect on liquid junction potential.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Analytical Chemistry used for developing new materials. The development of new materials constantly confronts the analyst with difficult new problems. Of particular importance for this work would be all methods permitting to lay bare the phase interface and to study their structure and perturbations of this structure. The analyst has to solve these problems in close contact with the technologists specializing in this modern technique.
    Notes: Die Entwicklung neuer Werkstoffe stellt den Analytiker vor immer neue diffizile Aufgaben. Insbesondere dürften alle Verfahren, mit denen es gelingt, Phasengrenzflächen freizulegen und ihren Aufbau sowie Störungen in diesem Aufbau zu studieren, für diese Aufgaben von großer Bedeutung sein. Der Analytiker muß diese Aufgaben in engster Fühlung mit den Technologen, die sich dieser modernen Entwicklung verschrieben haben, lösen.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0031-9422
    Keywords: 5'-O-demethyl-8-O-methyl-7-epi-dioncophylline A ; 5'-O-demethyl-8-O-methyl-dioncophylline A ; Dioncophyllaceae ; Triphyophyllum peltatum ; atropisomerism. ; biaryls ; naphthylisoquinoline alkaloids ; stem bark
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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