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Thermodynamics of the Second Dissociation Constant and Standards for pH of 3-(NMorpholino) Propanesulfonic Acid (MOPS) Buffers from 5 to 55°C (1998)

Roy, Rabindra N. ; Mrad, Dawn R. ; Lord, P. A. ; [et al.]

Springer

Journal of solution chemistry 27 (1998), S. 73-87

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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

URL: http://dx.doi.org/10.1023/A:1022692629289

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Studien zur Verzweigung von Kettenmolekülen. X. Untersuchungen zur Kurzkettenverzweigung des HochdruckpolyethylensIX: Faserforsch. u. Textiltechnik/Z. Polymerforsch. 29 (1978) 521-525. (1979)

Schröder, E. ; Müller, G. ; Koch, W.

Weinheim : Wiley-Blackwell

Acta Polymerica 30 (1979), S. 557-562

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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.