The Heat Capacity and Entropy, Heats of Transition, Fusion and Vaporization and the Vapor Pressures of Cyclohexane. The Vibrational Frequencies of Alicyclic Ring Systems<sup>1</sup>

Aston, J. G.; Szasz, George; Fink, H. L.

doi:10.1021/ja01246a034

Cited by 179 publications

(61 citation statements)

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“…temperature at the gold surface and the PT-100 temperature has been tested by observation of the infrared spectrum of a well defined phase transition of cyclohexane which occurs at 189.06 K (Aston et al, 1943). The measured temperature of the phase transition agrees within 0.005 K with the value from literature.…”

Section: Appendix a Experimentalmentioning

confidence: 63%

Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

et al. 2006

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Abstract.We have analyzed mid-infrared limb-emission measurements of polar stratospheric clouds (PSCs) by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) during the Antarctic winter 2003 with respect to PSC composition. Coincident Lidar observations from McMurdo were used for comparison with PSC types 1a, 1b and 2. Application of new refractive index data of β-NAT have allowed to accurately simulate the prominent spectral band at 820 cm −1 observed by MIPAS at the location where the Lidar instrument observed type 1a PSCs. Broadband spectral fits covering the range from 780 to 960 cm −1 and from 1220 to 1490 cm −1 showed best agreement with the MIPAS measurements when spectroscopic data of NAT were used to simulate the MIPAS spectra. MIPAS measurements collocated with Lidar observations of Type 1b and Type 2 PSCs could only be reproduced by assuming a composition of supercooled ternary H 2 SO 4 /HNO 3 /H 2 O solution (STS) and of ice, respectively. Particle radius and number density profiles derived from MIPAS were generally consistent with the Lidar observations. Only in the case of ice clouds, PSC volumes are partly underestimated by MIPAS due to large cloud optical thickness in the limb-direction. A comparison of MIPAS cloud composition and Lidar PSC-type determination based on all available MIPAS-Lidar coincident measurements revealed good agreement between PSC-types 1a, 1b and 2, and NAT, STS and ice, respectively. We could not find spectroscopic evidence for the presence of nitric acid dihydrate (NAD) from MIPAS observations of PSCs over Antarctica in 2003.

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Section: Appendix a Experimentalmentioning

confidence: 63%

Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

et al. 2006

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“…The cell parameters are only slightly shortened at the lowest temperature and the extinction rules are the same. Thermodynamics does not detect any transition below 186°K (Aston et al, 1943;Ruehrwein & Huffmann, 1943). N.m.r.…”

Section: Structure Determination and Refinementmentioning

confidence: 81%

Crystal structure of cyclohexane I and II

Kahn¹,

Fourme²,

André³

et al. 1973

Acta Crystallogr Sect B

178

108

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Cyclohexane C6H12 (m.p. 279.8 °K) undergoes an isothermal transition at 186 °K. The so-called phase I is stable between 279.8 and 186°K, phase II below 186°K. Starting from a single crystal I grown by a zone melting technique at 187 °K, suitable single crystals II were obtained through a careful control of the phase transformation and annealing at 185 °K for two days. X-ray diffraction data have been collected at 195 and 115 °K by the low-temperature precession technique. At 115 °K, crystal data are: monoclinic cell, a= 11.23 (2), b = 6.44 (2), c= 8.20 (2) A, fl= 108.83 (17) °, Z= 4; space group Cc or C2/c (the analysis confirmed the centrosymmetric group). The crystal and molecular structures were refined to an R index of 0.061 ; the 'chair'-shaped molecule departs slightly but significantly from Dan symmetry. The rigid-body model is a good approximation for the thermal motion. At 195 °K, crystal data for the plastic phase I are: cubic cell, a = 8.61 (2)/~, Z= 4, space group Fm3m. Using the molecular shape previously found, two types of orientational disorder have been investigated: isotropic reorientations of the molecules about their centre of gravity (Pauling-Fowler model) and step reorientations between 24 equivalent positions (Frenkel model). In this case, the packing was found by a Monte-Carlo method coupled with a rigidgroup least-squares refinement. The Frenkel model gives a better agreement with experiment. A tentative interpretation of the transformation is given. The same general procedure can probably be applied to other plastic crystals.

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“…v é a densidade de ligações cruzadas; x é o parâmetro de interação borracha-solvente (NR-ciclohexano 0,399) [14] . v 1 é o volume molar do ciclohexano (108,75 cm 3 .mol -1 ).…”

Section: Ensaio De Inchamentounclassified

Influência do método de vulcanização nas propriedades mecânicas e na densidade de ligações cruzadas da borracha natural

et al. 2016

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ResumoA vulcanização é um importante fator que determina as propriedades mecânicas da borracha, mas a influência do método de vulcanização nas propriedades mecânicas do material, ainda é um assunto pouco explorado na literatura. Neste artigo, uma formulação à base de poli-cis-isopreno ou borracha natural (NR), denominada NR4010-A, foi vulcanizada em prensa e autoclave, com o objetivo de avaliar a influência do método de vulcanização na formação das ligações cruzadas e, consequentemente, nas propriedades mecânicas do material. Amostras do material vulcanizado, pelos dois métodos, foram caracterizadas por meio de análise reométrica, ensaio de inchamento e testes mecânicos, onde foi avaliada a resistência ao rasgo e à tração. Os resultados mostraram que para essa formulação, nas mesmas condições de temperatura, o método de vulcanização por autoclave se mostrou mais eficiente em relação às propriedades estudadas. Palavras-chave: ligações cruzadas, NR, propriedades mecânicas, vulcanização. AbstractVulcanization is an important factor on rubber mechanical properties determination. The influence of vulcanization method on mechanical properties is still an ongoing issue. Thus, a composition based in natural rubber (NR), named NR4010-A, was vulcanized by autoclave and press, on purpose to evaluated the vulcanization method influence on crosslink formation and thereafter on the mechanical properties of this material. Samples of vulcanized material in both conditions were characterized through swelling, rheometer tests, tear strength, strain strength and hardness. The mechanical properties studied and crosslink density were increased when the material was vulcanized by autoclave. Therefore, autoclave vulcanization method showed be more effective than press at the same conditions of temperature.

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The Heat Capacity and Entropy, Heats of Transition, Fusion and Vaporization and the Vapor Pressures of Cyclohexane. The Vibrational Frequencies of Alicyclic Ring Systems¹

Cited by 179 publications

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Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

Crystal structure of cyclohexane I and II

Influência do método de vulcanização nas propriedades mecânicas e na densidade de ligações cruzadas da borracha natural

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The Heat Capacity and Entropy, Heats of Transition, Fusion and Vaporization and the Vapor Pressures of Cyclohexane. The Vibrational Frequencies of Alicyclic Ring Systems1

Cited by 179 publications

References 0 publications

Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

Crystal structure of cyclohexane I and II

Influência do método de vulcanização nas propriedades mecânicas e na densidade de ligações cruzadas da borracha natural

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The Heat Capacity and Entropy, Heats of Transition, Fusion and Vaporization and the Vapor Pressures of Cyclohexane. The Vibrational Frequencies of Alicyclic Ring Systems¹