Automated, small sample-size adiabatic calorimeter

Oort, Michiel J. M. Van; White, Mary Anne

doi:10.1063/1.1139445

Cited by 27 publications

(10 citation statements)

References 22 publications

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“…19 Briefly, the apparatus consisted of a sample cell ͑ϳ5 mL͒ with a centrally located thermometer well containing a platinum resistance thermometer. The cell was surrounded by heater wire and suspended inside an adiabatic shield in a cryostat.…”

Section: Sample Preparation and Experimental Methodsmentioning

confidence: 99%

Why is there no low-temperature phase transition in NaOH?

Bessonette

White

1999

The Journal of Chemical Physics

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Articles you may be interested inDeuteration effect on tricritical phase transition of triglycine selenate: Calorimetric and dielectric measurements analyzed in the framework of Landau theory Although NaOH and NaOD exhibit parallel polymorphism at high temperatures, NaOD exhibits a low-temperature phase transition to a hydrogen-bonded antiferroelectric phase and no comparable transition has been found in NaOH. Measurements of NaOH by dielectric relaxation and adiabatic calorimetry were undertaken to determine if proton disorder becomes frozen in NaOH at low temperatures. No evidence for relaxation in NaOH was found from calorimetry or dielectric measurements. A comparison of the low-temperature heat capacities of NaOH and NaOD showed that NaOH has excess heat capacity, likely due to the existence of tunneling levels, and this was satisfactorily fit to a two-level Schottky anomaly. Thus, hydrogen-atom ordering in NaOH appears to take place through a more gradual process at low temperatures, rather than a low-temperature phase transition as in NaOD. The difference in the behaviour of NaOH and NaOD likely is associated with oxygen-oxygen distances that are slightly longer in NaOH than in NaOD, owing to the different nature of higher-temperature dynamical disorder ͑classical double-well potential for OD Ϫ and tunneling for OH Ϫ ͒.

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Section: Sample Preparation and Experimental Methodsmentioning

confidence: 99%

Why is there no low-temperature phase transition in NaOH?

Bessonette

White

1999

The Journal of Chemical Physics

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“…The calorimeter, which is described in detail elsewhere (14), is known to have an accuracy of k 0.5% from our measurement of the heat capacity of Calorimetry Conference (NBS-49) benzoic acid. The temperature (resistance of the Pt thermometer) and heat input were measured with a Hewlett-Packard 3456A digital multimeter, interfaced with a Hewlett-Packard HP87A personal computer (14).…”

Section: Methodsmentioning

confidence: 99%

The thermodynamics of orientational disorder in a molecular solid: (CH₃)₃CCHO

White¹,

Perrott²

1988

Can. J. Chem.

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This paper is dedicated to Professor James A. Morrison MARY ANNE WHITE and ALLYSON PERROTT. Can J. Chem. 66, 729 (1988) The heat capacity of tert-butylaldehyde, (CH3)3CCH0, has been measured as a function of temperature from 29 to 298 K, to investigate solid-state polymorphism. There are two solid-solid phase transitions in this material, T,, = 158.5 and 183.9 K, AS,, = 0.402R and 3.153R respectively. The thermodynamic parameters for the transitions are consistent with mechanisms proposed on the basis of recent nuclear magnetic resonance investigations of this material.MARY ANNE WHITE et ALLYSON PERROTT. Can J. Chem. 66, 729 (1988) Afin d'ttudier le polymorphisme a l'ttat solide, on a mesurt la capacitt calorifique du tert-butylaldthyde, (CH3)3CCH0, en fonction de la temptrature de 29 a 298 K. Avec ce produit, on a observt deux transitions de phase solide-solide, T,, = 158,5 et 183,9 K, AS,, = 0,402R et 3,153R. Les paramktres thermodynamiques pour les transitions sont en accord avec les mtcanismes proposts en se basant sur des etudes rtcentes en resonance magnttique nucltaire de ce compost.[Traduit par la revue]

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“…The heat capacities of CsHS and CsDS ͑sample masses 4.570 and 4.552 g, respectively͒ were determined from about Tϭ30 K to Tϭ300 K by adiabatic heat pulse calorimetry, as described in detail elsewhere. 32 Briefly, the sample, in a sealed calorimeter, was increased in temperature by quantified Joule heating, while adiabatic conditions were maintained. The temperature was monitored with a platinum resistance thermometer, and the temperatures before and after application of the heat pulse were determined.…”

Section: Calorimetric Investigationsmentioning

confidence: 99%

Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray diffraction, calorimetry and proton NMR investigations

Haarmann

Jacobs

Kockelmann

et al. 2002

The Journal of Chemical Physics

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Protonated and deuterated samples of the hydrogensulfide of cesium were studied by high-resolution neutron powder diffraction, calorimetry and proton NMR investigations in a wide temperature range. Primarily due to reorientational disorder of the anions, three modifications of the title compounds are known: an ordered low-temperature modification- LTM (tetragonal, I4/m, Z=8), a dynamically disordered middle- temperature modification-MTM (tetragonal, P4/mbm, Z=2), and a high-temperature modification-HTM (cubic, Pm (3) over barm, Z=1). The LTMreversible arrowMTM phase transition is continuous. Its order parameter, related to an order/disorder and to a displacive part of the phase transition, coupled bilinearly, follows a critical law. The critical temperature T- C=123.2+/-0.5 K determined by neutron diffraction of CsDS is in good agreement with T-C=121+/-2 K obtained by calorimetric investigations. For the protonated title compound a shift to T- C=129+/-2 K was observed by calorimetric measurements. The entropy change of this transition is (0.24+/-0.04) R and (0.27+/-0.04) R for CsHS and CsDS, respectively. The MTMreversible arrowHTM phase transition is clearly of first order. The transition temperatures of CsHS and CsDS are T=207.9+/-0.3 K and T=213.6+/-0.3 K with entropy changes of (0.86+/-0.01) R and (0.81+/-0.01) R, respectively. Second moments (M-2) of the proton NMR absorption signal of MTM and HTM are in reasonable agreement with M-2 calculated for the known crystal structures. A minimum in spin-lattice relaxation times (T-1) in the MTM could not be assigned by dipolar coupling to a two-site 180degrees reorientation of the anions, a model of motion presumed by the knowledge of the crystal structure. The activation enthalpies determined by fits of T-1 presuming a thermal activated process are in the order of molecular reorientations (E-a=13.5+/-0.5 kJ mol(-1) for the MTM and E-a=9.3+/-0.3 kJ mol(-1) for the HTM). In the HTM at T>330 K translational motion of the cations determines T-1 (E- a=13.8+/-0.4 kJ mol(-1)). (C) 2002 American Institute of Physics

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Automated, small sample-size adiabatic calorimeter

Cited by 27 publications

References 22 publications

Why is there no low-temperature phase transition in NaOH?

Why is there no low-temperature phase transition in NaOH?

The thermodynamics of orientational disorder in a molecular solid: (CH₃)₃CCHO

Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray diffraction, calorimetry and proton NMR investigations

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Automated, small sample-size adiabatic calorimeter

Cited by 27 publications

References 22 publications

Why is there no low-temperature phase transition in NaOH?

Why is there no low-temperature phase transition in NaOH?

The thermodynamics of orientational disorder in a molecular solid: (CH3)3CCHO

Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray diffraction, calorimetry and proton NMR investigations

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Product

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The thermodynamics of orientational disorder in a molecular solid: (CH₃)₃CCHO