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contrasts with vaporization which, although avoids first pass metabolism, and is a more accepted and easier route of administration, induces a rapid onset of effects through a much more complex drug delivery and finally makes it challenging to control dose

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Abstract  

Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An addition of a small amount of hydrazine hydrate N2H4H2O was proposed to increase the thermal stability of UDMH. The mixture where the mass ratio (CH3)2NNH2/N2H4H2O is equals to 75/25, is called UH25. These propelling agents are unstable when they are heated and the optimisation of burning conditions requires a good knowledge of their vaporisation and of their thermal decomposition kinetics.

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Abstract  

A method was devised to evaluate latent heats of vaporization from quasi-isothermal isobaric analysis data. The procedure requires the recording of at least two diagrams: one for the investigated liquid, and the other for a standard liquid with a known latent heat of vaporization. Use of the method to determine the heats of vaporization of some alcohols, with water as standard liquid, led to results close to those previously reported in the literature. The main advantage of the procedure consists in the fact that it requires only small amounts of sample (5–10 mg).

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Summary  

The electrochemical reduction of uranium oxide in the treatment of spent nuclear fuel requires a characterization of the LiCl-Li2O salt used as a reaction medium. Physical properties, melting and vaporization are important for the application of the salt and thus they have been investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG), respectively. Experimental data suggest LiCl and Li2O compound formations, leading to a melting point depression of the LiCl and a co-vaporization of the LiCl-Li2O salt.

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Abstract  

The vaporization of samples of different chemical and phase compositions in the systems CsCl-LnCl3 (Ln=Ce, Nd) was investigated in the temperature range between 850 and 1050 K by the use of Knudsen effusion mass spectrometry. The gaseous species CsCl, Cs2Cl2, LnCl3, Ln2Cl6 and CsLnCl4 were identified in the vapour and their partial pressures were determined. The thermodynamic activities of CsCl, and LnCl3 and the free enthalpies of formation for the phases Cs3LnCl6(s) were determined at 950 K in the two phase fields {liquid+Cs3LnCl6(s)}. The correlations between the condensed phase equilibria and the partial pressures of the vapour components at the phase boundaries are discussed and illustrated with the present experimental data.

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Abstract  

The main purpose of this paper is to prove the applicability of the mechanism of congruent dissociative vaporization (CDV) to the solid-state decomposition kinetics through the comparison of the fundamental theoretical relationship E i/E e=(a+b)/a resulted from this mechanism with experiment. It has been shown that the ratios of E i and E e parameters of the Arrhenius equation measured in the isobaric and equimolar modes (in the presence and absence of H2O vapour) for 22 reactants with the general formula aSalt⋅bH2O or aOxide⋅bH2O are in agreement with the values of (a+b)/a. The relative standard deviation is only 17% and the correlation coefficient is close to 0.99. A probability of accidental correlation for all set of the E parameters taken from the literature is lower than 4⋅10–16 . This strongly supports the validity of the CDV mechanism. The problem of stability of polyatomic molecules of inorganic salts in the gaseous state, which are the primary decomposition products of crystalline hydrates, was also discussed on the basis of recent mass spectroscopy studies. It was concluded that any doubts in the applicability of the CDV mechanism as a general mechanism of solid-state decomposition reactions are unsound.

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Abstract  

The standard sublimation enthalpies of (2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline were determined by isothermal thermogravimetry using the Langmuir equation and by non-isothermal differential scanning calorimetry for comparison. The used procedure was previously tested using three reference compounds: benzoic acid, succinic acid and salicylic acid. The results compared to those reported in literature show an excellent agreement for two of the three compounds while the third agrees quite well. For (2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline, the extrapolation of data at 298.15 K were obtained, respectively: Δsub H(298 K)={(1064) and (1014)} kJ mol–1. From Clausius Clapeyron equation obtained after the determination of the vaporization constant α′, the following standard sublimation entropies for (2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline equal to Δsub S(298 K)=(251 and 237) J K–1 mol–1, respectively, were derived, with an error of 4 J K–1 mol–1 equal for the studied herbicides.

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Journal of Thermal Analysis and Calorimetry
Authors: Xian'e Cia, Daichun Du, Youming Jin, and Yixiang Qian

Abstract  

N(C5F11)3 (Fluorint FC-70) has been chosen as the test material to compare the chemicophysical data obtained by static-sample and DSC methods. The normal boiling point, the molar enthalpy of vaporization, and the constants of the Antoine equation of fluorint FC-70 are reported. DSC can be developed into a simple and rapid routine instrument to determine the enthalpy of vaporization as well as the boiling point of liquid, particularly at relative high temperature.

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A miniaturized effusion cell adapted to a Sorption LKB microcalorimeter has been designed, built and tested. Vaporization is performed isothermally into a vacuum through a small orifice permitting a vapour pressure very close to the equilibrium values. The cell has been tested by measuring the enthalpies of vaporization at 298.15 K of reference liquid compounds (water, benzene, propanol-1, propanol-2) with a reproducibility better than 1%. Enthalpies of vaporization of butanol-1 and deuterated water have also been determined.

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Abstract  

Temperature dependences of solubility, saturated vapour pressure and crystal heat capacity of [4-(Benzyloxy)phenyl]acetic acid were determined. The solubility of this compound was investigated in n-hexane, buffered water solutions with pH 2.0 and 7.4 and n-octanol. The enthalpy of sublimation and vaporization as well as the fusion temperature were determined. Solvation and solubility processes have been analyzed. The thermodynamics of transfer processes from one buffer to another (protonation process), from buffers to 1-octanol (partitioning process), and from n-hexane to the applied solvents (specific interaction) have been calculated and compared to those of other NSAIDs. The relevant shares of specific and non-specific interactions in the process of solvation have been investigated and discussed.

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