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21.
Vaporisation et dissociation thermique des sulfures de phosphore P4S3, P4S7 et P4S10 a l'etat gazeux
J. Bouix R. Hillel H. Vincent Y. Monteil 《Journal of Thermal Analysis and Calorimetry》1977,12(3):371-382
Résumé Nous avons montré par spectrométrie Raman à chaud et mesure des tensions de vapeur que P4S3 se vaporise de façon congruente tandis que P4S7 et P4S10 se dissocient dès le début de leur vaporisation. P4S7 donne réversiblement P4S3 et soufre. P4S10 se dissocie irréversiblement en P4S7 et soufre. A l'état de vapeur non saturante, P4S3 se dissocie au-dessus de 600° avec formation de phosphore, de soufre et d'autres espèces non identifiées.Nous avons mesuré expérimentalement la capacité calorifique de P4S3 liquide, calculé celle de P4S3 gazeux et son entropie standard. Nous avons aussi estimé l'enthalpie standard de vaporisation de P4S3 à l'aide des mesures des tensions de vapeur saturante. Nous en avons déduit l'entropie standard de P4S3 liquide et son point d'ébullition.
Nous remercions Monsieur Letoffe du laboratoire du Professeur J. Bousquet, INSA de Lyon, 20 Avenue Albert Einstein 401, 69621 Villeurbanne, qui a r6alis6 pour nous les déterminations expérimentales des capacités calorifiques de P4S8 liquide. 相似文献
It is shown by Raman spectroscopy at high temperature and by vapor tensimetric measurements that the vaporisation of P4S3 is congruent, whereas P4S7 and P4S10 dissociate at the beginning of vaporisation. P4S7 gives P4S3 and sulfur reversibly. The dissociation of P4S10 into P4S7 and sulfur is irreversible. Above 600°, in non-saturated vapour the dissociation of P4S3 gives phosphorus, sulfur and some unidentified gaseous species. The heat capacity of liquid P4S3 has been measured. That of gaseous P4S3 and its standard entropy have been calculated. The vaporisation standard enthalpy of P4S3 has been estimated from the experimental results on the saturated vapour pressures. The standard entropy of liquid P4S3 and its boiling point have been derived from these data.
Zusammenfassung Mittels Raman-Spektrometrie bei erhöhter Temperatur und durch Messung der Dampfdrucke wurde festgestellt, daß sich P4S3 verflüchtigt, während P4S7 und P4S10 mit Beginn der Verflüchtigung dissoziieren. P4S7 ergibt reversibel P4S3 und Schwefel. Im Zustand ungesättigten Dampfes dissoziiert P4S3 oberhalb von 600° unter Bildung von Phosphor, Schwefel und anderer nicht identifizierter Substanzen.Die Wärmekapazität von flüssigem P4S3 wurde gemessen, während die vom gasförmigem P4S3 sowie seine Standard-Entropie berechnet wurden. Die Standard-Enthalpie der Verflüchtigung des P4S3 wurde durch Messungen der Sättigungs-Dampfdrucke ermittelt. Daraus wurden die Standard-Entropie des flüssigen P4S3 sowie sein Siedepunkt berechnet.
- - , P4S3 , P4S7 P4S10 . P4S7 P4S3 , P4S10 P4S7 . 600° P4S3 , . P4S3, P4S3 . P4S3. P4S3 .
Nous remercions Monsieur Letoffe du laboratoire du Professeur J. Bousquet, INSA de Lyon, 20 Avenue Albert Einstein 401, 69621 Villeurbanne, qui a r6alis6 pour nous les déterminations expérimentales des capacités calorifiques de P4S8 liquide. 相似文献
22.
J. S. Vincent A. H. Dougan D. L. Lyster J. W. Blue 《Journal of Radioanalytical and Nuclear Chemistry》1981,65(1-2):17-29
A facility for the continuous production of iodine-123 by spallation of elemental caesium by 482 MeV protons has been in operation
at a TRIUMF beam dump for about 2 years. Radioxenon from the target is efficiently trapped on alumina which is subsequently
used to remove the121Te decay product. The yield is 100 mCi/h from a 20 gm/cm2 target at 10 μA. Impurities are125I<2% and121Te<0.2% at 27 hours after end of production. The123I consists mainly of iodide along with significant iodate impurity. The product is used extensively in Canadian clinics for
thyroid analyses and for labelling radiopharmaceuticals. 相似文献
23.
Dugas V Broutin J Souteyrand E 《Langmuir : the ACS journal of surfaces and colloids》2005,21(20):9130-9136
DNA chips are potentially powerful technologies for genotyping and gene expression profiling that rely on comparative analyses of up to thousands of "spots of analysis" on a glass support. The spot quality throughout the support influences spot-to-spot variations within an array and the repeatability of data across experiments. For glass slide DNA microarrays, droplets of DNA solution are deposited on functionalized glass slides and left to react through complete evaporation of the droplet. On hydrophobic flat surfaces, different modes of droplet evaporation can be attained. Under atmospheric pressure, water droplets tend to evaporate under two main regimes. Initially, the droplet flattens with a constant contact area, and then the droplet shrinks at a constant contact angle. As a result, the diameter and morphology of thousands of spots on microarrays are not uniform. This leads to poor and unreliable data processing results. In this work, we report the evaporation of an aqueous solution under a constant contact area mode. Evaporation under reduced pressure and the effect of reagent additives to the solution have been investigated. Video microscopy and digital image analysis techniques were applied to monitor the evaporation of the droplets. A mixture of surfactants was developed to maintain a constant area regime during evaporation and to form homogeneous spots. The control of some physicochemical properties (wetting, evaporation rate) of the droplet allows the formation of well-controlled spots compatible with DNA grafting. The influence of surfactant molecules on the mechanisms of evaporation is also discussed. 相似文献
24.
Zampella G Fantucci P Pecoraro VL De Gioia L 《Journal of the American Chemical Society》2005,127(3):953-960
Density functional theory has been used to investigate structural, electronic and reactivity properties of complexes related to the peroxo forms of vanadium haloperoxidases (VHPO). In particular, the reactivity of the cofactor as a function of protonation state and environment, which are two factors thought to be crucial in modulating the activity of the enzyme, has been examined. In full agreement with experimental data, results highlight the role of protonation in the activation of the peroxo-vanadium complexes and show that the oxo-transfer step involves the unprotonated axial peroxo oxygen atom, which is easily accessible to substrates in the peroxo form of the enzyme. The role of Lys353, which in the X-ray structure of the peroxide-bound form of vanadium chloroperoxidase is hydrogen bonded to the equatorial oxygen atom of the peroxo group, has been also explored. It is concluded that Lys353 can play a role similar to a H+ in the activation of the peroxo form of the cofactor. 相似文献
25.
Brahim Lakhrissi Mohamed Massoui El Mokhtar Essassi Vincent Lequart Nicolas Joly Patrick Martin Grard Goethals 《Journal of heterocyclic chemistry》2004,41(6):1011-1014
Reaction of 1,5‐benzodiazepin‐2,4‐dione with 3‐O‐substituted‐5,6‐anhydro‐1,2‐isopropylidene‐α‐D‐glucofuranose gave the unexpected N,N'‐di‐glucofuranosyl benzimidazol‐2‐one by a novel rearrangement and ring closure reaction. A mechanism is proposed. 相似文献
26.
The energetics and dynamics of double proton transfer (DPT) is investigated theoretically for the Watson-Crick conformation of the guanine-cytosine (GC) base pair. Using semiempirical density functional theory the isolated and DNA-embedded GC pair is considered. Differences in the energetics and dynamics of DPT thus addresses the question of how relevant studies of isolated base pairs are for the understanding of processes occurring in DNA. Two-dimensional potential energy surfaces involving the transferring hydrogen atoms and the proton donors and acceptors are presented for both systems. The DPT reaction is accompanied by a contraction of the distance between the two bases with virtually identical energetic barriers being 18.8 and 18.7 kcal/mol for the isolated and DNA-embedded system, respectively. However, the transition state for DPT in the DNA-embedded GC pair is offset by 0.1 A to larger N-H separation compared to the isolated GC pair. Using activated ab initio molecular dynamics, DPT is readily observed for the isolated base pair with a minimal amount of 21.4 kcal/mol of initial average kinetic energy along the DPT normal mode vector. On a time scale of approximately 100 fs DPT has occurred and the excess energy is redistributed. For the DNA-embedded GC pair considerably more kinetic energy is required (30.0 kcal/mol) for DPT and the process is completed within one hydrogen vibration. The relevance of studies of isolated base pairs and base pair analogs in regard of reactions or properties involving DNA is discussed. 相似文献
27.
Homoallylic ethers react with Cp2ZrCl2/2 n-BuLi reagent to afford cyclopropane derivatives. Cyclopropylcarbinyl-homoallyl rearrangements involving zirconium species are observed depending on the substrate structure. 相似文献
28.
29.
Atomic force microscopy imaging of hair: correlations between surface potential and wetting at the nanometer scale 总被引:2,自引:0,他引:2
Dupres V Camesano T Langevin D Checco A Guenoun P 《Journal of colloid and interface science》2004,269(2):329-335
We report investigations of hair surface potential under wetting at the nanometric scale by atomic force microscopy (AFM). Surface potential imaging was used to characterize the electrostatic properties of the hair samples. We found that the surface potential noticeably increases along the edges of the cuticles. These results are correlated with wetting behavior of different liquids performed using AFM in noncontact mode. 相似文献
30.
Karim Adil Gilles Dujardin Marc Leblanc Vincent Maisonneuve 《Journal of fluorine chemistry》2004,125(11):1709-1714
Tren amine cations and carbonate anions adopt a ternary symmetry while tetra amine cations are tetrahedral. The symmetry of these constitutive ions influences strongly the nature of the solids which crystallise from solutions. Large fluorinated aluminate polyanions with tetrahedral symmetry appear in the presence of tren amine, while infinite chains of AlF6 octahedra are observed with tetra amine and that noncentrosymmetric structures are frequently encountered in rare earth fluoride carbonates. 相似文献