Solvates of Indomethacin

Indomethacin is known to exhibit polymorphism and solvates, the different forms obtained do not exhibit the same solubility and their bioavailabilities are different. It is of a prime importance to identify the various polymorphic and solvated forms. This study was carried out by: DSC (different scanning calorimetry), TG (thermogravimetric analysis), X-ray diffraction and thermomicroscopy. Seven solvates, with acetone, benzene, dichloromethane, tetrahydrofurane, propanol, chloroform and diethylether, were isolated and studied. Their formulae have been determined by thermogravimetric analysis and their X-ray patterns on powder are presented, by DSC their behaviour after desolvation is recorded, the temperature and the enthalpy of fusion are measured and by this way the form obtained is deduced. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tl2Te and its relationship with Tl5Te3

The crystal structure of Tl₂Te, dithallium telluride, has been determined by single‐crystal X‐ray diffraction. The analysis of the structure shows that this compound is the first known representative of a new crystal structure type. The structural relationship with the related Tl₅Te₃ phase is discussed.     

Etude de la transition de phase du compose Sb.405Te.595 entre 630 K et 665 K

The present study was performed in an attempt to confirm the existence of the Sb_.405Te_.595 phase transition by employing drop calorimetric method and high temperature X-ray diffractometry. Heat capacity of Sb_.405Te_.595, in the solid state is deduced. Low and high temperature X-ray powder data are given.

---

Zusammenfassung Diese Arbeit beschäftigt sich mit dem Nachweis der Existenz der Sb_.405Te_.595 Phasenumwandlung mittels Dropkalorimetertechnik und Hochtemperaturröntgendiffraktometrie. Es wird die Wärmekapazität von Sb_.405Te_.595 im festen Zustand abgeleitet sowie Daten von Nieder- und Hochtemperaturröntgenpulveraufnahmen gegeben.

---

Sb_0,405Te_0,595. . - .

     

Diagramme de phases du systeme binaire AgNO3—RbNO3

Phase diagram of the binary system AgNO₃—RbNO₃ was studied using thermal analysis technique, differential scanning calorimetry and X-ray diffraction. This binary exhibits a congruently melting compound Ag_0.5Rb_0.5NO₃ (m. p.=138°C), an incongruently melting one Ag_0.33Rb_0.66NO3 with two polymorphic varieties, two eutectics at (36 mol% RbNO₃, 128°C) and at (60 mol% RbNO₃, near 134°C) respectively and a peritectic at (60.5 mol% RbNO₃, 141°C). This system contains also three invariant reactions at 164, 222 and 282°C due to the phase transitions of RbNO₃ and another one at 164°C due to the phase transition of AgNO₃.

Ce travail a été présenté aux 32èmes JCAT, tenues à Hammamet, TN, du 12 au 14 Mai 2001.     

Enthalpies de melange du systeme antimoine-tellure a 909,30 K, 911,85 K et 917,95 K

Thermodynamical data on Sb-Te system at 909,30 K, 911,85 K and 917,95 K. The integral molar enthalpies of formation of liquid Sb-Te alloys were measured at three temperatures by drop calorimetry.Partial molar enthalpies of formation of these alloys, referring to the pure liquid constituants, and enthalpie of formation at 298 K of the compound Sb₄₀₅Te₅₉₅ were deduced.

---

Zusammenfassung Thermodynamische Daten, des Systemes Sb-Te bei 909,30, 911,85 und 917,95 K. Mittels Drop-Kalorimetrie wurden die integralen molaren Bildungsenthalpien von flüssigen Sb-Te Legierungen bei drei verschiedenen Temperaturen gemessen. Die partiellen molaren Bildungsenthalpien dieser Legierungen, bezogen auf die reinen flüssigen Komponenten sowie die Bildungsenthalpie der Verbindung Sb_0.405Te_0.595 bei 298 K wurden abgeleitet.

---

Sb-Te 909,30; 911,85 917,95 . , Sb_0.4050.595 298 .

     

Polymorphic and Thermodynamic Study of Indomethacin

Indomethacin is known to exhibit polymorphism. As a consequence the various forms have different solubilities and may have different bioavailabilities. This study has been carried out with the following techniques: calorimetry, differential scanning calorimetry (DSC), thermogravimetric analysis (TG), X-ray diffraction and thermomicroscopy. Two solid forms have been prepared and studied: their melting temperature and their enthalpy of fusion are determined. The heat capacity and heat content were measured vs. the temperature for these two solid forms and for the liquid phase. This is fundamental for the determination of the stable form. More of this, with a view to study phase diagrams of indomethacin with another compound (solvent or not), the knowledge of the C _p of the various forms is necessary for calculation of the liquidus curve, this allows to minimize the number of experiments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Importance of heat capacity determination in homogeneous nucleation: application to progesterone

Progesterone is known to exist under different crystallographic forms in the solid state. The thermodynamic stable form (I), melts at 129.2 °C (402.35 K) under atmospheric pressure. After melting and cooling a metastable form (II) can be obtained which melts at 122 °C (395.15 K). This uncommon behaviour can be explained with the theory of nucleation, only if heat capacity of the different forms are known.     

Capacite calorifique molaire du compose Sb·405Te·595 dans les etats solides et liquides entre 298 K et 922 K

Heat capacity (C _p ) of the compound Sb_·405Te_·595 in solid and liquid states at constant pressure are calculated from the results of experimental drop calorimetric method. The heat of fusion of the compound is deduced. A phase transition in the solid state has been put in evidence.

---

Zusammenfassung Basierend auf Ergebnissen einer Dropkalorimetrie-Methode wurde die Wärmekapazität für konstanten Druck (C _p ) der Verbindung Sb_·405Te_·595 für den festen und flüssigen Aggregatzustand errechnet und die Schmelzwärme der Verbindung abgeleitet. Ein Phasenübergang im festen Zustand wurde vorausgesetzt.

---

, , (C _p ) Sb_0.405Te_0.595 , . .

     

Low pressure phases Thermodynamic properties of the γ-aminobutyric acid

A metastable form of γ-aminobutyric acid has been prepared by sublimation under vacuum. A theoretical unary phase diagram has been deduce from experimental thermal analysis. Aqueous solution of γ-aminobutyric acid (Gaba) prepared from commercial product (monoclinic) does not cross blood–brain barrier after intra peritoneal administration to mice, hence it displays no anticonvulsion activity. Therefore, we developed a polymorphic form, the solution of which presents such activity. In the present paper the preparation and the physico-chemical properties are reported.