Kinetics of thermal decomposition of Co3O4 powder and single crystals

Kinetics of thermal decomposition in vacuum of Co₃O₄ powder as well as single crystals has been investigated. Discrepancies with the results of previous authors have been discussed. Decomposition of Co₃O₄ proceeds through formation of a compact layer of CoO and hence diffusion is the rate-limiting factor. The experimental curves α(t) be described for 0.05 < α < 0.85 using a modified Ginstling-Brounshtein equation: 1 ? 2α/3 ? (1 ? α)^2/3 = ktⁿ where the activation energy varies with the degree of decomposition.     

Hydrothermal phase equilibria in Ln2O3-H2O systems

Hydrothermal phase equilibria studies have been carried out in the Ln₂O₃-H₂O systems (Ln = La, Pr, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and the stability fields of the phases Ln(OH)₃ LnOOH and Ln₂O₃-C have been established in the pressure-temperature range of 25000 psi and 900° C. The sequioxides Ln₂O₃-C are stable only in the last four systems of Er to Lu along with the Ln(OH)₃ and LnOOH. The systems from Nd to Ho have only Ln(OH)₃ and LnOOH as stable phases and those from La to Pr have only Ln(OH)₃ as the stable phase. The unit cell parameters of trihydroxides deviate from the values reported in the literature and this is attributed to the contamination of CO₂ in the starting material.     

Trichosides A and B,new withanolide glucosides from Tricholepis eburnea

Trichosides A (1) and B (2), new withanolide glucosides, have been isolated from the n-butanolic fraction of the 75% methanolic extract of aerial parts of Tricholepis eburnea. Their structures were elucidated through spectroscopic analysis including ESI-MS, 2D NMR and acid hydrolysis.     

A simple but very close approximation to the Serin-Ellickson equation

The Serin-Ellickson equation, {fx367-1} whereD is the diffusion coefficient anda the radius of a spherical body, can be approximated with high accuracy in a wide range of α values by {fx367-2} where {ie367-1}.     

Armatans A and B,New Antimicrobial Isoflavans from Colutea armata

Chemistry of Natural Compounds - Armatans A (1) and B (2), new isoflavans, have been isolated from the EtOAc-soluble fraction of the MeOH extract of Colutea armata Hemsl. &amp; Lace, along with...     

New terpenoids from Stachys parviflora Benth

Two new triterpenoidal saponins were isolated from the n-butanolic extract of Stachys parviflora (Lamiaceae). Their structures were elucidated on the basis of spectral data as stachyssaponin A; 3beta, 15alpha, 19alpha, 21beta, 22alpha-pentahydroxyolean-12-ene-28-oic acid 3-O-{alpha-L-rhamnopyranosyl-(1 --> 3)-beta-D-glucopyranoside}-22-O-{alpha-L-arabinofuranosyl-(1 --> 3)-beta-D-glucopyranoside} (1) and stachyssaponin B; 2beta, 3beta, 15alpha, 21beta-tetrahydroxyolean-12-ene-28-oic acid 2-O-[alpha-L-arabinofuranoside]-3, 21-bis-O-[beta-D-glucopyranoside] (2).     

New ceramides from Platytaenia multicaule

Phytochemical investigation of Platytaenia multicaule resulted in the isolation of two new ceramides, N-triacontylpentadecanamide and 1,3,4-trihydroxy-2,dodecanoylamino-(24E)-unacotenene, along with two known compounds, beta-sitosterol and beta-sitosterol glycoside. The structure elucidation of the isolated compounds was based primarily on 1D and 2D NMR analyses, including COSY, NOESY, HMQC, and HMBC correlations.     

Decarbonation curves and associated thermodynamic data for synthetic Cd-dolomites CdMg(CO3)2, CdMn(CO3)2 and CdZn(CO3)2

Decarbonation curve for the synthetic dolomite analogues; (Cd-dolomites) were determined for CdMg(CO₃)₂, CdMn(CO₃)₂ and CdZn(CO₃)₂ under CO₂ pressure of up to 2.5 kbar. All the three double carbonates were completely disordered at the decomposition temperatures and hence the thermodynamic data (Standard enthalpy; ΔH _f ^o, Standard free energy; ΔG _f ^o) retrieved from the univariant decarbonation curve corresponds to the disordered phases. They are: The mixing enthalpies and free energies for the formation of the disordered 1∶1 solid solution phases are: The thermodynamic data (ΔH _f ^o, ΔG _f ^o and ΔH _r ^o, ΔG _r ^o) showed a positive correlation with the decomposition temperatures. The mixing energies of the disordered double carbonates also show a direct correlation with the cationic size differences.     

Thermal decomposition of rhombohedral double carbonates of dolomite type

DTA and TG studies in air were carried out for hydrothermally prepared rhombohedral double carbonates of dolomite type, CaMg(CO₃)₂, CaMn(CO₃)₂, CdMg(CO₃)₂, CdMn(CO₃)₂ and CdZn(CO₃)₂. The solid decomposition products in air have been compared to those obtained under hydrothermal conditions with CO₂ pressure. The dolomite [CaMg(CO₃)₂] decomposes in two stages both in air as well as under high CO₂ pressure. The other carbonates studied, follow a single stage decomposition in air and a two stage decomposition under hydrothermal condition. In air, the manganese containing carbonates CaMn(CO₃)₂ and CdMn(CO₃)₂, decompose to form mixed oxides of CaMnO₃ and CdMnO₃ respectively, while CdMg(CO₃)₂ and CdZn(CO₃)₂ decompose to their respective two mono oxides.     

Gnapholide: a new guaiac-dimer from Pulicaria gnaphalodes (Asteraceae)

The ethyl acetate soluble part of the chloroform extract of Pulicaria gnaphalodes belonging to the family Asteraceae afforded a new sesquiterpene-dimer of guaiane class named as gnapholide and anabsinthin of the same skeleton. The structures of both the compounds were elucidated with the aid of spectroscopic techniques including 2D NMR.