jascm
Editor’s Choice : Potentiometric and Thermodynamic Studies of Some Azosulfoxine Derivatives and Their Metal Complexes
|
|
Abstract: The proton-ligand dissociation constants of some azosulfoxine derivatives and metal-ligand stability constants of their complexes with the metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined potentiometrically in 0.1 MKCl and 50 % (by volume) DMF–water mixture at (298, 308 and 318) K. The stability constants of the formed complexes increases in the order Mn2+, Co2+, Ni2+ and Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (∆G, ∆H and ∆S) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavourable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favourable. Keywords: Azosulfoxines, potentiometry, stability constants and thermodynamics.Download Full Article |
|
|
Abstract: The preferential solvation parameters defined as the differences between the local mole fraction of solvents around analgesic drug acetaminophen and those for the bulk co-solvent composition in propylene glycol + water mixtures were derived from their thermodynamic properties by means of the inverse Kirkwood-Buff integrals (IKBI) and the quasi-lattice-quasi-chemical (QLQC) methods. It is found that acetaminophen is sensitive to solvation effects, so according to IKBI method the preferential solvation parameter δxPG,A, is negative in water-rich mixtures but positive in medium compositions and in co-solvent-rich mixtures. It is conjecturable that in water-rich mixtures the hydrophobic hydration around the aromatic ring and methyl group present in the drug plays a relevant role in the solvation. The bigger drug solvation by co-solvent in mixtures of similar solvent proportions and in propylene glycol-rich mixtures could be due mainly to polarity effects. Otherwise, according to QLQC method, this drug is preferentially solvated by the co-solvent in all the mixtures. Keywords: Acetaminophen, propylene glycol, solubility, inverse Kirkwood-Buff integrals, preferential solvation.Download Full Article |
Editor’s Choice : Separation and Recovery of SiC Particles Discharged from Silicon Wafer Production Process
|
|
Abstract: In the slicing process of silicon wafer from silicon single crystal, it has been the general way to cut silicon by wire saws with the lubricant mixture of silicon carbide, as SiC, particles and wrapping oil. After slicing the silicon single crystal, the waste liquor containing SiC and silicon powders is discharged from the process. The particle sizes of SiC and Si are about 10μm and 1μm, respectively and the weight ratio is about 9:1. The particles discharged from slicing waste liquor become the mixture of SiC and SiO2, when the waste liquor is burned after treating the lubricant oil by a filter press. In terms of the minimization of wastes and environment, it is preferable to separate and recover the valuable SiC from SiO2. In order to solve the problem mentioned above, flotation method can be applied to accomplish the separation of SiC from SiO2. The cationic surfactants of dodecyl-tri-methyl-ammonium chloride (abbreviated as DTMAC hereafter) and tri-methyl-octyl-ammonium chloride (abbreviated as TMOAC hereafter) were used in this study. The adsorption amount of surfactants on SiC and SiO2 particles was measured. The flotation behaviors of SiC and SiO2 were investigated by changing pH, gas flow rate and flotation time in the presence of DTMAC. The purity and yield of SiC were also discussed in the flotation process comprising of roughing, cleaning and scavenging steps. A series of flotation process for SiC gave the purity and yield of 99.7% and 96.7%, respectively. Keywords: Flotation, SiC, SiO2, silicon wafer slicing waste, TMOAC, DTMAC.Download Full Article |
|
|
Abstract: Refractive indices of the binary mixtures containing an isomer of chlorobutane (1-chlorobutane, 2-chlorobutane, 2-methyl-1-chloropropane, or 2-methyl-2-chloropropane) and butyl ethyl ether have been measured at seven temperatures from T = 283.15 to 313.15 K From these data refractive index deviations were calculated and correlated with a Redlich-Kister polynomial expansion. The refractive index deviations were found positive. Finally, from these refractive indices both densities and surface tensions of the studied systems were predicted and compared with previously reported values. Keywords: Butyl ethyl ether, Isomeric chlorobutane, Predicted properties, Refractive index.Download Full Article |
|
|
Abstract: The solubility of paracetamol in N-Methyl-2-pyrrolidone (NMP) + ethanol and NMP + ethanol + water solvent mixtures at 25 °C was determined using the shake flask method. The generated data extended the solubility database of pharmaceuticals and also was used to assess the solubility prediction capability of the Jouyban-Acree model in NMP + ethanol + water mixtures. The accuracy of the predicted solubilities was evaluated by the mean percentage deviation (MPD) between the predicted and experimental solubilities. The MPD of the Jouyban-Acree model for predicting the solubility of paracetamol in NMP + ethanol + water mixtures at 25 °C was 14.6 %. Keywords: Paracetamol, binary solvents, ternary solvents, solubility prediction, pharmaceutical cosolvents.Download Full Article |