K.C. Singh

Molar excess Gibbs free energy of 1-Propanol or 2-Propanol + aromatic hydrocarbons at 298.15 K in terms of an association model with a Flory contribution term

Molar excess Gibbs free energy of mixing values for 1-propanol or 2-propanol + benzene, toluene, o- m- or p-xylene at 298.15 K have been calculated by the Barker method from vapour pressure data measured by a static method. The free energies of mixing for these binary systems are also predicted in terms of the Mecke-Kempter type of association model with a Flory contribution term using two interaction parameters. The predicted values agree reasonably well with the experimental values.

Excess enthalpies and volumes of mixing of 1-propanol or 2-propanol + cyclohexane at 298.15 and 308.15 K

Abstract Excess molar enthalpies and excess molar volumes at 298.15 and 308.15 K are reported for 1-propanol or 2-propanol with cyclohexane. The analysis in terms of Mecke-Kempter association model with a Flory contribution term and generalized quasi-lattice model by Barker is described.

Excess molar enthalpies of mixing of 1-propanol or 2-propanol with aromatic hydrocarbons at 308.15 K in terms of an association model

Heat of mixing data for 1-propanol or 2-propanol with benzene, toluene, o-xylene, m-xylene and p-xylene at 308.15 K have been reported. The analysis in terms of the Mecke-Kempter association model with a Flory contribution term and generalized quasi-lattice model by Barker is described.

Excess heat of mixing of 1-propanol or 2-propanol with benzene, toluene, o-, m- and p-xylenes at 298.15 K

Excess heat of mixing data at 298.15 K for 1-propanol or 2-propanol with benzene, toluene, o-xylene, m-xylene or p-xylene have been reported. Analysis in terms of the Mecke-Kempter association model with a Flory contribution term and generalized quasi-lattice model by Barker is described.

Excess molar enthalpies of 2-methylpropan-1-ol with aromatic hydrocarbons at 308.15 K in terms of an association model with a Flory contribution term

Abstract Excess molar enthalpies at 308.15 K are reported for 2-methylpropan-1-ol with benzene, toluene, o-, m- and p-xylene over the entire range of composition. The analysis in terms of an athermal associated mixture model (Mecke–Kempter type) with a Flory contribution term and quasi-chemical model by Barker is described. Association model predicts good agreement with VE data, while the prediction of both association model and quasi-chemical model are fairly good for HE data.

Excess molar Gibbs free energies of ethyl iodide plus aromatic hydrocarbons at 308.15 K

Abstract Excess molar Gibbs free energies GEm for (ethyl iodide plus benzene, toluene, o-xylene, m-xylene or p-xyleae) over the whole range of composition have been measured experimentally at 308.15 K from the measured vapour pressures. The results for GmE values of these mixtures suggest the existence of weak specific interactions of electron donor-acceptor type in which aromatic hydrocarbons behave as electron donors. The values of GmE have also been computed from the statistical theory of Flory. The Flory theory gave poor agreement between experimental and calculated values.

Excess molar Gibbs energies of 2-methylpropan-1-ol with benzene or toluene or o- or m- and p-xylene at 308.15 K in terms of an association model

Abstract Excess molar Gibbs energy values for 2-methylpropan-1-ol+benzene or toluene or o- or m- and p-xylene at 308.15 K have been calculated by Barker method from vapour pressure data measured by a static method over the entire range of composition. The excess Gibbs energies for these binary systems are also analysed in terms of the Mecke–Kempter type of association model with a Flory contribution term using two interaction parameters.

Color stability of aesthetic restorative materials after exposure to commonly consumed beverages: A systematic review of literature

Accurate shade matching of tooth colored restoration with the adjacent dentition is essential not only at the time of fabrication but also for the life time durability. This is a factual truth for dental porcelain but in contradiction, color instability in porcelain restoration is a common dilemma nowadays, especially when they are exposed to routinely consumable beverages, which sever its nature of being tooth colored. Here the authors have attempted to highlight the historical outlooks, researches on color stability and difficulties, and current trends for color stability in tooth colored restorative materials, predominantly dental ceramics. A methodical literature search was performed using MEDLINE/PubMed and other scholarly research bibliographic databases using Medical Subject Headings (MeSH) from 1953 to 2013. Most of the studies suggest and evidence that there is no ceramic available, which could be classified as total stain free; however, there is wide diversity in their color stability and surface characteristics seen with different oral conditions both qualitatively and quantitatively.

Three-dimensional analysis to compare parallelism of occlusal planes to the hamular notch-incisive papilla plane in dentulous and edentulous subjects

Purpose and Aim: The aim of this study was to evaluate the reliability of hamular notch-incisive papilla (HIP) plane as an anatomical landmark in establishing occlusal plane in edentulous subjects. Materials and Methods: Seventy subjects were selected from the South Indian population, of which 50 were dentulous and 20 were edentulous. Dental stone casts were fabricated for dentulous and edentulous subjects. Dental stone casts of the dentulous and edentulous subjects, along with occlusal rims were analyzed using the three-dimensional analyzing machines. The angles between the occlusal planes and HIP plane were determined using the reference coordinate system based on characteristic points in the dentition on the cusp tips in dentulous casts and on maxillary occlusal rim on edentulous casts. Results: The HIP plane tends to be parallel to the occlusal plane. There is no statistical difference between sexes. Conclusion: The HIP plane is parallel to the natural occlusal plane and can be used as a reference plane to re-establish the occlusal plane in edentulous patients.

Excess volumes of mixing and excess enthalpies of mixing of n-butyl chloride with aromatic hydrocarbons at 298.15 K

Abstract The excess volumes and enthalpies of mixing of binary mixtures of n -butyl chloride with benzene, toluene, o -xylene, m -xylene and p -xylene have been measured experimentally over the whole composition range at 298.15 K. The data have been analysed qualitatively in terms of the specific interactions of electron donor-acceptor type and of the disruption of molecular order in the pure components. Florys theory correctly predicts the sign and to an acceptable extent the magnitude of the H E values although the agreement for V E values is not good. However, the Graph theory correctly predicts the sign as well as the magnitude of the V E and H E values.