Shamim Akhtar

Density and Viscosity of 1-Alkanols

Densities and viscosities have been measured for twelve 1-alkanols from methanol to 1-dodecanol at temperatures ranging from 303.15 to 323.15 K. Molar volumes, V m , have been calculated from the density data, which have been found to follow the additive equation, V m  = V CH3  + nV CH2  + V OH, where n is the number of CH2 groups. V m have been plotted against n, showing an excellent linear relationship. The average values of V CH2 at 303.15 K and 323.15 K have been determined from the slopes of this equation. The viscosities have been found to increase almost exponentially with the number of carbon atoms at different temperatures. The thermodynamic activation parameters, free energy, ▵G ≠, enthalpy, ▵H ≠, and entropy, ▵S ≠ for viscous flow have been plotted against the number of C atoms – all have been found to increase with the chain length of 1-alkanols.

Viscosity of Aqueous Solutions of Formamide, N-Methylformamide and N,N-Dimethylformamide

Abstract Viscosities of aqueous solutions of formamide, N-methylformamide and N,N-dimethylformamide have been measured at temperatures 303.15, 308.15, 313.15, 318.15 and 323.15 K. For formamide + water system the viscosity increases exponentially with respect to the mole fraction of formamide. In contrast, N-methylformamide+water and N,N-dimethylformamide+water systems exhibit maxima in water-rich region, the maxima of the latter being higher and sharper than those of the former system. The excess viscosities of formamide+water system are positive at 323.15 K, which turn to negative values at 303.15 K, the magnitude of the values being very small irrespective of their sign. On the other hand, N-methylformamide+water and N,N-dimethylformaide+water systems show large positive excess viscosities for the whole range of composition. The viscosities and excess viscosities for the system formamide+water have been explained by assuming some complex formation between the components with the simultaneous disruption of water structures. For N-methylformamide+water and N,N-dimethylformamide+water systems, it has been assumed that cluster-like structure of water is formed around methyl group(s) attached to N-atom of the amides, which influences the viscosity behaviour of these systems strongly.

Viscosity of aqueous solutions of some alcohols

Abstract Viscosities of aqueous solutions of 1-Propanol, 2-Propanol, t-Butanol, allyl alcohol and propargyl alcohol were measured at temperatures 30°, 35°, 40°, 45° and 50°C covering the whole range of composition. On addition of alcohols to water, viscosity increases rapidly. Except for propargyl alcohol, viscosities pass through maxima and then decline continuously as the addition of alcohol is continued. the heights of the maxima occuring between 0.2 and 0.3 mole fraction of alcohols are in the order, t-Butanol > 2-Propanol > 1-Propanol > allyl alcohol. Contrary to this, propargyl alcohol shows no such maximum. After the fast initial rise, the viscosity rises slowly and monotonically up to its pure state for this alcohol. the excess viscosities are found to be positive and large in magnitude. for all alcohols, excess viscosities show maxima in water-rich region. Shallow minima are observed for 2-Propanol and t-Butanol, each at the alcohol-rich end of viscosity curves, which disappear gradually with the...

Excess Molar Volumes and Thermal Expansivities of Aqueous Solutions of Dimethylsulfoxide, Tetrahydrofuran and 1,4-Dioxane

Densities, , of the systems water (W) + dimethylsulfoxide (DMSO), W + tetrahydrofuran (THF) and W + 1,4-dioxane (DO) have been determined in the temperature range 303.15-323.15 K. Excess molar volumes,

Excess Molar Volumes of Aqueous Solutions of 1-Propanol, 2-Propanol, Allyl Alcohol and Propargyl Alcohol

V_m^E

Viscosity of Aqueous Solutions of n-butylamine, sec-butylamine and tert-butylamine

, have been found to be negative and large in magnitude. Thermal expansivities, f , and excess thermal expansivities, f E , have been calculated. Densities, excess molar volumes, thermal expansivities and excess thermal expansivities have been plotted against mole fraction of solutes. All these properties have been expressed satisfactorily by appropriate polynomials. Attempt has been made to explain

Viscosities of Aqueous Solutions of Dimethylsulfoxide, 1,4-Dioxane and Tetrahydrofuran

V_m^E

Viscosity of aqueous solutions of some diamines

in terms of hydrophobic hydration and hydrophilic effect of the solutes.

Excess molar volumes of aqueous solutions of butylamine isomers

Abstract Excess molar volumes, VE have been claculated from the density data of aqueous solutions of 1-propanol, 2-propanol, allyl alcohol and propargyl alcohol at temperatures ranging from 30°-50°C. The VE values have been found to be negative at all temperatures. The volume contraction for saturated alcohols, both straight and branched chain, in aqueous media is accounted for mainly by the hydrophobic effect, while that for unsaturated alcohols is explained primarily by the formation of H-bond between the alcohol and water. The dVE/dT values have been found to be positive for all alcohols. The temperature dependence of VE is thought to be strongly influenced by the structural properties of water.

Density, viscosity and thermodynamic activation of viscous flow of water + acetonitrile

Abstract Viscosities of the systems, water (W) + n-butylamine (NBA), W + sec-butylamine (SBA) and W + tert-butylamine (TBA) have been measured in the temperature range 298.15–323.15K. The viscosities (η) and excess viscosities (ηE) have been plotted against mole fraction of amines (X 2). On addition of amines to water, viscosities first increase rapidly, then pass through maxima at 0.2 mole fraction of amines and then decline continuously as the addition of amines is continued. ηE show large positive values, with maxima also at 0.2 mole fraction of amines. The maxima of the curves of η and ηE vs. mole fraction of butylamines follow the order, W + TBA > W + SBA > W + NBA. The ascending part of the η vs. X 2 curves in the water-rich region is explained by the hydrophobic hydration caused by the hydrocarbon tails and the hydrophilic effect due to — NH2 group of amines. Following the maxima, amine - amine association is preferred, which accounts for the steady decrease of viscosity up to the pure state of amines.