الخصائص الثيرموديناميكية لمحلول صمغ الكوك

Abstract

Physio-chemical characterization and thermodynamic properties of a composite sample of Acacia sieberana var. sieberana gum from White Nile State were studied using standard methods. Different characterization methods were used to obtain the average values of: moisture, ash, pH, specific rotation, refractive index, intrinsic viscosity, nitrogen and protein content of the gum. The values were found to be: 8.65 %, 1.665 %, 5:0, +93ᵒ, 1.336, 10.47ml g-1, 0.41 % and 2.71% respectively. The molecular weight of the gum was estimated using osmotic pressure measurement and found to be 2.9 x 106 Da. Thermodynamic parameters of the gum solution including the partial specific volume of the gum and that of the solvent (water) and their volume fractions were estimated and found to be 1.151 cm3g-1 , 1.054 cm3g-1, 0.522 and 0.478 respectively. The chemical potential of A. sieberana have been calculated from osmotic pressure measurement for different concentration of the gum solutions and were found to be in the range (-2.03 to -20.63) Jg-1. The second virial coefficient was found to be The free energies of mixing were also determined for different solutions and their values were found to be in the range (-0.09 to -1.54) 10-2Jg-1 of gum solution or (-1.67 to -29.52) 10-2 J mol-1 of gum solution) respectively.