The Thermodynamic Properties of Some Acacia Gums

Abstract

Fourty gum samples from A.nilotrca var. nilotica and A.seyal var. seyal represented by eight composite samples were collected from eight locations within the sudan gum belt with different soil types. The locations are Eldamazien, Eldinder ,Sinnar and Elgazira. Which represented the clay soil areas where as Alnihud ,Alobied, Abuzabad and Aburay represented the sandy soil areas of the belt . Characterization studies, which are partly used for authentication of samples and resources, include the determination of moisture, ash, pH, nitrogen and protein content . Average moisture, ash, pH, nitrogen and protein content of A.nilotica var. nilotica were found to be 10.87%, 1.86%, 5.1, 0.023% and 0.151% respectively. For A.seyal var. seyal they were found to be 11.3%, 2.82%, 3.4, 0.133%, and 0.88%. Intrinsic viscosities, specific rotation, acid equivalent weight and total uronic acid of A.nilotica var. nilotica were found to be 10.1 cm3 g-1,+92.6 ,1866.76 and 10.42 % respectively . While for A.seyal var.seyal they were found to be 12.12cm3 g-1, +55.25, 1449.93 and 13.38% respectively. Cationic composition studies show that potassium has the highest value followed by calcium, magnesium, sodium, lead, iron and zinc. Sugar composition shows average values of galactose content of A.nilotica var. nilotica and A.seyal var. seyal were found to be 16.34% and 38.06% respectively ,and arabinose content were found to be 45.90% and 42.33% respectively. While rhamnose was found to be10.33% and 3.67% respectively. The number average molecular weight value was found to be 2.10×105for composite samples of A.nilotica var. nilotica. For composite samples of A.seyal var. seyal was found to be 2.97×105. Thermodynamic studies involved the estimation the partial specific volume of gum, partial specific volume of the solvent and the volume fraction. For composite samples of A.nilotica var. nilotica average was found to be 0.642 cm3 g-1, 0.998cm3g-1, 0.39024, and 0.61584 respectively. While average for composite samples of A.seyal var. seyal were found to be 0.647cm3g-1, 0.998cm3g-1, 0.3931, and 0.6065 respectively. iv Chemical potential range have been calculated from osmotic measurement for different concentrations and was found to be –1.610715×10-3 to -2.13658×10-3 joule g-1 on average for composite samples of A.nilotica var.nilotica. For composite samples of A.seyal var.seyal the average it was found to be -1.17945×10-3 to -1.57519×10-3 joule g-1. Second virial coefficient (A2) average for composite samples of A.nilotica var.nilotica were found to be 1.11×10-3. Where as for composite samples of A.seyal var.seyal was found to be 3.51×10-3. Free energy of mixing range of composite samples of A.nilotica var. nilotica average was found to be (-1.33470×10-3 to -3.40428×10-3). For composite samples of A.seyal var.seyal average was found to be (-2.112877×10-3 to -5.966130×10-3).