2.1.2. Chemicals and solutions
All chemicals used were of analytical grade except sodium
methylate that was an industrial product (30% w/w). Water was
obtained from a glass bidistillator. Vegetable oils and animal fats
were obtained in the local market.
Iodine standard solution, 0.1 mol L1: prepared by dissolving
25.38 g of metallic iodine in 1000 mL of 96% ethyl alcohol in a volumetric
flask. The solution was stored in a brown bottle and kept in
a refrigerator.
Thiosulfate solution, 0.1 mol L1: prepared by dissolving 24.9 g of
sodium thiosulfate pentahydrate (Na2S2O35H2O) in 1000 mL of
boiled bidistilled water. The solution was standardized with a
0.02 mol L1 potassium permanganate standard solution and
stored in a brown bottle.