Combine cocoa and baking soda in mixing bowl; blend in 1/3 cup of the vegetable oil. Add boiling water and stir until thickened. Stir in sugar, eggs, and remaining vegetable oil; stir until batter is smooth. Stir in flour, vanilla, and salt, mixing until well blended. Fold in chopped nuts. Pour into a greased 13x9x2-inch baking pan. Bake at 350° for 35 to 40 minutes. Cool in pan on rack.