Dissolve soda in buttermilk; stir well. Combine flour and salt; cut in shortening until mixture resembles coarse meal. Sprinkle buttermilk mixture evenly over flour mixture, stirring until dry ingredients are moistened.
Turn dough out onto a lightly floured surface; knead 4 to 5 times.
Roll dough to 1/2-inch thickness; cut with a 2-inch biscuit cutter. Place biscuits on a greased baking sheet. Bake at 475° for 10 minutes or until lightly browned.