If a recipe calls for 1 table spoon of baking soda it will call for a acidic liquid such as buttermilk or lemon juice for levening. You can substitute with baking powder but have to use instead of acid milk or water. Because baking powder is baking soda with a dry acid moisture activates. You can reverse this recipe if you had baking soda an no baking powder. For instance you would use 1 tablespoon baking soda to the 3 1/2 teaspoon and 1/3 cup buttermilk to the 1/3 cup milk because baking soda requires a acid for levening. Any questions ask but all over the web I looked this was my on experiment.