Baking soda in shampoo as a deep cleaner?

I read in a magazine that if you add a certain amount of baking soda to a quarter sized thing of shampoo you could use it as a clarifying shampoo. Does anyone know how much baking soda to use?Baking soda in shampoo as a deep cleaner?
Use about two tablespoons and mix until the baking soda is in a fine grain.