Why do some recipes ask for both bicarbonate of soda and baking powder when they both do the same thing?

Just wondering.Why do some recipes ask for both bicarbonate of soda and baking powder when they both do the same thing?
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http://chemistry.about.com/cs/foodchemistry/f/blbaking.htmWhy do some recipes ask for both bicarbonate of soda and baking powder when they both do the same thing?
They do the same thing, but they work in slightly different ways. Baking soda needs an acid to help it work right. Baking powder has the acid already put into it, so that you don't need any acid in the recipe. If find that when it's a mix, there is a little acid in the recipe for some baking soda, but not enough to put enough baking soda to give it the rise it needs, so they add some baking powder as well.
Garbage Kills Megan pretty much nailed it. With ';double acting'; baking powder (almost all of it is these days) you get an initial round of leavening when liquids activate it, and then another round of activity that is heat triggered. Baking soda has to have an acidic ingredient to work correctly in a recipe, and you've got to work fast.
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That site lists almost all Recipes.


Not only the recipe you are looking for but also other popular recipes.