Interesting article: What's the Difference Between Dutch Process and Natural Cocoa Powder?
Natural cocoa is acidic, and the acidity of your ingredients affects the leavening you should use.
Even more enlightening: Baking Basics: Baking Powder vs Baking Soda
Natural cocoa is acidic, and the acidity of your ingredients affects the leavening you should use.
Even more enlightening: Baking Basics: Baking Powder vs Baking Soda