Baking powder
This is made from bicarbonate of soda (baking soda) and a mild acid (usually cream of tartar). When moist and warm, these chemicals react and give off carbon dioxide, causing foods to rise.
Uses: Scones, cakes, puddings, biscuits and batters. The proportion of baking powder required will differ depending on the recipe.
To store: Store in a cool, dry cupboard.