Equivalents and Substitutions
Substitute 1/4 teaspoon of lemon juice or white vinegar for each 1/8 teaspoon cream of tartar called for to stabilize egg whites. Keep in mind that vinegar may alter the taste of the final product.
When cream of tartar is used in a recipe with baking soda, it works like a double-acting baking powder. If cream of tartar is not available, substitute baking powder for both the baking soda and cream of tartar called for in the recipe. Use 1 teaspoon baking powder for every 1/4 teaspoon baking soda plus 1/2 teaspoon cream of tartar.