Lye, baking soda and ammonia are examples of common alkaline substances. The word alkaline describes a water-based solution with a pH above 7.0.
While common household lye usually refers to sodium hydroxide, the word originally referred to potash, a substance leached from hardwood ashes using water. Although lye is caustic and poisonous, manufacturers use it in the production of food, including pretzels, green olives, lutefisk and Chinese noodles. Because lye creates heat when dissolved in water and helps to dissolve grease, drain cleaner manufacturers often use it in their products. Lye is also used in manufacturing soap.
Baking soda is mildly alkaline. Bakers use it in breads and cakes mixed with an acid, such as vinegar or lemon juice, to create carbon dioxide bubbles that cause their products to be lighter in texture. Baking powder contains baking soda and cream of tartar, a mild acid. When the two mix with liquids, they form the same gas bubbles.
Ammonia is a highly caustic alkaline substance. It has a strong and recognizable smell. Farmers apply ammonia to the soil to increase the available nitrogen. Ammonia is a powerful degreaser that requires proper ventilation when using indoors.