Leavening was practiced by the Eygptians, and the practice was handed down by them to the Greeks and by the Greeks to the Romans.
From the time of the Romans to the present, the use of leavening has been common. In the early days leavening was ordinarily accomplished by growing yeast or yeasts in a dough or batter rich in carbohydrates.
The mixing of baking soda and cream of tartar marked the introduction of baking powder. But the two chemicals had to be kept in separate containers until used, or else they would react if any moisture was present. And because cream of tartar was imported from France, there were the additional problems of supply and expense.
During the 1860s, various companies introduced other ingredients in their baking soda formulas and sold them as baking powders. These ingredients behaved in a more controlled way in recipes. Over time, different carbonate and acid mixtures have been sold as baking powders. Today, sodium bicarbonate and tartaric acid mixtures remain the most popular.
Before baking powder, there were mainly two ways used to make biscuits or bread light and fluffy. The first way was to add small air bubbles into the dough by beating it with a spoon or a whisk, like you would whip up whipped cream.
The second way, which is still used for most breads, is to add yeast. Yeast are microorganisms that digest sugars and produce carbon dioxide, which then forms bubbles in the dough. The development of baking powder introduced a third path to leavening dough.
Baking powder is a mixture of baking soda, starch, and at least one slightly acidic compound such as cream of tartar that works as a leavening agent in baking by releasing carbon dioxide when mixed with a liquid, such as milk or water.
It is a solid mixture that is used as a chemical leavening agent in baked goods. Baking powder is a combination of baking soda and an acid. When you add baking powder to water or milk, the alkali and the acid react with one another and produce carbon dioxide bubbles.
History and origin of baking powder 
