What is the difference between baker's yeast and the raising agent known as "chemical yeast" ?
Baker's yeast is a living product. Its cells have the property of transforming the sugars naturally present in flour into alcohol (which disappears during baking) and into carbon dioxide. This latter is what makes your bread dough rise.
Raising agents or chemical yeasts are composed of bicarbonate and mineral salts, and not of living cells, as in baker's yeast. They react chemically in the presence of water.
Raising agents are suitable for Genoese sheets, but cannot be used in bread, pizza or brioche recipes… to which baker's yeast is perfectly suited.