In this paper we describe the chemical reactions of leavening agents in baking biscuits on a sound thermodynamic basis. The model is part in a sequel targetted at physical understanding of biscuit baking with the purpose of reformulation of biscuits with respect to sucrose and sodium levels. The chemical leavening gases. CO2 and NH3. https://www.reesfrashers.shop/product-category/t-shirts-cleethorpes-hoodies/