CHEMISTRY OF BAKING 25 



baking. The carbon dioxide is what raises the dough 

 when baking soda is used. If the soda is not completely 

 dissolved and mixed with the dough, yellow spots will 

 appear in the bread or biscuits. One sure way of pre- 

 venting this is to dissolve the soda in water and then 

 mix it with the flour or dough. A less sure way of pre- 

 venting the yellow spots is to sift the soda with the flour. 



When baking soda in solution or in the dough is heated, 

 carbon dioxide is liberated, and another salt called wash- 

 ing soda (Na 2 CO3) is formed. This stays in the bread 

 and is not healthful. 



20. Baking Powder. Baking powder is a mixture of 

 two salts and some corn starch to keep it dry. Baking 

 powder does not form washing soda in the bread and so 

 is better for baking than soda. The object in using any 

 such compound in baking is to liberate carbon dioxide 

 to raise the dough. Carbon dioxide will be liberated if 

 baking soda is used with an acid. Hence, in making 

 baking powder, baking soda is mixed with a mild acid 

 salt which will not form a harmful salt in the bread. 

 (Caution. Sometimes in making baking powder a 

 cheap acid is used that will form a harmful substance 

 in the cake or bread. These are called the alum baking 

 powders and they should not be used.) 



The good baking powders are made of two parts of 

 cream of tartar (KHC 4 H 4 Oe), one part of baking soda, and 

 some corn starch. Tartaric acid (HC 4 H 4 O 6 ) and calcium 

 acid phosphate [CaH 4 (PO 4 )2] may also be used with 

 baking soda to make the baking powder. The sub- 

 stances formed in the bread by these powders are 

 perfectly harmless. 



In making baking powders baking soda is mixed with 

 the acidic salts, but no chemical action will take place 



