230 MAWS CONQUEST OF SUBSTANCES 



der. When soda and cream of tartar are mixed dry, they do 

 not react on each other, neither do they combine rapidly in 

 cold moist dough, but as soon as the heat of the oven pene- 

 trates the doughy mass, the cream of tartar combines with 

 the soda and sets free the gas needed to raise the dough. 

 The gas expands with the heat of the oven, raising the dough 

 still more. Meanwhile, the dough itself is influenced by the 

 heat and is stiffened to such an extent that it retains its in- 

 flated shape and spongy nature. 



Many housewives look askance at ready-made baking pow- 

 ders and prefer to bake with soda and sour milk, soda and 

 buttermilk, or soda and cream of tartar. Sour milk and butter- 

 milk are quite as good as cream of tartar, because the lactic 

 acid which they contain combines with the soda and liber- 

 ates carbon dioxide, and forms a harmless residue in the 

 dough. 



The desire of manufacturers to produce cheaper baking 

 powders led to the use of cheap acids and alkalies, regardless 

 of the character of the resulting salt. Alum and soda were 

 popular for some time ; but careful examination proved that 

 the particular salt produced by this combination was not 

 readily absorbed by the stomach, and that its retention there 

 was injurious to health. For this reason, many states have 

 prohibited the use of alum in baking powders. 



It is not only important to choose the ingredients carefully ; 

 it is also necessary to calculate the respective quantities of 

 each, otherwise there will be an excess of acid or alkali for 

 the stomach to take care of. A standard powder contains 

 twice as much cream of tartar as of bicarbonate of soda, and 

 the thrifty housewife who wishes to economize, can make for 

 herself, at small cost, as good a baking powder as any on the 

 market, by mixing tartar and soda in the above proportions 

 and adding a little corn starch to keep the mixture dry. 



