ely simple
means; that is, by treating salt with the base, ammonia, and with
carbon dioxide.

Washing soda has already been discussed. Since baking powders in some
form are used in almost all homes for the raising of cake and pastry
dough, it is essential that their helpful and harmful qualities be
clearly understood.

The raising of dough by means of baking soda--bicarbonate of soda--is
a very simple process. When soda is heated, it gives off carbon
dioxide gas; you can easily prove this for yourself by burning a
little soda in a test tube, and testing the escaping gas in a test
tube of limewater. When flour and water alone are kneaded and baked
in loaves, the result is a mass so compact and hard that human teeth
are almost powerless to crush and chew it. The problem is to separate
the mass of dough or, in other words, to cause it to rise and lighten.
This can be done by mixing a little soda in the flour, because the
heat of the oven causes the soda to give off bubbles of gas, and these
in expanding make the heavy mass slightly porous. Bread is never
lightened with soda because the amount of gas thus given off is too
small to convert heavy compact bread dough into a spongy mass; but
biscuit and cake, being by nature less compact and heavy, are
sufficiently lightened by the gas given off from soda.

But there is one great objection to the use of soda alone as a
leavening agent. After baking soda has lost its carbon dioxide gas, it
is no longer baking soda, but is transformed into its relative,
washing soda, which has a disagreeable taste and is by no means
desirable for the stomach.

Man's knowledge of chemicals and their effect on each other has
enabled him to overcome this difficulty and, at the same time, to
retain the leavening effect of the baking soda.

211. Baking Powders. If some cooking soda is put into lemon juice or
vinegar, or any acid, bubbles of gas immediately form and escape from
the liquid. After the effervescence has ceased, a taste of the liquid
will show you that the lemon juice has lost its acid nature, and has
acquired in exchange a salty taste. Baking soda, when treated with an
acid, is transformed into carbon dioxide and a salt. The various
baking powders on the market to-day consist of baking soda and some
acid substance, which acts upon the soda, forces it to give up its
gas, and at the same time unites with the residue to form a harmless
salt.

Cream of tartar contains sufficient acid