Even when in their purest state, these chemicals are not harmless, as is so generally believed.  It is a very prevalent idea that when soda is neutralized by an acid, both chemical compounds are in some way destroyed or vaporized in the process, and in some occult manner escape from the bread during the process of baking.  This is altogether an error.  The alkali and acid neutralize each other chemically, but they do not destroy each other.  Their union forms a salt, exactly the same as the Rochelle salts of medicine, a mild purgative, and if we could collected from the bread and weigh or measure it, we would find nearly as much of it as there was of the baking powder in the first place.  If two teaspoonfuls of baking powder to the quart of flour be used, we have remaining in the bread made with that amount of flour 165 grains of crystallized Rochelle salts, or 45 grains more than this to be found in a Seidlitz powder.  It may be sometimes useful to take a dose of salts, but the daily consumption of such chemical substances in bread can hardly be considered compatible with the conditions necessary for the maintenance of health.  These chemical substances are unusable by the system, and must all be removed by the liver and excretory organs, thus imposing upon them an extra and unnecessary burden.  It has also been determined by scientific experimentation that the chemicals found in baking powders in bread retard digestion.

These substances are, fortunately, not needed for the production of good light bread.  The purpose of their use is the production of a gas; but air is a gas much more economical and abundant than carbonic-acid gas, and which, when introduced into bread and subjected to heat, has the property of expanding, and in doing, puffing up the bread and making it light.  Bread made light with air is vastly superior to that compounded with soda or baking powder, in point of healthfulness, and when well prepared, will equal it in lightness and palatableness.  The only difficulty lies in catching and holding the air until it has accomplished the desired results.  But a thorough understanding of the necessary conditions and a little practice will soon enable one to attain sufficient skill in this direction to secure most satisfactory results.

[Illustration:  Gem Irons]

GENERAL DIRECTIONS.—­All materials used for making aerated bread should be of the very best quality.  Poor flour will not produce good bread by this or by any other process.  Aerated breads are of two kinds:  those baked while in the form of a batter, and such as are made into a dough before baking.

[Illustration:  Perforated Sheet Iron Pan for Rolls.]