I

Tartaric acid, 3 parts; sodium bicarbonate, 1 part; starch, 0.75 part. Of this baking powder the required amount for 500 parts of flour is about 20 parts for rich cake, and 15 parts for lean cake.

The substances employed must be dry, each having been previously sifted by itself, so that no coarse pieces are present; the starch is mixed with the sodium bicarbonate before the acid is added. When large quantities are prepared the mixing is done by machine; smaller quantities are best mixed together in a spacious mortar, and then passed repeatedly through a sieve. Instead of starch, flour may be used, but starch is preferable, because it interferes with the action of the acid on the alkali.

II

A formula proposed by Cramp-ton, of the United States Department of Agriculture, as the result of an investigation of the leading baking powders of the market, is:

Potassium bitartrate.. . 2 parts Sodium bicarbonate... 1 part Cornstarch........... 1 part

The addition of the starch serves the double purpose of a " filler" to increase the weight of the powder and as a preservative. A mixture of the chemicals alone does not keep well.

The stability of the preparation is increased by drying each ingredient separately by exposure to a gentle heat, mixing at once, and immediately placing in bottles or cans and excluding access of air and consequently of moisture.

This is not a cheap powder; but it is the best that can be made, as to health-fulness.

III

Sodium acid phosphate ...........     20 parts

Calcium acid phosphate..........     20 parts

Sodium bicarbonate    25 parts

Starch............     35 parts

Caution as to drying the ingredients and keeping them dry must be observed. Even the mixing should be done in a room free from excessive humidity.

IV

Alum Baking Powder.—

Ammonium alum,

anhydrous...... 15 parts

Sodium bicarbonate 18 parts Cornstarch, q. s. to make 100 parts.

Mix. The available carbon dioxide yielded is 7.5 per cent or 8 per cent.