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 one, two, three. The difference is an arbitrary one and not founded upon any chemical data but wholly upon the physical appearance, degree of moisture, and freedom from extraneous admixtures.

Wheat Products.—The principal product of wheat is flour. The milling process for wheat is highly interesting both from a chemical and technical point of view, but cannot be described in full in this manual. The old-fashioned milling of wheat, namely, pressing between stones and separation of the flour by bolting has been almost entirely superseded by the modern milling with metal rollers.

× 200.—(Courtesy of Bureau of Chemistry.)

Altogether nearly a hundred different products are made incident or final to the milling of wheat. Only those products, however, which are used for human food interest us at the present time.

Chief Varieties of Flour.—The highest grade of wheat flour is known usually by the term "patent"; a lower grade is known as "bakers' flour" and a third as low grade flour. A barrel of flour weighs 196 pounds and requires about 258 pounds of wheat for its manufacture. The whole product from the 258.35 pounds of wheat is shown in the appended table.

In general it may be said that about 75 percent of the weight of the wheat is obtained as merchantable flour of some kind, about 60 to 70 percent being