ening the concrete of the foundation and tamping the concrete of the curb, to insure that the curb will be firmly bonded to the base. The concrete shall be well tamped and spaded along the forms, so that when they are removed there will be no open and porous places on the sides of the curb. The top surface of the curb shall be floated or troweled to a smooth finish. The forms for the curb shall be smooth, clean, free from warp, and of sufficient strength to resist springing out of shape. They shall be well staked and braced, and the top edges shall be at the same height and set true to line. To protect the curb from drying out too rapidly it shall, within 12 hours after it is placed be covered with gunny cloth, which shall be kept wet for five days.

SEPARATE CONCRETE CURBS.

Where the plans call for concrete curbs separate from the foundation they shall be constructed before the subgrade is finally completed and shall have the cross section shown on the plans. Such curbs shall be constructed in sections not less than 6 feet and not more than 12 feet in length and shall be true to grade and alignment.

The specification already given for concrete curbs constructed in combination with the foundation shall also apply to curbs constructed separate from the foundation as regards proportioning, mixing, and placing the concrete, constructing the forms, and all other features of construction which are not covered on the plans or in this specification.

STONE CURBS.

Where stone curbs are required, they shall be hauled and set before the subgrade is finally completed. The curbs shall be set to line and grade and shall be securely bedded in broken stone, gravel, or firm earth. In preparing the trenches for the curbs great care shall be exercised to see the material upon which the curb is to be set is well compacted, firm, and hard.

Stone curbing shall be quarried from hard, tough, homogeneous stone. The individual blocks shall have the cross section shown on the plans and shall be not less than 4 feet in length. Each block shall be free from seams and all other imperfections and shall be neatly dressed and finished on all exposed faces.

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UNITED STATES DEPARTMENT OF AGRICULTURE

BULLETIN No. 725

Contribution from the Bureau of Markets
CHARLES J. BRAND, Chief

October 22, 1918

Washington, D. C.

RSITY

A PRELIMINARY STUDY OF THE BLEACHING OF OATS WITH SULPHUR DIOXID.1

By GEORGE H. BASTON, Assistant Grain Supervisor.

LEACHING OATS with sulphur dioxid is a practice that has caused a great deal of controversy and discussion during the past few years. During the past score of years the commercial bleaching of oats and barley has greatly increased until, at the present time, this process is carried on to a considerable extent in nearly all of our larger oat-producing sections, the fundamental object being to improve the appearance of the product which is to be placed upon the market, and it was with a view to ascertaining the merits of this practice that these investigations were undertaken.

The character of the seasons in which oats are grown, and particularly the weather conditions prevailing at harvest time, have an influence upon their quality, condition, and appearance and deter

1 Other publications pertaining to this subject are:

Circular 40, Bureau of Plant Industry, U. S. Department of Agriculture: "A Simple Method of Detecting Sulphured Barley and Oats," by W. P. Carroll.

Circular 74, Bureau of Plant Industry, U. S. Department of Agriculture: "The Sulphur Bleaching of Commercial Oats and Barley," by LeRoy M. Smith.

Reprint from Circular 111, Bureau of Plant Industry, U. S. Department of Agriculture; "Improved Apparatus for Detecting Sulphured Grain," by George H. Baston.

Food Inspection Decision 145, Bureau of Chemistry, U. S. Department of Agriculture: "Bleached Oats and Barley".

Service and Regulatory Announcements 15, Bureau of Chemistry, U. S. Department of Agriculture: "Oats Bleached with Sulphur."

Service and Regulatory Announcements 16, Bureau of Chemistry, U. S. Department of Agricultur: "Oats Bleached with SO, and Oats Containing Added Barley."

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mine quite largely the manner in which they are subsequently handled. Oats grown and harvested in a dry season are usually sufficiently bright and bleaching is not necessary to give them a good salable appearance. It is only upon oats which are harvested in a wet season that sulphur bleaching is practiced to any considerable extent, although a certain percentage of the lower grades of oats of all crops have been bleached during the past several years.

These investigations were begun in 1915, and it is deemed advisable to present at this time the data in reference to the methods most commonly used, the results obtained by these methods, and the effects of bleaching on the grain itself. Many phases of the problem have not been investigated as yet, or sufficient data has not been obtained to justify their publication at this time. The attitude of the Department of Agriculture regarding the sulphur bleaching of oats is given in Service and Regulatory Announcements Nos. 15 and 16 of the Bureau of Chemistry.

METHOD OF BLEACHING OATS COMMERCIALLY.

The method of bleaching oats and barley commercially is practically the same throughout the country, with the occasional exception of a few changes in the technique that have been made by the individual operator, either better to adapt the process to his peculiar needs, or to give him what he considers a product of better quality. Two methods generally are in use, and these methods are practiced interchangeably by individual operators. These two processes are known as the cold process and the warm process, the only difference being that in one case steam is used to moisten the grain, and in the other cold water is used. The apparatus consists of a tower which is constructed of wood or concrete, an oven for burning the sulphur, a cooling chamber, a suction fan for drawing the fumes from the cooling chamber to the tower, where they are brought in contact with the oats, and a jet for injecting steam or water as the oats enter the tower. Fumes resulting from burning sulphur are drawn up through the moist grain while at the same time the grain runs from the top of the tower to the bottom, bringing as nearly as possible every kernel i contact with the sulphur fumes. Fumes of burning sulphur are sulphur dioxid (SO2), which when combined with water form sulphu rous acid (H2SO), SO, plus H2O=H2SO,, an active bleaching ager It can readily be seen that the addition of water in some form is nece sary for the formation of sulphurous acid and an ultimate bleachir. of the product. After the oats have passed through the bleachi tower, they are usually run into a bin and allowed to stand over nig when they are cooled or dried as necessity may require. In the eve that any considerable amount of water has been added during the p cess, it is usually necessary to dry out this excess moisture before

grain can be shipped with safety. Some operators prefer to add as little moisture as possible, in which case the product merely requires cooling before shipment. Others maintain that they get a better-appearing product by adding considerable moisture, and then drying out the excess before shipment.

The bleaching of oats and barley as practiced at the present time is a continuous process after the apparatus has once been set in motion, and very little attention is required except to see that the proper supply of sulphur is kept in the furnace, the proper amount of water is added, and that the grain is kept at a uniform flow. Some of the largest and most efficient bleaching plants have capacities of 2,000 bushels of grain per hour.

Photographs of sulphur-bleaching apparatus are shown in figures 1, 2, and 3, which illustrate some of the leading types of commercial bleachers.

CHARACTER OF INVESTIGATIONS.

In the fall of 1915, samples of oats were collected from representative sections in which the commercial bleaching of oats is practiced to a considerable extent, and these samples were carefully examined and analyzed. The analyses of samples from the same lots of grain before and after bleaching were compared. Using these data as a basis for further investigations, additional experiments were undertaken. Visits were made. to some of the most important elevators throughout the Middle West that operate bleachers. Samples of as many different grades and qualities of oats as possible were obtained and studied. These were bleached by the regular process in vogue at the elerator, and also by modifications of this method which suggested hemselves to the writer or were suggested by the operator of the levator. Careful attention was paid to the amount of water bsorbed, the atmospheric conditions, and the condition and ppearance of the oats before and after bleaching. An endeavor ́as made at all times to improve if possible the appearance of the nal product.

Each different grade or quality was carefully studied before and ter treatment, and as many types of damaged oats as possible ere obtained and examined. The effect of bleaching on each kind

of damaged grain, such as weather stained, heat damaged, bin burned, and ground damaged, was carefully noted. This same line of experimentation was carried on at several representative points in order to

FIG. 2.-A grain bleaching apparatus with square tower. This type is in very common use throughout the Middle West.

get the benefit of varying conditions. Acknowledgment of appreciation is made for the assistance and cooperation given by the owners and operators of the elevators where experiments were conducted.