2 BULLETIN 725, U. S. DEPARTMENT OF AGRICULTURE. 
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 com- 
monly 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 Depart- 
ment of Agriculture regarding the sulphur bleaching of oats is given 
in Service and Regulatory Announcements Xos. 15 and 16 of the 
Bureau of Chemistry. 
METHOD OF BLEACHING OATS COMMERCIALLY. 
The method of bleaching oats and barley commercially is practi- 
cally the same throughout the country, with the occasional exception 
of a few changes hi the technique that have been made by the indi- 
vidual 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 gram, 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 in 
contact with the sulphur fumes. Fumes of burning sulphur are sul- 
phur dioxid (S0 2 ), which when combined with water form sulphu- 
rous acid (H 2 S0 3 ), S0 2 plus H 2 = H 2 S0 3 , an active bleaching agent. 
It can readily be seen that the addition of water in some form is neces- 
sary for the formation of sulphurous acid and an ultimate bleaching 
of the product. After the oats have passed through the bleaching 
tower, they are usually run into a bin and allowed to stand over night, 
when they are cooled or dried as necessity may require. In the event 
that any considerable amount of water has been added during the pro- 
cess, it is usuallv necessarv to drv out this excess moisture before the 
