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 begim 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 Kegulatory Announcements Nos. 15 and 16 of the 

 Bureau of Chemistry. 



METHOD OF BLEACHING OATS COMMERCIALLY. 



The method of bleaching oats and barley conomercially is practi- 

 cally the same throughout the country, with the occasional exception 

 of a few changes in 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 differ ence 

 being that in one case steam is used to moisten the grain, and ii 

 other cold water is used. The apparatus consists of a tower whw 

 constructed of wood or concrete, an oven for burning the sulphi 

 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 dra\vn up through the 

 moist grain while at the same time the grain rmis 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 (SO2), which when combined with water form sulphu- 

 rous acid (H2SO3), SO2 plus H20 = H2S03, 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- 

 c^, it is usually necessary to dry out this excess njoisture before th^ 



irence 



iiui^; 



