388 FIELD AND GARDEN PRODUCTS 



acid odor to be dissipated. Upon delivery of the grain on the basis 

 of these samples, the odor of sulphurous acid is readily detected and 

 the buyer is dissatisfied because he believes the car of grain delivered 

 is not like the original sample. 



Method of Sulphur Bleaching. There are several types of grain 

 bleachers in use, the most common of which is the "tower" or "chim- 

 ney" bleacher, so called because of the style of its construction. The 

 different forms of this type vary principally in the manner of dis- 

 tributing the grain at the top and in the way in which it passes 

 through the bleacher. These tower bleachers are constructed of 

 brick, masonry, or wood covered with galvanized iron ; and for con- 

 venience in handling the grain through them the towers are built 

 close to the elevator, the top of the tower ussally corresponding with 

 the upper working floor of the elevator, which may be at a height 

 of 25 to 60 feet above the ground. On the interior of the bleaching 

 tower, which is about 3 or 4 feet square, are alternating series of de- 

 flecting shelves set at an angle of about 45 to the horizontal plane. 

 The purpose of these shelves is to retard the movement of the grain 

 and to distribute it evenly through the tower after it falls from the 

 spout at the top. 



As practiced commercially, sulphur is burned in a furnace or 

 oven located some distance from the bleaching tower as a precaution 

 against fire. The burning sulphur coming in contact with the oxy- 

 gen of the air forms sulphur-dioxid gas, which is forced into the 

 bleaching tower 8 or 10 feet from its base through a pipe leading 

 from the furnace. 



In order that the bleaching may be accomplished this sulphur- 

 dioxid gas must come in contact with water and unite with it, in 

 which case it forms sulphurous acid, which is the bleaching agent. 

 For this reason the grain, as it passes into the bleaching tower at the 

 top, is dampened with either a jet of steam or small sprays of water. 

 The sulphur-dioxid gas, circulating upward, unites with the moisture 

 adhering to the outside of the downward-moving grain, thereby 

 making the bleaching possible. 



The base of the tower bleacher forms a pocket in which the grain 

 is allowed to accumulate to a point underneath the inlet for the sul- 

 phur dioxid. Owing to the accumulation of the grain in this pocket, 

 better action of the sulphurous acid upon the stained and discolored 

 grain is afforded by lengthening the time it is confined in the 

 bleacher. With this method of bleaching, the grain is in the tower 

 about two or three minutes. 



After treatment in the bleaching tower the grain is returned to 

 the elevator bins, where it is customarily left from 24 to 48 hours, 

 and where a large part of the actual bleaching takes place. If one 

 bleaching fails to produce the desired result, the process is repeated. 



Before loading for shipment, the grain thus treated is "run" or 

 "handled" in the elevator for the purpose of cooling it and also to 

 remove the sulphurous-acid odor, which is only partly accomplished. 

 More or less moisture is lost during the handling, but the operator 

 aims to remove no more moisture than is necessary, because the addi- 



