14 



BULLETIN 927, U. S. DEPARTMENT OF AGRICULTURE. 



so slight that the extra handling would be unprofitable. However, 

 such treatment seems to be necessary in order to make the subsequent 

 drying by the rotary drier successful. If the seed contains more than 

 52 to 55 per cent of moisture, it has a tendency to pack and stick to 

 the walls of the drier instead of drying and discharging freely. In 

 the experiments conducted none of the expeller or centrifuged seed 

 packed in the drier, but in every case the untreated seed did pack. 



An experimental direct-heat drier (fig. 8) was installed for the 

 work, the heat being supplied by gas. The seed-drying chamber of 

 this machine was 5 feet long by 1 foot in diameter and rotated at 



Fig. 8. — An experimental direct-heat drier. 



the rate of 16 revolutions per minute. About six or seven minutes 

 were required for the seed to pass through the machine. Inasmuch 

 as this period was too short for complete drying, several passages 

 through the drier were necessary. Trials on a semicommercial scale 

 demonstrated that such a machine is readily adapted to the drying 

 of such material as washed tomato seed, since it is easily controlled, is 

 continuous in operation, and carries a minimum labor charge because 

 it requires but little attention. 



In order to produce seed of proper dryness it was necessary to 

 pass it through the machine three times. The moisture content, 

 whirl) at the beginning was 52.4 per cent, at the end of each passage 



