572 THE SMALL GRAINS 



ing, and causes it to be more readily eaten by insects. 

 The percentage of moisture that an average sample of 

 grain should contain, however, varies greatly according 

 to locality and season. There is also a considerable 

 varietal difference. 



Harris and Thomas (1914) studied the change in weight 

 of grain during storage in Utah, which means really the 

 change in percentage of moisture. They found that 

 wheat and oats weigh most at thrashing time in that 

 region, but gain weight in the winter, and lose weight in 

 the summer. During the fall, just after harvest, there 

 is a gain in weight of 2^ to 4| per cent. 



631. Testing the moisture. Apparently the best 

 method of determining moisture content of grain is that 

 devised by Brown and Duvel (Duvel, 1910). The ker- 

 nels of the sample are heated in a mineral oil having a 

 flashing point much above the boiling point of water. 

 The water in the sample therefore distills over, and on 

 passing through a tube surrounded with cold water, is 

 recondensed and collects in a suitable graduate, and the 

 quantity in the sample is thus measured. An accurate 

 thermometer is kept with its bulb immersed always to 

 the same depth in the heated oil. 



In testing wheat, 100 grams of grain are used with 150 cc. of oil, 

 and the flame of the burner is extinguished when the thermometer 

 registers 180 C. In testing rye and barley the same amount of 

 grain and the same quantity of oil are used, and the flame is ex- 

 tinguished in the case of rye when the thermometer registers 175 C., 

 and in the case of barley when it registers 190 C. In testing oats 

 50 grams of grain and 150 cc. of oil are used, and the flame is ex- 

 tinguished when the thermometer registers 195 C. 



The apparatus has 6 compartments, so tests of 6 samples 

 can be made at one time. One man and a helper, with 



