A MOISTURE TESTER FOR GRAIN. 9 



RUBBER STOPPERS. 



The No. 5, one-hole, rubber stoj)pers which carry the thermometers 

 and the No. 3, one-hole, rubber stoppers used on the side tubes of the 

 flasks should be of such quality as will withstand comparatively 

 high temperatures and resist the action of the oil. Stoppers con- 

 taining a large percentage of pure gum are not desirable. They soon 

 swell and become uniit for use. Before attempting to put any of the 

 glass parts through the holes in the rubber stoppers they should be 

 moistened \vith oil or water, thereby lessoning the chances of breaking 

 the tubes and cutting the hantls. 



GENERAL DESCRIPTION OF THE METHOD. 



The method consists in heating whole grains, seeds, spices, or other 

 sunilar substances in a mineral oil having a flashing point much 

 above the boihng point of water, in condensing the water which 

 distills off, and in collecting and measuring it in a suitable graduate. 

 The method, as already stated, is so simple that the tests can be 

 made by any careful worker who is able to follow simple instructions. 



A single moisture determination can be made in twenty-live or 

 thirty minutes, and \vdth a 6-compartment tester, as shown in figure 

 1, six tests can be made in approximately the same time. In com- 

 mercial work, where a large number of tests are to be made, one man 

 and a helper, with the use of three 6-compartment machines, can 

 readily make 200 or more tests in a day of eight hours, an average 

 of less than two and one-half minutes for each test. In addition to 

 the rapidity with which moisture determinations can be made by 

 this method, it is especially valuable in testing substances which 

 have a large percentage of water, are diflicult to grind, or contain 

 such large quantities of volatile oils that determinations based upon 

 differences in weight during drying are unreliable. This method 

 also obviates the grinding of samples, thus eliminating the loss of 

 water which accompanies the grintling of material of relatively high 

 moisture content. Moreover, ground material has a tendency to 

 "cake" in the flask; consequently, this method is not entirely satis- 

 factory for making moisture determinations of flour, meal, powders, 

 or other similar substances, without some further modification. 



HOW TO MAKE A TEST. 



After properly mixing the bulk sample, carefully weigh the desired 

 quantity for the moisture test and empty immediately into the 

 distillation flask, to which add the oil and shake, with a slight whirl- 

 ing motion, until the two become well mixed. Grasp the neck of the 

 flask in one hand and hold it in such a manner that when the No. 5 



[Cir. 72] 



