A MOISTURE TESTER FOR GRAIN. 11 



temperature is reached extinguish the flame quickly, after which the 

 thermometer will show a slight gratlual im-rease in temperature. If 

 the sample contains a large percentage of moisture there is danger of 

 boiling over, but this can usually bo prevented by lowering the flame 

 whenever the action in the flask becomes too vigorous, as can be 

 readily determined through the mica window in the front of the com- 

 partment. As soon as the water stops dropping from the condenser 

 tube, which usually requires from four to six minutes after the flame 

 has been extinguished, the test is complete. However, before read- 

 ing the amount of moisture remove the covers and then disconnect 

 the flasks from the condenser tubes in order to allow the small quan- 

 tity of moisture which sometimes collects at the base of the No. 3 

 rubber stoppers to drop into the graduated measuring cylinders. 

 The percentage of moisture is read beneath the layer of oil on top of 

 the water, as shown in figure 3. In order to guard against possible 

 error it is desirable to make duplicate tests of all samples and take the 

 average of the two readings as the correct percentage of moisture. 



Wliile the contents of the flasks are still hot, take the flask by the 

 side tube and after giving a slight whirling motion invert quickly, 

 emptying the contents into a suitable strainer, so that the oil can be 

 recovered for further use. 



When the flasks are not in use, keep them in place in the compart- 

 ments and make all connections the same as for a test. In using a 

 new flask for the first time "run" a preliminary sample previous to 

 making a regular test, so that all the flasks will be in uniform con- 

 dition. 



HOW TO TEST DIFFERENT SUBSTANCES.a 



Detailed instructions have been worked out for making moisture 

 determinations of a limited number of substances, as follows: 



Barley. — Use 100 grams of grain and 150 cubic centimeters of oil, 

 and extinguish the flame when the thermometer registers 190° C. 



Corn (maize). — Use 100 grams of grain and 150 cubic centimeters of 

 oil, and extinguish the flame when the thermometer registers 190° C. 

 This method, however, can not be used with the pop corns. 



a Different substances are likely to require slightly different treatment, which can 

 be determined only by careful experiments covering a wide range of conditions, 

 checking the results wi th the tests made by drying a definite quantity to constant weight 

 and calculating the loss in weight as the percentage of moisture. The data here shown 

 were secured by checking the results with moisture determinations made by drying 

 to constant weight in the common type of double-walled oven filled with water main- 

 tained at the boiling point, except that the proper treatment for flaxseed was deter- 

 mined by checking with samples dried to constant weight in a 28-inch vacuum at a 

 temperature of 99° to 100° C. Moisture determinations made in vacuum at tempera- 

 tures of 105° or 108° C. will show higher percentages than will result from the method 

 herein described. 

 [Cir. 72] 



