18 BULLETIN 1375, U. S. DEPARTMENT OF AGRICULTURE 
exactly four-fifths immersed in the oil, as shown in Figure 2. Place 
the flask in the proper compartment of the tester and proceed in a 
similar manner with the remaining samples. 
The correct adjustment of the thermometer is a factor which must 
not be ignored. If the (mercury bulb of the thermometer is too near 
the bottom of the flask, the percentage of moisture will be too low : 
and if the mercury bulb is placed too high, the percentage of mois- 
ture will be too high. For the same reason it is important that there 
be uniformity in the length of the mercury bulbs of the thermom- 
eters, which, as previously stated, should be approximately three- 
fourths inch. 
As the thermometer is being inserted, glance along the side tube of 
the flask to make certain that it has not become stopped by the lodg- 
ment of some particle while the flask was being emptied or filled. 
If the side tube is not open to permit the free escape of the rapidly 
forming steam the pressure during the heating will become sufficient 
to blow out the stopper and thermometer or possibly to burst the 
flask. 
When the flasks have been filled and placed in the compartments of 
the tester, connect the side tubes of the flasks by means of the Xo. 3 
rubber stoppers with the thimbles of the glass condenser tubes which 
extend down through the cold-water tank, so that the moisture which 
is liberated from the grain or other substance will be condensed and 
then collected in the graduated cylinders beneath the tank. Figure 2 
shows the correct manner of adjusting the various parts of the 
apparatus. 
Place the cover over the flask, then ignite the gas, the heating 
capacity of which has already been adjusted, as described on page 
22. When the desired temperature is reached, extinguish the flame 
quickly, after which the thermometer will show a slight gradual 
increase in temperature, approximately 5 to 6°. Let the thermometer 
recede to 160° C. before making a reading. Before reading, remove 
the covers and then disconnect the flasks from the condenser tubes 
to allow the small quantity of moisture which sometimes collects at 
the base of the Xo. 3 rubber stoppers to drop into the graduated 
measuring cylinders. The percentage of moisture which has collected 
in the graduates is read beneath the layer of oil on top of the water. 
To guard against possible error, it is desirable to make duplicate 
tests of all samples, and if there is no appreciable variation, to take 
the average of the two readings as the correct percentage of moisture. 
While the contents of the flasks are still hot, remove the ther- 
mometer, take the flask by the side tube and after giving a slight 
whirling motion, invert quickly, emptying the contents into a suit- 
able strainer", so that the oil can be recovered for further use. 
When the flasks are not in use, keep them in place in the com- 
partments and make all connections the same as for a test. In using 
a new flask for the first time, or when the machine has been idle over 
24 hours, " run " a preliminary sample previous to making a regular 
test so that all the flasks will be in uniform condition. 
HOW TO TEST DIFFERENT SUBSTANCES 
Detailed instructions have been worked out for making moisture 
determinations of a limited number of substances, as follows : 
