THE BROWN-DUVEL MOISTURE TESTER 5 
The center of gas line should be 3% inches from front of base. 
The gas pipe should be three-fourths inch inside diameter. 
Pet cocks for gas burners are mounted on pipe line, the center of 
which coincides with centers of compartments. 
Figure 3 is a working drawing of the Brown-Duvel tester, 
equipped with gas heaters. 
DESCRIPTION OF ACCESSORIES 
THERMOMETERS 
It is of the utmost importance that the thermometers be of extra 
quality and not the ordinary grade of chemical thermometers which 
are commonly furnished with apparatus of this general character. 
The success of this method of making moisture determinations de- 
pends largely upon the accuracy with which the temperature read- 
ings are made, and any thermometer showing an error of more than 
one-half of a degree at any of the prescribed points should not be used 
unless such errors are known and provided for in the readings. 
It is also necessary that the mercury bulbs of each of the ther- 
mometers be of approximately the same length, so that uniformity 
can be had as to the depth to which the thermometers are immersed 
in the oil, the correct depth being four-fifths immersion, as shown 
in Figure 2. 
The thermometer used in this apparatus should be made of suitable 
glass properly annealed for use at high temperatures, and should be 
free from defects which would prevent making accurate readings. 
The graduations of the thermometer should be in whole degrees 
from 0° to 220° C, and it should have a white background on the 
stem. Errors in scale graduations should not exceed 1° at any point 
and between 170° and 200° C. should not exceed 0.5°. The diameter 
of the stem of the thermometer should be nine thirty-seconds inch, 
so that it will properly fit into a No. 5 one-hole rubber stopper. The 
length of the mercury bulb should be approximately three-fourths 
inch (19 mm.) and its diameter should be approximately 5 milli- 
meters. 
Variation from the dimensions given above and pictured in Figure 
4 should be not greater than 0.25 millimeter on the stem and 
bulb diameters and one-sixteenth inch (1.6 mm.) in the bulb length. 
Manufacturers should be required to furnish certificates of cor- 
rection with all thermometers showing errors in calibration and 
graduation exceeding 0.5° at 175° and 200° C. 
A standard thermometer for use in the Brown-Duvel moisture 
tester is illustrated in Figure 4. 
GRADUATED MEASURING CYLINDERS 
The full-sized graduated cylinders for measuring the moisture 
content of the grain being tested should have a capacity of 25 cubic 
centimeters. 
The graduates should be made to contain the indicated volume at 
20° C, and the graduations in whole cubic centimeters and either 
one-tenth or two-tenths of a cubic centimeter should be legible and 
conspicuously and permanently marked on one side of the graduate. 
