THE BROWN-DUVEL MOISTURE TESTER 
11 
for making moisture determinations of wheat, however, the flame 
should be extinguished when the thermometer reaches a temperature 
of 185° and not at 180° C, as is required when using glass flasks, 
otherwise the treatment should be the same. Correct temperatures for 
use with copper flasks in making moisture determinations of the other 
grains have not been determined. 
SPECIAL DOUBLE-WALLED DISTILLATION FLASK FOR TESTING FLOUR AND MEAL * 
A special double-walled flask designed for use in connection with 
the Brown-Duvel tester for making moisture determinations of flour 
and meal has the same outside dimensions as the regular distillation 
flask which is illustrated in Figure 8. The double-walled flask can 
G.3 C./77. 
(2%') 
M cm. 
(sfr) ■ 
frf*L 
o.G cm. 
Fig. 10. 
-Special double-walled distillation flask for testing moisture content in 
flour and meal 
be made of either 'glass or copper. It is illustrated in Figure 10. 
The inner flask has a capacity of approximately 900 cubic centimeters 
and the space between the two walls should hold not less than 250 
nor more than 300 cubic centimeters. 
If the flasks are made of copper, the thickness of the copper be- 
fore it is spun should be 0.022 inch, or 16 ounces to the square foot. 
The copper flasks will have to be made in two sections and the sec- 
tions soldered together in the middle with a very hard solder. The 
soft solder commonly used by plumbers is not suitable for this work. 
Success with these flasks has been attained only when they were 
soldered together with a silver solder. The neck of the flask must be 
3 This task was develop^ by J. H. Cox of the Grain Division, Bureau of Agricultural 
Economics. The flask and its manner of construction are fully described in Department 
Bulletin No. 56. 
