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8.R.A.-A.M.S. 147 Revise4 rch 1959
United States Department of Agricult ri 4
AGRICULTURAL MARKETING SERVICE '
SERVICE AND REGULATORY ANNOUNCEMENTS NO. 1 1'
METHODS FOR DETERMINING MOISTURE CONTENT AS
SPECIFIED IN THE OFFICIAL GRAIN STANDARDS OF
THE UNITED STATES AND IN THE UNITED STATES
STANDARDS FOR BEANS, PEAS, LENTILS, AND RICE 2
The use of airtight containers to protect the samples of grain and other
commodities from losing or gaining moisture before the moisture test is made,
and the careful handling of the samples is necessary if the moisture test results
are to be authentic. Samples that are to be tested for moisture content should
not be unduly exposed to the air before grinding (if grinding is required) ; and
it is even more important that any ground material be properly protected to
prevent any change in moisture content. When samples of these commodities
have been thoroughly dried, they are extremely hygroscopic, even at 130 C.
Therefore moisture dishes must be covered and desiccated immediately upon
removal from the oven.
In making moisture determinations an analytical balance should be used and
all weighing should be made to the nearest 0.1 mg.
Moisture dishes.-Moisture dishes should be made of heavy gage aluminum
so that they will not dent readily. They should have a diameter of about 55
mm., a height of about 15 mm. with slightly tapered sides and be provided with
tightly fitting slip-in covers which are designed to fit snugly under the dishes
when they are placed in the oven. Both the dish and its cover should be identi-
fied by the same number. (Moisture Dishes, Special, Precision, No. 1631, are
available from Fisher Scientific Co.)8 Before using a moisture dish, it should
be dried for 1 hr. at 1300 C. or by an equivalent drying procedure, cooled in a
desiccator, and the tare weight obtained.
Desiccator.-Desiccator should be airtight and should contain activated alu-
mina, "Molecular Sieves" (a product of Linde Air Products Co.),8 or other
equally suitable desiccant. Reignited quicklime, silica gel, and anhydrous cal-
cium chloride are not suitable desiccants.
Oven.--Oven may be of gravity-convection or mechanical-convection (forced
draft) type. It should be well insulated and maintain a reasonably uniform
temperature throughout the chamber and be capable of being maintained at the
desired temperature at the shelf level of the samples. The oven should be
properly ventilated and equipped with a suitable thermometer accurate to
within 0.5 C., and with removable perforated or wire shelves.
Mill.--The mill should be of a type that is capable of grinding the sample
without undue exposure to the atmosphere and without appreciable heating,
so as to avoid possible gain or loss of moisture. (Wiley Laboratory Mill, In-
termediate Model is satisfactory for this purpose.)
1 This announcement was originally issued as Service and Regulatory Announcements
No. 147 of the Bureau of Agricultural Economics.
a a. Official Grain Standards of the United States. SRA-AMS-177.
b. United States Standards for Beans. 7 CFR, 68.101-103.
c. United States Standards for Dry Peas. 7 CFR, 68.401-403.
d. United States Standards for Split Peas. 7 CFR, 68.501-503.
e. United States Standards for Lentils. 7 CFR, 68.601-603.
f. United States Standards for Rough Rice, Brown Rice, and Milled Rice. 7 CFR,
68.201-203, 68.251-253, and 68.301-303.
The mention of firm names or trade products does not imply that they are endorsed
or recommended hy thep 1pa nar+mnt # Ac ti-r 'n other firms or similar products not
mentioned. UNIV. OF FL LU.
498621- 9 DOuLMENT DEPTL
AIR-OVEN (130 C.) METHOD FOR WHEAT, BARLEY, OATS, RYE, GRAIN
SORGHUMS, SOYBEANS, PEAS, LENTILS, AND RICE
DETERMINATION A (one-stage procedure) 4
Grind a representative 10- to 15-gm. portion of the original sample so that
all the ground material will pass through an 18-mesh wire sieve. Certain types
of mills heat the sample during grinding, and such mills should not be used
unless the mill is permitted to cool between grindings. The ground sample
should pass directly from the mill into a suitable container not much larger
than necessary to hold the sample.
Immediately after grinding, place representative portions (duplicates at least)
of approximately 2 to 3 gn. each of the ground, well-mixed sample into tared
moisture dishes. Immediately cover the dishes containing the portions of the
samples and weigh. Subtract the weight of each dish from the total weight
and record the result as the weight of the sample. Uncover the dishes and
place them with covers beneath in the oven reiulaitedl to 1301 (C. All mois-
ture dishes should be placed on a single shelf in the oven with the bulb of the
oven thermometer on the same level and as close as ipo-.;ille to the dishes.
After heating the material for 1 hour (timing the interval from the time when
the oven reaches 130 C. after the insertion of the dishes), remove the shelf
containing the dishes, cover the dishes immediately and transfer them to a
desiccator. Weigh the dishes when they reach room temperature. Determine
the loss in weight as moisture. Calculate the percentage of moisture by divid-
ing the loss in weight due to heating by the weight of the original sample and
multiplying by 100. Replicate determinations should check within 0.2 percent
DETERMINATION B (two-stage procedure)
Fill two or more tared moisture dishes nearly full with representative por-
tions of the unground sample, the moisture content of which is to be deter-
mined. Weigh each covered dish including its contents. Subtract the weight
of the dish from the total weight and record the result as the weight of the
Uncover the dishes and place them with covers beneath in a warm, well-ven-
tilated place (preferably on top of the heated oven) so that the sample will
dry reasonably fast and reach approximately an air-dry condition. This usually
may be accomplished in from 14 to 16 hours when the top of the heated oven is
used for this preliminary drying. In all cases, except for soybeans, the moisture
content must be reduced to 16 percent or less (10 percent in the case of soy-
beans) in this first stage.
Cover the metal dishes containing the air-dried samples and weigh each of
them soon after they reach room temperature. Determine the loss in weight
of the sample and record it as the moisture loss that is due to air drying.
Using the air-dried sample, proceed in the manner described under Determina-
This procedure may be used on all samples believed to contain 16 percent or less of
moisture. If, after oven trials, the sample shows more than 16 percent of moisture, the
two-stage procedure described under Determination B must be followed. In the case of
soybeans, all samples having more than 10 percent of moisture should be tested by the
Calculate the percentage of moisture in the original sample according to the
method indicated in the following example:
1. Weight of the portion of the original sample used for the
test (A) -- ------------------------------------ 27.2358 gm.
2. Weight of the portion after air drying (B) ------------- 25.1836 gm.
3. Moisture loss due to air drying () -------------------- 2.0522 gm.
4. Weight of the subportion of the air-dried sample used for
the 1300 C. air-oven drying (D) ----------------------- 2.8753 gm.
5. Loss of moisture due to oven drying (E) __--------------- .2974 gm.
6. Calculate the moisture content by substitution in the equa-
% moisture= X 100
0.2974 X 25.1836
% moisture= 27.2358 X100=17.10%
Replicate determinations should check within 0.2 percent moisture.
AIR-OVEN (1030 C.) METHOD FOR CORN AND BEANS
Place approximately 15 gm. of a representative portion of the unground sam-
ple in each of two or more tared moisture dishes. Weigh the covered dishes
and contents. Subtract the weight of each dish from the total weight and
record the result as the weight of the sample.
Uncover the dishes and place them with covers beneath for 72 hrs. in the
oven regulated at 1030i-1 C. The dishes should be placed on a single shelf
with the bulb of the oven thermometer as close as possible to them. At the
end of the heating period, remove the shelf containing the dishes, cover the
dishes immediately and place them in a desiccator. Weigh the dishes when they
reach room temperature. Determine the loss in weight as moisture and calcu-
late the percentage of moisture by dividing the loss in weight due to heating
by the weight of the original sample and multiplying by 100. Replicate deter-
minations should check within 0.2 percent moisture.
AIR-OVEN (1030 C.) METHOD FOR FLAXSEED
Place 5-7 gm. of a representative portion of the flaxseed into each of two
or more tared moisture dishes. Weigh the covered dishes and contents. Sub-
tract the weight of each dish from the total weight and record the result as
the weight of the sample.
Uncover the dishes and place them with covers beneath for 4 hrs. in the oven
regulated at 10301 C. The dishes should be placed on a single shelf with
the bulb of the oven thermometer as close as possible to them. At the end of
the heating period, remove the shelf containing the dishes, cover the dishes
immediately and place them in a desiccator. Weigh the dishes when they reach
room temperature. Determine the loss in weight as moisture and calculate the
percentage of moisture by dividing the loss in weight due to heating by the
weight of the original sample and multiplying by 100. Replicate determina-
tions should check within 0.2 percent moisture.
U. S. GOVERNMENT PRINTING OFFICE: 1959
UNIVERSITY OF FLORIDA
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