FED-STD-228A
Method 8322.1
18 APRIL 2014
SPECIFIC GRAVITY; HYDROSTATIC
1. SCOPE
1.1 This method is intended for use in determining the specific gravity of rubber insulating compounds
and sheaths. It is applicable to all compounds where the specimen is in one piece. It is much faster than
method 8321 but is not considered as accurate.
2. SPECIMEN
2.1 The specimen should consist of approximately 1 gram of the insulation or sheath taken from the
inspection unit.
3. APPARATUS AND REAGENTS
3.1 The apparatus and reagents shall be as follows:
3.1.1 An analytical balance and weights.
3.1.2 A fine wire approximately 0.004 inch in diameter for supporting the specimen.
3.1.3 Ninety-five percent ethyl alcohol.
3.1.4 Distilled water.
4. PROCEDURE
4.1 Unless otherwise specified in the detail specification, the temperature of the water during the test
shall be 25° ± 0.5°C (77° ± 1°F) unless the coefficient of expansion of the material is known, in which
case the determination may be made at any temperature and the value corrected to 25°C.
4.2 The specimen shall be weighed in the air and the value recorded as W1.
4.3 The wire for suspending the specimen shall be attached to one arm of the balance, weighed in water
and the value recorded as W2 noting the depth to which the wire was immersed.
4.4 The specimen shall be dipped in alcohol and blotted dry to eliminate the formation of air bubbles
when immersed in water. The specimen shall be attached to the wire, immersed in water, weighed, and
the value recorded as W3. The second weighing shall be made with the wire immersed in the water to
the same depth as previously without the specimen attached.
4.5 All weighings shall be made to the nearest milligram.
5. RESULTS
5.1 Calculations. The specific gravity of the specimen at 25/4°C shall be calculated as follows:
Specific gravity (25/4°C) = ____W1___ x 0.9971
W1-(W3-W2)
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