# 27 CFR § 30.23 - Use of precision hydrometers and thermometers.

§ 30.23 Use of precision hydrometers and thermometers.

Example.
A hydrometer reads 192.85° at 72.10 °F. The correction factors for the hydrometer and the thermometer, respectively are minus0.03° and plus0.05°. The corrected reading, then, is 192.82° at 72.15 °F.
From Table 1: 193.0° at 72.0 °F. = 190.2° = 189.1° = 1.1° = 189.1° = 188.9° = 0.2°
The hydrometer difference (1.1°) multiplied by the fractional degree of the hydrometer reading (0.82°) = 0.902.

The temperature difference (0.2°) multiplied by the fractional degree of the temperature reading (0.15°) = 0.03°.

Proof at 60 °F. = 189.1 + 0.902 − 0.03 = 189.972° = 190.0°.
As shown, the final proof is rounded to the nearest tenth of a degree of proof. In such cases, if the hundredths decimal is less than five, it will be dropped; if it is five or over, a unit will be added.
(Sec. 201, Pub. L. 85-859, 72 Stat. 1358, as amended (26 U.S.C. 5204))
[T.D. ATF-198, 50 FR 8535, Mar. 1, 1985, as amended by T.D. ATF-381, 61 FR 37004, July 16, 1996]