Use a hydrometer to determine the specific gravity of a liquid. Find hydrometer types listed below, along with a step-by-step process for reading a hydrometer.
Plain Form. Because they don’t have a built-in thermometer, they use a separate thermometer to measure temperature
Combined Form. Includes a built-in thermometer in the body or stem to measure the sample’s temperature
Specific Gravity. The ratio of the density of a sample at 60°F (15.6°C) to the density of water at 60°F (15.6°C).
API scale. The standard scale for petroleum products as selected by the American Petroleum Institute (API), the United States Bureau of Mines, and the National Institute of Standards and Technology (NIST).
Baumé. Used for syrups and other liquids heavier than water.
Brix Scale. The choice of the sugar industry. The degrees of the scale are equal to the percentage of sucrose by weight at standard temperatures
Salt. Graduated in % saturation or % by weight of salt in solution
Alcohol (Tralle and Proof Scales). Measure directly in percentage ethyl alcohol by weight in water from 0 to 100%. The Proof scale indicates the proof of alcohol from 0 to 200 proof. Proof is twice the percentage of alcohol by volume in solution.
Soil. Determine the specific gravity of a suspension, enabling the percentage of particles of a certain equivalent particle diameter to be calculated.
Reading a Hydrometer
1. Pour your sample into a smooth, clear cylinder or jar that is dry or well rinsed with a portion of the sample
2. Ensure your sample is thoroughly mixed
3. Immerse the hydrometer in the liquid to a point slightly below the place where it naturally floats. Make sure the hydrometer and liquid are at rest and free of air bubbles
4. Measure the temperature of the sample. Ideally, the sample temperature should be equal to the temperature standard of the hydrometer, generally 60°F (15.6°C). If temperature differences are unavoidable, correction tables can help to adjust readings
5. Take your reading at the point where the surface of the liquid crosses the hydrometer
View our selection of hydrometers.
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