How to measure specific gravity of a liquid using a hydrometer

A hydrometer is used to measure the specific gravity of a liquid. Winemakers and saltwater aquarists often use hydrometers to determine whether they need to add sugar to their wine or salt to their fish tanks. A clean, distilled water sample has a specific gravity of 1.000. This is the measurement on which all other liquids are based. To read a hydrometer, look at the scale inside the hydrometer float. The scale on most models reads from 0.990 to 1.120.

Things You'll Need

• Sample flask
• Hydrometer
• Turkey baster

Instructions

1. Remove a sample of the liquid you wish to test with a turkey baster, and transfer it to the testing flask.

2. Place the testing flask on a flat, level surface.

3. Gently lower the hydrometer into the flask. If there are bubbles clinging to the hydrometer, flick it to knock them off. If this does not get rid of the bubbles, remove the hydrometer and lower it again. Bubbles throw off the hydrometer reading.

4. Move the hydrometer to the middle of the flask so it is floating freely and not attached to the sides.

5. Take the measurement at the lowest point of the curved surface of the liquid.

Tips & Warnings

• Specialty hydrometers are available for soil colloids, milk and battery acid.

References

• Grapestompers: How to Use a Hydrometer
• Lumcon.edu: Using a Hydrometer