How do you read a hydrometer?


Quick Answer

To read a hydrometer, drop it into the liquid sample you are testing, with the larger bulb going in first. Make sure the cylinder is not touching either side of the container holding the sample. Find the mark closest to the plane of the water.

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Full Answer

  1. Put the sample into the testing container

    Pour the sample liquid that you are comparing to water, with regard to specific gravity, into the container for testing. Leave enough room at the top of the container so that you can insert the hydrometer without pushing the water up over the top of the container.

  2. Insert the hydrometer

    Slide the hydrometer into the testing container, with the larger end down. Let the hydrometer bob in the water and find its own point of balance in the water. Keep the hydrometer from coming into contact with the sides of the testing container.

  3. Read the scale on the side of the hydrometer

    Wait until the hydrometer stops bobbing up and down, and find the line on the scale that is even with the plane of the water. Ignore the water along the meniscus, which looks like a small waterfall on the sides of the hydrometer. Do not read the highest point of the water on the neck, but instead read the line that follows the plane along the top of the water. Clean the hydrometer when you have finished.

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