A hydrometer measures the relative density (specific gravity) of a liquid by observing how high it floats in that liquid.
Here's a breakdown of the process:
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Preparation: Pour the liquid you want to test into a tall, clear container, such as a graduated cylinder. The container must be wide and deep enough for the hydrometer to float freely without touching the sides or bottom.
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Insertion: Gently lower the hydrometer into the liquid. Avoid dropping it, as this can damage the instrument. Release it carefully and allow it to float naturally.
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Reading: Once the hydrometer settles and is floating freely, observe the point where the surface of the liquid intersects the graduated scale on the stem of the hydrometer. This reading directly corresponds to the liquid's relative density (or specific gravity). The scale is usually pre-calibrated. Make sure your eye is level with the liquid surface to avoid parallax errors.
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Interpretation: The reading indicates the relative density of the liquid compared to water. A reading of 1.000 means the liquid has the same density as water. A reading greater than 1.000 indicates the liquid is denser than water, and a reading less than 1.000 indicates it is less dense.
Example:
If a hydrometer reads 1.040 in a sample, it means the liquid is 1.040 times denser than pure water. This is useful for things like measuring the sugar content in brewing, antifreeze concentration, or battery acid strength.
