The Hydrometer

Hydrometer is an instrument for measuring the Density of a Liquids

Construction of hydrometer.

The construction of hydrometer is based on the facts that the depth to which a tube sinks in a liquid depends on(inversely proportional to)  the density of the liquid in which it is floating.

A simple hydrometer can be constructed by loading a small test-tube with some lead shots or small peddles so that it can float vertically in the liquid. A graduated scale can then be attached inside the tube to read the depth while it sinks in the liquid. You can calibrate the hydrometer by using water and paraffin oil with density and  Then workout a scale to measure other liquid density.

When this test tube is immersed ,

Volume of liquid displaced

If the cross-sectional area of the tube ,    the volume

     .

                         (ɤ=proportional to)

Practical hydrometer also work base on the principle that

The higher the density ρ of a liquid the less the hydrometer sinks (h) . in the liquid.

Application Of Practical Hydrometer.

Practical hydrometer is used as lactometer to test milk

It is also used to test the concentration of acid in batteries. The relative density of the acid should be 1.25 when fully charged and 1.15 when discharged. This is a better way to test battery than using voltmeter which gives sae reading every time.

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