Hydrometers

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Hydrometers are used to measure densities of liquids. They consist of a glass tube with a pipe at the lower end. Pumping the flexible bulb at the top and then releasing it causes liquid to enter the hydrometer, and the glass float will float in the liquid, the density of which is to be measured. The Glass float is weighted with mercury or lead so that it floats upright, and has an upper stem, graduated to read the relative density of the liquid.

By varying the amount of lead shot or mercury, the hydrometer can be made to read a specific range of densities. Hydrometers are specially made for each density range. The acid in a bater has a rang of 1.25 – 1.30. A reading below 1.15 indicates recharging is necessary.