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"A form of balance in which the weight of the body under examination is measured by the stretching (torsion) of an elastic wire in the form of a long spiral. A common use of the simple form of spiral balance is in determining the specific gravity of small fragments of minerals, which for this purpose are weighed first in the upper pan and then in that below, which is immersed in water." —Whitney, 1889

Spiral Balance

"A form of balance in which the weight of the body under examination is measured by the stretching (torsion)…

"Determines the specific gravity of any given liquid. A hollow ball, C, rises to a graduated scale while the solid ball, B, keeps C vertically positioned." —Quackenbos 1859

Hydrometer

"Determines the specific gravity of any given liquid. A hollow ball, C, rises to a graduated scale while…

A hydrometer of constant weight. This device measures the specific gravity of liquids. The specific gravity is the ratio of the density of the liquid to the density of the water

Hydrometer

A hydrometer of constant weight. This device measures the specific gravity of liquids. The specific…

A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water. A hydrometer is usually made of glass and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright. The liquid to be tested is poured into a tall jar, and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer is noted. Hydrometers usually contain a paper scale inside the stem, so that the specific gravity can be read directly.

Common Hydrometer

A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids;…