The Fahrenheit hydrometer is a device used to measure the

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

of a liquid. It was invented by

Daniel Gabriel Fahrenheit Daniel Gabriel Fahrenheit FRS (; ; 24 May 1686 – 16 September 1736) was a physicist, inventor, and scientific instrument maker. Born in Poland to a family of German extraction, he later moved to the Dutch Republic at age 15, where he spen ...

(1686–1736), better known for his work in

thermometry Temperature measurement (also known as thermometry) describes the process of measuring a current local temperature for immediate or later evaluation. Datasets consisting of repeated standardized measurements can be used to assess temperature tren ...

Operation

The Fahrenheit hydrometer is a constant-volume device that will float in water. In the figure shown here, the hydrometer is floating vertically in a cylinder containing a liquid. At the bottom of the hydrometer is a weighted bulb and at the top is a pan for small weights. To use the hydrometer, one first accurately determines its weight (W) while it is dry. Next, the device is placed in water, and a weight (w) sufficient to sink a marked point on the rod to the water-line is placed on the pan. At that point, the weight of water displaced by the instrument equals W + w. The hydrometer is then removed, wiped dry, and placed in the liquid whose density is to be determined. A weight (x) sufficient to sink the hydrometer to the same marked point is placed in the pan. The density (D) of the second liquid is then given by D = (W + x) / (W + w).See page 170 of
School Physics
' by Elroy McKendree Avery, 1895, American Book Company, New York, from which much of this article is taken. The Fahrenheit hydrometer can be made of either glass or metal. The

Nicholson hydrometer Nicholson may refer to: People *Nicholson (name), a surname, and a list of people with the name Places Australia * Nicholson, Victoria * Nicholson, Queensland * Nicholson County, New South Wales * Nicholson River (disambiguation) * Nicholson Ro ...

is similar in design, but instead of a weighted bulb at the bottom there is a small container ("basket") into which a sample can be placed.

References

{{reflist Measuring instruments Dutch inventions

Operation

See also

References