Hydrometer

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Hydrometer

A hydrometer is an instrument used to measure the specific gravity

Specific gravity

Specific gravity is defined as the ratio of the density of a given solid or liquid substance to the density of water at a specific temperature and pressure, typically at 4?C and , making it a dimensionless quantity ....
(or relative density

Relative density

Relative density, sometimes called specific density, is the ratio of the density of a substance to the density of a given reference material....
) of liquid

Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
s; that is, the ratio of the density of the liquid to the density of water.

A hydrometer is usually made of glass

Glass

Glass generally refers to a Hardness, brittle, transparency amorphous solid, such as that used for windows, many Glass Bottles, or eyewear, including, but not limited to, soda-lime glass, borosilicate glass, acrylic glass, sugar glass, Muscovite , or aluminium oxynitride....
and consists of a cylindrical stem and a bulb weighted with mercury

Mercury (element)

Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....
or lead shot

Lead shot

Lead shot is a collective term for small balls of lead. It is used primarily as projectiles in shotguns, but is also used for a variety of other purposes....
to make it float upright.

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Encyclopedia

A hydrometer is an instrument used to measure the specific gravity

Specific gravity

Relative density

Relative density, sometimes called specific density, is the ratio of the density of a substance to the density of a given reference material....
) of liquid

Liquid

Glass

Mercury (element)

Lead shot

Lead shot is a collective term for small balls of lead. It is used primarily as projectiles in shotguns, but is also used for a variety of other purposes....
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.

The operation of the hydrometer is based on the Archimedes

Archimedes

Archimedes of Syracuse was a Greek mathematics, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity....
principle that a solid suspended in a liquid will be buoyed up by a force equal to the weight of the liquid displaced. Thus, the lower the density of the substance, the lower the hydrometer will sink. (See also Relative density and hydrometers

Relative density

Relative density, sometimes called specific density, is the ratio of the density of a substance to the density of a given reference material....
.) Some historians credit Hypatia of Alexandria

Hypatia of Alexandria

Hypatia of Alexandria was a Greeks scholar from Alexandria in Ancient Egypt, considered the first notable woman in mathematics, who also taught philosophy and astronomy....
with the invention of the hydrometer although there is little evidence to support this.

In low density liquids such as kerosene

Kerosene

Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin, is a combustible hydrocarbon liquid....
, gasoline

Gasoline

File:GasCan.jpgGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines.It consists mostly of aliphatic hydrocarbons, enhanced with iso-octane or the aromatic hydrocarbons toluene and benzene to increase its octane rating....
, and alcohol

Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
, the hydrometer will sink deeper, and in high density liquids such as brine

Brine

File:Kissingen-Solepumpe-1848.JPGFile:Kissingen-Solepumpe-1848-2.JPGBrine is water Saturation or nearly saturated with a Salt .It is used to preserve vegetables, fish, and meat, in a process known as brining ....
, milk

Milk

Milk is an opaque white liquid produced by the mammary glands of female mammals . It provides the primary source of nutrition for newborn mammals before they are able to digestion other types of food....
, and acid

Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
s it will not sink so far. In fact, it is usual to have two separate instruments, one for heavy liquids, on which the mark 1.000 for water is near the top of the stem, and one for light liquids, on which the mark 1.000 is near the bottom. In many industries a set of hydrometers is used — covering specific gravity ranges of 1.0–0.95, 0.95–0.9 etc — to provide more precise measurements.

Commercial uses

Because the commercial value of many liquids, including sugar solutions, sulfuric acid

Sulfuric acid

Sulfuric acid, hydrogen2sulfuroxygen4, is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry....
, and alcohol beverages such as beer

Beer

Beer is the world's oldest and most widely consumed alcoholic beverage and the third most popular drink overall after water and tea. It is produced by the brewing and Fermentation of starches, mainly derived from cereal?the most common of which is malted barley, although wheat, maize , and rice are widely used....
and wine

Wine

Wine is an alcoholic beverage often made of fermentation grape juice. The natural chemical balance of grapes is such that they can ferment without the addition of sugars, acids, enzymes or other nutrients....
, depends directly on the specific gravity, hydrometers are used extensively.

A lactometer

Lactometer

Lactometer or Galactometer, a simple instrument used in testing the richness of milk, is graduated into a hundred parts. Milk is poured in and allowed to stand until the cream has formed, then the depth of the cream deposit in degrees determines the quality of the milk. Another instrument, invented by Doeffel, is two inches...
is a hydrometer used to test milk. The specific gravity of milk does not give a conclusive indication of its composition since milk contains a variety of substances that are either heavier or lighter than water. Additional tests for fat content are necessary to determine overall composition.

An alcoholometer

Alcoholometer

Alcoholometer is a special type of hydrometer which is used for determining the alcoholic strength of liquids. Alcoholometers have scales marked with volume percents of "potential alcohol", based on a pre-calculated specific gravity....
is a hydrometer which is used for determining the alcoholic strength of liquids. It is also known as a proof & traille hydrometer.

A saccharometer

Saccharometer

A Saccharometer is a type of hydrometer that measures the amount of sugar in a solution. It is used primarily by winemaker and brewing, and it can also be used in making sorbet....
is a hydrometer used for determining the amount of sugar in a solution. It is primarily used by brewers and winemakers.

A thermohydrometer is a hydrometer that has a thermometer

Thermometer

The thermometer is a device that measures temperature or temperature gradient using a variety of different principles; it comes from the Greek language roots thermo, heat, and meter, to measure....
enclosed in the float section.

For measuring the density of petroleum products, like fuel oils, the specimen is usually heated in a temperature jacket with a thermometer placed behind it since density is dependent on temperature. Light oils are placed in cooling jackets, typically at 15^oC. Very light oils with many volatile components are measured in a variable volume container using a floating piston

Piston

A piston is a component of reciprocating engines, pumps and gas compressors. It is located in a Cylinder and is made gas-tight by piston rings....
sampling device to minimize light end losses.

As a battery test it measures the temperature compensated specific gravity and electrolyte temperature.

Soil analysis

A hydrometer analysis is the process by which fine-grained soils, silt

Silt

Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
s and clay

Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
s, are graded. Hydrometer analysis is performed if the grain sizes are too small for sieve analysis

Sieve analysis

A sieve analysis is a practice or procedure used to assess the particle size distribution of a aggregate.The size distribution is often of critical importance to the way the material performs in use....
. The basis for this test is Stoke's Law for falling spheres in a viscous fluid in which the terminal velocity of fall depends on the grain diameter and the densities of the grain in suspension and of the fluid. The grain diameter thus can be calculated from a knowledge of the distance and time of fall. The hydrometer also determines the specific gravity

Specific gravity

Density

The density of a material is defined as its mass per unit volume. The symbol of density is ....
) of the suspension, and this enables the percentage of particles of a certain equivalent particle diameter to be calculated.