Refractometer
Encyclopedia
A refractometer is a laboratory or field device for the measurement of an index of refraction
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

(refractometry
Refractometry
Refractometry is the method of measuring substances' refractive index in order to, for example, assess their composition or purity. A refractometer is the instrument used to measure refractive index...

). The index of refraction is calculated from Snell's law
Snell's law
In optics and physics, Snell's law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass...

and can be calculated from the composition of the material using the Gladstone-Dale relation
The Gladstone–Dale relation is used for optical analysis , or to calculate the density of a liquid for use in fluid dynamics .The relation has also been used to calculate refractive index of glass and minerals in optical mineralogy The Gladstone–Dale relation (J. H. Gladstone and T. P. Dale, 1864)...

.

## Types of refractometers

There are four main types of refractometers: traditional handheld refractometer
A traditional handheld refractometer is an analog instrument for measuring a liquid's refractive index. It works on the critical angle principle by which lenses and prisms project a shadow line onto a small glass reticle inside the instrument, which is then viewed by the user through a magnifying...

s, digital handheld refractometer
Digital handheld refractometer
A digital handheld refractometer is an instrument for measuring the refractive index of materials.-Principle of operation:Most operate on the same general critical angle principle as a traditional handheld refractometer. The difference is that light from an LED light source is focused on the...

s, laboratory or Abbe refractometer
Abbe refractometer
An Abbe refractometer is a bench-top device for the high-precision measurement of an index of refraction.- Details :Ernst Abbe , working for the Zeiss Company in Jena, Germany in the late 19th century, was the first to develop a laboratory refractometer...

s, and inline process refractometer
Inline process refractometer
Inline process refractometers are a type of refractometer designed for the continuous measurement of a fluid flowing through a pipe or inside a tank. These refractometers typically consist of a sensor, placed inline with the fluid flow, coupled to a control box...

s. There is also the Rayleigh Refractometer used (typically) for measuring the refractive indices of gases.

In veterinary medicine
Veterinary medicine
Veterinary Medicine is the branch of science that deals with the prevention, diagnosis and treatment of disease, disorder and injury in non-human animals...

, a refractometer is used to measure the total plasma protein in a blood sample and urine specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

.

In drug diagnostics, a refractometer is used to measure the specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

in human urine.

In gemmology, a refractometer is used to help identify gem materials by measuring their refractive index.

In marine aquarium
Marine aquarium
A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only , fish only with live rock , and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally...

keeping, a refractometer is used to measure the salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

and specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

of the water.

• Ernst Abbe
• Refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

• Gemology
Gemology
Gemology or gemmology is the science dealing with natural and artificial gems and gemstones. It is considered a geoscience and a branch of mineralogy...

• Must weight
Must weight
Must weight is a measure of the amount of sugar in grape juice , and hence indicates the amount of alcohol that could be produced if it is all fermented to alcohol, rather than left as residual sugar...

• Winemaking
Winemaking
Winemaking, or vinification, is the production of wine, starting with selection of the grapes or other produce and ending with bottling the finished wine. Although most wine is made from grapes, it may also be made from other fruit or non-toxic plant material...

• Harvest (wine)
Harvest (wine)
The harvesting of wine grapes is one of the most crucial steps in the process of winemaking. The time of harvest is determined primarily by the ripeness of the grape as measured by sugar, acid and tannin levels with winemakers basing their decision to pick based on the style of wine they wish to...

• Gravity (beer)
Gravity (beer)
Gravity, in the context of fermenting alcoholic beverages, refers to the specific gravity, or relative density compared to water, of the wort or must at various stages in the fermentation. The concept is used in brewing and wine making industry...

• High-fructose corn syrup
• Cutting fluid
Cutting fluid
Cutting fluid is a type of coolant and lubricant designed specifically for metalworking and machining processes. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols , and air or other gases. They may be made from petroleum distillates, animal...

• German inventors and discoverers
German inventors and discoverers
This is a list of German inventors and discoverers. The following list comprises people from Germany or German-speaking Europe, also of people of predominantly German heritage, in alphabetical order of the surname. The main section includes existing articles, indicated by blue links, and possibly...

• High refractive index polymers
High refractive index polymers
A high-refractive-index polymer is a polymer that has a refractive index greater than 1.50.Such materials are required for anti-reflective coating and photonic devices such as light emitting diodes and image sensors...