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Refractometers - Atago refractometer

Acknowledgment: We are grateful to Dr. P. Cowled principal research scientist of the department of surgery of the University of Adelaide who donated the apparatus to the Society and Mr. G. Faresi from the department of chemistry who provided the back-ground. Additional information and photographs are from wikipedia and sales catalogues.

The first refractometer was developed by Ernst Abbe, in the late 1800s while working in the Carl Zeiss Laboratories in Jena .

His use of light refraction was based on the finding that while the speed of light and its direction is constant in a vacuum both speed and direction changes when passing through another medium. The change is due to the interaction of light and the atoms in the medium. The refractive index is derived from the ratio between such changes.

If the concentrations of a substance dissolved in a solution changes the light will be refracted differently depending on the concentration of the dissolved substance. Using these principles the refractometer is able to measure the concentration of protein, sugar or salt in a solution. The main use outside the laboratory is for quality control in the food and beverage industry, in medical biochemistry, or to measure salinity of water.


Refractometer used in the QEH Department of Surgery in 1970


Closer view of the active part of the refractometer showing the prism
(blue) and the cover plate.fluid is placed on the prism stage. The cover
plate is closed and the eye piece is used to read the concentration.


The cover plate is closed over the fluid. The legend describes the
manufacturer. The range of concentration of protein which can be
measured in this instance 0 -12 gm per 100.ml of fluid.


View through the eye piece. The boundary line crosses the scaleand
indicates the concentration of the solution.



Fifty years later, models are hand-held and digitised

A recent model of a refractor measures the salinity of water. The catalogue number indicates the effective range of the instrument


Three hand held refractometers used to measure sugar concentrations.
The catalogue numbers refer to the effective concentration range of the


A modern digital refractometer and printer