52
Supplemental Information
•
Refractive Index and Brix
What is a refractometer?
When a straw is placed into a glass filled with water, the straw
appears to bend. When a straw is placed into a glass filled with
sugar water, the straw appears to bend much more sharply than in
the case of water alone. This phenomenon is known as the
refraction of light. The refractometer is an instrument that
measures the Refractive Index by utilizing this principle (the
Refractive Index increases in proportion to the concentration of
the solution), and was developed by Dr. Ernest Abbe at the end of
the 19th century.
What is refractive index? (See the above figure)
If the Refractive Index of air under atmospheric pressure is 1, then when light enters medium x, the ratio of
the sine of the incident angle α measured against the phase boundary to the sine of the refracting angle β
is called the Refractive Index of the medium x. The Refractive Index varies with the wavelength of light and
temperature and is represented as follows:
For example, the Refractive Index of water at 20℃ for
the D line is = 1.33299 (generally expressed in the
form of nD=1.33299).
Note :
The Refractive Index is based upon the supposition that the Refractive Index in a vacuum is 1 and is called
the absolute Refractive Index. Generally, however, this index is seldom used.
Brix scale
This instrument is equipped with the Brix scale on a refractive index of water (nD=1.33299) used as the
reference (0%).
Brix means the scale of the weight (%) of sucrose (grams of sucrose contained in 100 grams of sucrose
solution). Thus, if a sucrose solution is measured, it matches this concentration. However, almost all foods
contain not only sugar, but also a variety of dissolved components such as salt and protein. The total
concentration of these water-soluble materials is called the soluble solid content. When this sample is
measured, Brix is almost consistent with the soluble solid content (%) and is used as a practical scale.
※ The Brix scale is expressed in % mass (Sucrose) as the International System of Units (SI unit).
Temperature compensation
The Refractive Index of the same material will vary due to temperature. If the refractometer is used to
measure a solution, a change occurs in the measurement value depending on a difference in temperature.
The Brix or concentration value displayed by this product is automatically compensated by the built-in
computer based on the measured temperature and the same value is always displayed as if measurements
were made at 20℃ (in case of a sample temperature of 5 to 75℃).
n: Represents the Refractive Index
t: Temperature(℃)
D: D- line of sodium
To Next Page
Loading...
Need help?
General
