ATAGO 3534, Инструкция по эксплуатации

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8
2. Refractive Index and Dimethylformamide (DMF)
concentration
The instrument is a refractometer that detects the Refractive Index of a sample and outputs the
DMF concentration(%) value on the display.
(1) What is 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. Ernst Abbe at the end of the 19th century.
(2) What is the Refractive Index?
If the Refractive Index of air under atmospheric pressure is 1,
then when light enters mediumχ, the ratio of the sine of the
incident angleαmeasured against the phase boundary to the
sine of the refracting angleβis called the Refractive Index of
the medium χ.
The Refractive Index varies with the wavelength of light and
temperature and is represented as follows:
For example, Refractive Index of water at 20℃ under the D-line is:
= 1.33299(Generally expressed as nD = 1.33299.)
m 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.
(3) DMF concentration(%) scale
The instrument is programmed with the DMF(%) scale, based on the Refractive Index of water
(nD = 1.33299) as the reference (0%).
(4) Temperature correction
The Refractive Index of a substance varies with temperature. Thus, when using a
refractometer to measure the Refractive Index of a liquid, the measurement value will vary with
the sample temperature.
The instrument always detects the prism temperature. The value of the measurement is
automatically corrected for temperature by a built-in processor, so that the displayed value is
equal to the value measured at 20 ℃ (provided that the sample temperature is within the
range of 5 to 40 ℃).
n ：Represents the Refractive Index
t ：Temperature (℃)
D ：D-line of natrium (589nm)
Air
Medium χ
n=1
α
β
nχ=
sin α
sin β