Calibration and precautions of Abbe refractometer
Abbe refractometer can be directly used to measure the refractive index of the liquid, quantitatively analyze the composition of the solution, and identify the purity of the liquid. At the same time, the molar refractive index, molar mass, density, and dipole moment of polar molecules can also be related to the refractive index, so it is also an important tool for the study of the structure of matter. Refractive index measurement requires less sample volume, high measurement precision (refractive index can be accurate to 0.0001), and good reproducibility, so Abbe refractometer is a common optical instrument in teaching and scientific research.
The instrument should be calibrated regularly, or when there is doubt about the measurement data, the instrument can also be calibrated. For calibration, use distilled water or a glass standard block. If the measurement data is in error with the standard, use a watch screwdriver to correct the small hole in the handwheel through the dispersion. Carefully rotate the screw inside to move the cross line on the analysis board up and down. As long as the measurement data is compounded, when the sample is a standard block, the measurement data must be combined with the data calibrated on the standard block. For the refractometer with scale, the zero point of the scale on the dial of the refractometer may sometimes move It must be corrected. During calibration, use a glass with known refractive index, turn the pistol to make the scale reading equal to the refractive index, after eliminating the dispersion, then use the adjustment wrench to turn the adjustment screw in the front groove of the eyepiece to make the sensitive boundary line and the cross line first Just a little bit
Abbe refractometer is a kind of precise optical instrument, the following points should be paid attention to when using:
(1) Pay attention to protecting the prism when using it. When cleaning, only use lens-cleaning paper instead of filter paper. Don't touch the dropper mouth to the mirror surface when adding the sample. Abbe refractometers are not allowed for corrosive liquids such as acids and bases.
(2) For each measurement, the sample should not be added too much, generally only 2 to 3 drops are needed.
(3) Keep the instrument clean and protect the dial. At the end of each experiment, add a few drops of acetone to the mirror surface and dry with lens-cleaning paper. Finally, sandwich the mirror surface between the two prisms with two layers of mirror paper to avoid damage to the mirror surface.
(4) When reading, sometimes the clear light-dark boundary is not observed in the eyepiece, but it is deformed. This is because the prism is not filled with liquid; if an arc-shaped halo appears, it may be because the light is not directly irradiated Onto the condenser lens.
(5) If the refractive index of the sample to be tested is not within the range of 1.3 to 1.7, the Abbe refractometer cannot be measured, and the light-dark boundary is not visible.
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