Posted 31 Dec 2010 20:20
Measuring transparent or translucent liquid or solid dispersion of the refractive index of ND and the average NF-NC equipment. Instrument connected with a thermostat, the temperature can be determined 0 ~ 70 refractive index within the ND, and can measure the concentration of sugar solution in the percentage of sugar content. Therefore, this device is the oil industry, oil industry, pharmaceutical industry, paint industry, food industry, daily chemical industry, sugar industry and geological survey and other related plants, essential teaching and research units of commonly used equipment. Theory according to the law of refraction, angle of incidence i and refraction angle r between the following relationship: when the light from the medium 1 into medium 2, is = n1, 2 (5-3) where n1, n2, v1, v2, respectively 1 , 2, and the refractive index of the two media in which the propagation speed of light, n1, 2 medium 2 to medium 1 is the relative refractive index. Constant for the material properties of the refractive index of a certain wavelength of light in a certain temperature and pressure, is a constant. From (5-3) shows that, when n2n1, then the angle of refraction r is less than constant angle of incidence i. Increased when the angle of incidence i, the angle of refraction corresponding to maximum rc, rc is called the critical angle. At this point in medium 2 from OY to the light to pass through between OA and OA compared to the dark zone between OX, as shown in Figure 5-3. When the incident angle too, the above equation can be written as: n2 = n1sinrc (5-4) that is fixed a medium, the critical size and the refractive index of refraction rc have a simple function. Abbe Refractometer principle is based on this principle of design. Figure 5-4 Schematic diagram of the instrument structure. Its main part is the two right-angle prism PI, PII, PI of the rough surface and prism PII AD between the optical flat mirror of about 0.1 to 0.15mm gap, used to hold the liquid under test and to the PI, PII paved between a Book layer. Injection of light from the reflector prism PI, due to the surface is rough ground glass diffusion occurs, the gap from various angles measured by the liquid; into the prism PII, the former know, from all directions into the prism PII refraction of light are produced, and its angle of refraction rc fall within the critical angle (since the refractive index of the prism is greater than the refractive index of liquid, so the angle of incidence of light from the whole and can be refracted through the prism). Rc with the critical angle prism of light piercing shot in the eyepiece after PII, this time If the crosshair eyepiece adjusted to the appropriate location, will see the eyepiece on the half-dark. From the geometrical optics can be shown that the gap in the liquid and the liquid refractive index n relationship between rc: n liquid = sinB B on a certain prism is a constant, n is the prism at a constant temperature setting. Therefore, the refractive index of liquid n liquid is a function of angle of rc. Rc calculated from the refractive index of liquid. Refractometer reading rc has been converted to the value of n solution can be directly read out the value of n solution. Specified conditions, the refractive index of the liquid due to the wavelength of monochromatic light used varies. If using ordinary white light as the light source, then as a result of dispersion presented in the light and dark colored band of light at the line, so that the junction of light and dark is not clear. In order to white as the light source can be used, so the instrument is also equipped with two of the three prism formed by the West to Miami as compensation prism prism (above a prism can be rotated Miami West), adjust their relative position in the appropriate orientation , you can make out from the following dispersion prism of light refracted back into white light, remove the ribbon, so that clear lines of light and shade. At this point, with a white light which is equivalent to the refractive index measured with sodium D line light (wavelength 5890 people) the measured refractive index nD. Constant refractive index of one of the characteristics of the material, its value and the temperature, pressure and light source wavelength and so on. When symbol is used in the sodium D line as the source of light when the refractive index of the material. Influence of temperature on the refractive index. Most of the temperature of each liquid organic material increases, the refractive index down to, and the solid relationship between refractive index and temperature is not law, not more than. Usually the change of atmospheric pressure values of the refractive index is not obvious, only in a very sophisticated work before considering the pressure. Use (1) prism 5 and 6 open, use lens cleaning paper to wipe clean the mirror after the mirror a few drops of liquid sample, and it covered the whole mirror off the prism. (2) adjust the mirror so that incident light 7 to the strongest, and then turn the prism to the eyepiece appears half-light, the line at the intersection of cross lines, then 2 from the magnifying glass to read on the scale of the refractive index of liquid . (3) appears with a colored light, adjust the achromatic compensator, so that with the disappearance of colored light, dark clear interface. (4) After the test finished, open the mirror prism and washed with ****, can also be sucked dry ear mirror ball, end of the experiment, in addition to the need to clean the mirror, but still need to clip the two layers of lens cleaning paper to tightening the two prisms closed bolts to avoid mirror damage. Scale zero Abbe Refractometer calibration before use, will have to be the ruler zero point correction, the standard can be known refractive index liquid (such as pure water = 1.3325), can also be used in each with a known refractive index refractometer The glass block correction. A-bromo naphthalene can be used to block the light side of the glass adheres to the refraction prism 5, do not close the prism 6, open the small window behind the prism so that the light this injection, were determined using the above method, if the measured value and the glass the refractive index of the block are different, rotating on the tube to adjust the calibration screw K.