Why do refractometers have errors when measuring
Refractometers are common instruments in laboratories, and they can be used to understand the optical properties, purity, concentration, and dispersion of substances. It is widely used in scientific research and petroleum, oil, pharmaceutical, paint, food, sugar, daily chemical and other industries. A refractometer can measure the refractive index formed when light is irradiated into a substance, so as to determine certain conditions of the substance. As long as it is a measurement instrument, it will inevitably be affected by various factors, resulting in certain errors in the measurement results. , so we cannot ignore these errors when using measuring instruments, but should take them into account to ensure the accuracy of the measurement. The factors that affect the Abbe refractometer include light wavelength, temperature, air pressure, etc. The errors caused by different influencing factors are different. When performing measurements, you should consider it in advance and have a way to deal with it! Xiaobian will discuss it in this article There are two major factors that affect the measurement error of Abbe refractometer - light wavelength and temperature.
The first is the influence of light wavelength on the refractive index measured by the refractometer. Light waves refer to electromagnetic waves with wavelengths ranging from 0.1mm to about 0.1wm. The wavelength of this electromagnetic wave is long or short, and the wavelength of different lengths has an impact on the refractive index. If the wavelength is longer, the refractive index is smaller, and if the wavelength is shorter, the refractive index is larger. The light source we use when we measure the refractive index is generally white light. White light will produce dispersion phenomenon, that is, when white light is refracted by the prism and the sample liquid, the degree of refraction of different wavelengths is different, and after refraction, it is decomposed into a variety of colored lights. And these multiple colors will hinder the line of sight from distinguishing the dividing line between light and dark, resulting in measurement errors. In order to eliminate this obstacle, the Abbe refractometer has a special design, that is, a dispersion compensator is installed at the lower end of the observation tube, which can solve this problem well.
The second is the effect of temperature on the refractive index of the refractometer. The measured refractive index is also different when the temperature of the solution is different. The specific relationship between temperature and refractive index is as follows. Generally, when the temperature rises, the refractive index decreases, and when the temperature decreases, the refractive index increases. Therefore, it is necessary to ensure that the temperature during measurement is 20°C, and the temperature marking of the refractometer is also 20°C. If it is really impossible to ensure that the temperature is at 20°C, it can be handled as follows: when it exceeds 20°C, add the correction number, otherwise, subtract the correction number. In this case, it is also possible to subtract the error value, so as to ensure the accuracy of the measurement! To reduce the measurement error of the refractometer, in addition to avoiding the interference of the above two factors, it is also necessary to operate the instrument correctly and perform zero adjustment before use. .
