Refractive index is a simple and accurate method for identifying the purity of organic compounds. For many binary systems, there is a fixed relationship between refractive index and composition, and therefore it is also commonly used as a parameter for detecting components. The refractive index is an important optical property of transparent materials. When the refractive index of the measured material is between 1.3000 and 1.7000, the total reflection method has the advantages of convenient and rapid operation, low requirements for environmental conditions, and no need for monochromatic light source. Abbe refractometer is an instrument that uses the total reflection method to measure the refractive index of transparent or semi transparent liquids. Measuring the refractive index of a liquid using an Abbe refractometer to determine its composition is one of the commonly used analytical and detection methods in production and scientific research such as petrochemical and light industrial food.
At different temperatures, the refractive index of the same medium is different, so it is necessary to compare the refractive index of different media under the same temperature conditions. The refractive index of transparent materials is closely related to their temperature and composition. Usually, the refractive index of solvents is measured within the temperature range of (5-30) degree . The Abbe refractometer should be kept at the corresponding temperature for two hours before it can be used for measurement.
The influence of media on the propagation speed of light at different wavelengths varies, so measuring the refractive index of the same medium using incident light at different wavelengths varies. The Abbe refractometer selects the D-line 589.3mm of sodium yellow light as the incident light through the Amish dispersion prism
The refractive index range of substances that can be measured by a refractometer is 1.30~1.70iii.
Requirements for relative humidity: The standard working curve of a refractometer with a relative humidity of less than 85 percent . Firstly, at atmospheric pressure and a temperature of 30 degree , the refractive index of binary mixed solutions with different proportions and concentrations is measured using an Abbe refractometer. The relationship between the molar composition of the solution and the refractive index is determined, and the standard curve of the molar composition of the solution and the refractive index at that temperature is obtained.
