Under certain conditions, matter often has a certain refractive index. When mixed with other substances, its refractive index will also change. It can be used to identify different kinds of oils and check the purity of all oils by refractive index. If some substances contain other substances, they will show different refractive indices due to their different components. Therefore, the concentration of certain solutions can be calculated by measuring refractive index.
1. Methods of use
1, the refractometer should be placed on a platform with sufficient light (not subject to direct sunlight) and equipped with thermometers. If necessary, thermostat can be connected to maintain a certain temperature.
2. Make the prism transparent to the light source and pull the barrel to the observer, so as to make an appropriate inclination.
3, aligning the reflector to make the most bright light in the field of vision. If in the evening or the indoor light is not enough, or detect the darker specimen, we can open the prism round window to increase the intensity of light.
4, pull the prism open, use a glass rod or a straw to pick up a little (1-2 drops) on the mirror, then close the two prisms up and down, and fasten it.
5, the scale rotary knob, so the reading in the vicinity of sample refractive index, and then rotating compensator knob, so that the vision in the rainbow disappeared, a clear line of demarcation of a light, then turn the scale knob, the field terminator is located at the cross point, so repeated 3 times, average 3 readings.
6, open the reading tube small reflector, properly light, record the reading and temperature on the scale, that is, the refractive index of the product at this temperature, the left side contains the percentage of sucrose, and the right side is the refractive index reading.
7, measured as samples for aqueous solution, should immediately use absorbent cotton to absorb the test liquid, and then drops of distilled water to the prism, and then cotton dry, repeated washing 3 times, finally wiping paper or cotton gently wipe clean, such as inspection for oil substances, should immediately be by prism method two wipe clean with toluene or ethyl ether absorbent cotton.
Two, correction method
When the refractometer is used for a period of time, it needs to be corrected
1, pure distillation water correction method. Refractive index of pure distilled water at 20 DEG C when the correction rate was 1.3330, with the same procedure for determination of seized goods, such as 20 degrees in the refractive index at 1.3329-1.3331. said this refractometer is correct, the temperature at 20 degrees Celsius temperature should be 20 degrees in the conversion, such as the refractive index in the range of 1.3329-1.3331 to be. Adjust the dial, the reading at 1.3330, then the key is inserted into the tube side holes, gently turn the adjusting screw until the field terminator is located at the cross point.
2, standard glass block correction method. The refractometer usually has the standard glass block used for the correction, and the correction method is as follows:
(1) the refractometer is placed on a platform with bright light without direct sunlight, and the light can be directly injected into the prism without a reflector.
(2) will be opened on the prism, the prism flat, the standard glass blocks light surface adhesion on prism with bromonaphthalene liquid, and make a smooth light standard glass block toward the light, and with a small piece of paper on top of standard glass block.
(3) in addition to marking its refractive index, the standard glass block also indicates the temperature, which is corrected by the thermostat. Otherwise, the temperature at correction should be recorded and converted.
(4) the rotary compensator knob makes the iris disappearing and then rotates the dial knob to make the readings equal to the rate of refraction written on the standard glass block.
(5) the observation in the field such as the terminator is located at the cross point, said the refractometer is correct, if not, the application key is inserted into the tube side holes, gently turn the adjusting screw until the field terminator is located at the cross point.