Moisture measurement can be the control analysis of industrial production, or the quality verification of industrial and agricultural products; it can be measured from tons of products, or it can be analyzed in the laboratory with only a few microliters of test solution; it can be the water content Constant moisture analysis of a few percent to tens of percent, but also trace moisture analysis with a moisture content of less than one part per million, etc. Picnic Blanket,Picnic Rug,Picnic Mat,Outdoor Blanket Ningbo Fineweather International Trade Co., Ltd. , https://www.fwsbag.com
Moisture analysis methods can generally be divided into two categories, namely physical analysis and chemical analysis. The classic moisture analysis method has been gradually replaced by various moisture analysis methods. At present, there are mainly the following 5 moisture analyzers on the market.
1. Karl Fischer Moisture Analyzer:
The Karl Fischer method is abbreviated as the Fischer method, which is the capacity split method for measuring moisture proposed by Karl Fischer in 1935. The Fischer method is the most specific and accurate method for measuring the water content of substances. Although it is a classic method, it has been improved in recent years to improve accuracy and expand the measurement range. It has been listed as the standard method for the determination of moisture in many substances.
The Fischer method is an iodometric method. Its basic principle is that when oxidizing sulfur dioxide with iodine, a certain amount of water is required to participate in the reaction:
12 Ten S02 Ten 2H2O = 2HI Ten H2SO4
The above reaction is reversible. In order to move the reaction in the positive direction and proceed quantitatively, an alkaline substance must be added. Experiments show that pyridine is the most suitable reagent, and at the same time, pyridine can also combine with iodine and sulfur dioxide to reduce the vapor pressure of both. Therefore, the reagent must be added into methanol or another solvent containing active OH groups to convert sulfuric anhydride pyridine into stable methyl bisulfate pyridine.
2. Infrared moisture meter:
Infrared heating mechanism: When far infrared rays radiate onto an object, absorption, reflection and transmission can occur. However, not all molecules can absorb far-infrared rays, and only work on polar molecules that show electricity. Water, organic substances and high molecular substances have strong properties of absorbing far infrared rays. When these substances absorb the energy of far-infrared radiation and make their molecules and atoms inherently vibrate and rotate at the same frequency as the far-infrared radiation, the resonance or rotation of molecules and atoms is extremely likely to occur, resulting in greatly increased motion, which is The heat energy increases the temperature inside, so that the material is quickly softened or dried.
The general heating method is the use of heat conduction and convection, which needs to propagate through the medium, which is slow and consumes a lot of energy. Far-infrared heating uses heat radiation without medium propagation. At the same time, because the radiant energy is proportional to the fourth power of the temperature of the heating element, it not only saves energy but also has high speed and high efficiency. In addition, far-infrared rays have a certain penetration ability. Since the heated and dried substances absorb far-infrared radiant energy in the interior and surface molecules of a certain depth, a self-heating effect is generated, which evaporates the solvent or water molecules and generates heat uniformly, thereby avoiding The deformation and qualitative change caused by different degrees of thermal expansion keep the appearance, physical and mechanical properties, fastness and color of the material intact.
The infrared moisture analyzer is mainly determined by the infrared radiant heater and the electronic balance to determine its accuracy and stability.
(Infrared radiation heater: Tungsten wire vacuum tube can radiate near infrared, silicon carbide is a long-wavelength far infrared radiation heater, quartz glass and ceramic infrared heater can radiate mid-infrared)
Infrared Moisture Analyzer "Moisture Loss Reduction Method", a recognized standard measurement method for moisture measurement standards, is very similar to an infrared moisture meter for heat drying and quality measurement. The "reduced drying method" of the accepted standard measurement method is also called (105 ° C? 5 hours method), (135 ° C 3 hours method), etc., by putting the sample in the dryer for long time heating and drying To accurately measure the mass change before and after drying to calculate the moisture content. For this reason, it is necessary for the measurement personnel to be very proficient in equipment and technology. Because the measurement requires a long time, it is difficult to quickly measure a large number of samples. Therefore, for the measurement of a variety of samples with high accuracy, except for the infrared moisture meter, it is not thought of. Although there are some other electrical and optical measurement methods, they are all special instruments that limit the measurement object. From the perspective of versatility, they are far less than infrared moisture meters.
Scope of application: It can measure food-related items such as grains, starch, flour, dried noodles, brewed products, seafood, processed fish products, processed edible meat products, spices, points, hearts, dairy products, dried foods, vegetable oils, etc , Ore sand, coke, glass raw materials, cement, chemical fertilizers, paper, pulp, cotton, various fibers and other industrial products.
3. Dew point moisture meter:
The dew point moisture analyzer is easy to operate, the instrument is not complicated, and the measured results are generally satisfactory. It is often used for the determination of trace moisture in permanent gases. However, this method has more interference, and some easily exchangeable gases will cause condensation before water vapor condenses, especially at higher concentrations.
4. Microwave moisture meter:
The microwave moisture analyzer uses the microwave field to dry the sample to speed up the drying process. It has the characteristics of short measurement time, easy operation, high accuracy and wide application range. It is suitable for granular, paper, wood, textile and chemical products, etc. The determination of moisture in powder and viscous solid samples can also be applied to the determination of moisture in petroleum, kerosene and other liquid samples.
5. Coulomb moisture meter:
The Coulomb Moisture Analyzer is commonly used to determine the moisture content of gases. This method is simple in operation and quick in response, and is particularly suitable for measuring trace moisture in gas. If it is determined by a general chemical method, it is very difficult. However, the electrolytic method is not suitable for the determination of alkaline substances or conjugated diolefins.