Water analysis methods can generally be divided into two major categories, namely physical analysis and chemical analysis. Classical moisture analysis methods have been gradually replaced by various moisture analysis methods. Currently, there are mainly five types of moisture analyzers on the market. 1. Karl Fischer moisture analyzers:
The Karl Fischer method, which is called the Fischer method, was a method for measuring the volume of water that was proposed by Karl Fischer in 1935. The Fischer method is the most specific and accurate method for determining water in various types of chemical methods. Although it is a classical method, it has been improved in recent years, improving accuracy and expanding the measurement range. It has been listed as a standard method for determination of moisture in many substances.
The Fischer-Tropsch method is an iodometric method. The basic principle is that when oxidizing sulfur dioxide with iodine, the need for quantitative water 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 quantitatively, basic substances must be added. Experiments have shown that pyridine is the most suitable reagent, while pyridine also has the ability to combine with iodine and sulfur dioxide to reduce the vapor pressure of both. Therefore, the reagent must be added to methanol or another solvent containing a reactive OH group to convert the pyridine anhydride pyridine to a stable methyl bisulfate.
2. Infrared moisture meter:
Infrared moisture analyzer infrared heating mechanism: When far infrared radiation to an object, it can absorb, reflect and transmit. However, not all molecules can absorb far-infrared radiation, and only those polar molecules that show electricity can work. Water, organic substances, and high molecular substances have a strong ability to absorb far-infrared rays. When these substances absorb the far-infrared radiation energy and make its molecules, the frequency of natural vibrations and rotations of atoms coincide with the frequency of far-infrared radiation, molecules or atoms are likely to resonate or rotate, resulting in greatly increased movement and conversion into The heat energy raises the temperature inside, so that the substance is quickly softened or dried.
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 gas. However, this method interferes more. Some cold-changeable gases, especially at higher concentrations, interfere with condensation than water vapor.
4. Microwave moisture meter:
The microwave moisture analyzer uses a microwave field to dry the sample to accelerate the drying process. It has the characteristics of short measurement time, convenient operation, high accuracy and wide application range. It is suitable for grain, paper, wood, textile and chemical products, etc. The determination of moisture in powdered and viscous solid samples can also be applied to the determination of moisture in petroleum, kerosene and other liquid samples.
5. Coulomb moisture meter:
Coulomb moisture meters are often used to determine the moisture content of gases. This method is easy to operate, quick to respond, and especially suitable for the determination of trace moisture in gases. If you use ordinary chemical methods, it is very difficult. However, electrolytic methods are not suitable for the determination of alkaline substances or conjugated diolefins.
HEPA Air Purifier
Take a deep breath, close your eyes, the world has the freshest oxygen ... Yu Quan's "Deep Breath" is well known to us, but as the environmental problems become more and more serious, the haze sky also increases, PM2.5 PM10 and so on Vocabulary has also been mentioned more and more, and air purifiers have quickly become popular on the market with this "air quality" trend. Along with this, the air-clean brand has sprung up, and various technologies are dazzling. Which ones are indeed effective and which are just tasteless propaganda? How does the Air Purifier bother us to get rid of pollution? And look at the editors for you.
Analysis of air purifier
The critical value of PM2.5 content is 75 μg / m3
The pollutants in the air mainly include soot, total suspended particulates, inhalable particulates (PM2.5) and fine particulates (PM10). The smaller the diameter of the particulates, the deeper the part that can enter the respiratory tract. 10 micron diameter particles It is deposited in the upper respiratory tract, and particles below 2 microns can penetrate 100% into the bronchiole and alveoli.
1k-5k air purifier prices vary greatly
The air purifier products on the market not only have various functions, but also have prices ranging from thousand yuan to tens of thousands. The pricing of imported products is generally higher than that of domestic brands. Except for the core technology of many brands, the promotion of purification effects is similar, and consumers need to choose according to demand.
The air quality standard of 74 key cities is only 4.1%
According to the data of the press conference held by the State Council Information Office on June 4, according to the new "Ambient Air Quality Standards", the six pollutants SO2, NO2, PM10, PM2.5, CO and O3 were evaluated, 74 new standards In the first phase of monitoring and implementation, the proportion of cities that met the ambient air quality standards was only 4.1%, and the other 256 cities implemented the old air quality standards, and the proportion of cities that met the standards was 69.5%.
Air purifier sales increased by 90.5% compared with last year
According to a report recently released by the China Electronics and Information Industry Development Institute, due to the haze weather, air purifiers have become the most concerned home appliance products, with sales of nearly 2.4 million units nationwide last year, a year-on-year increase of 90.5%; retail The amount reached 5.6 billion yuan, a year-on-year increase of 105.9%.
HEPA air purifier , the HEPA filter needs to be replaced in March
The filter of the air purifier is the same as the filter of the water purifier, and it is not effective for a long time. After long-term use, the accumulation of dust on the surface of the filter will also cause the filter to gradually fail. Therefore, when the haze is more serious, the non-washable HEPA filter needs to be replaced every three months.
Merchants claim that the purification rate is more than 99% for the concept of stealing
99% or even 99.99% seems to have become a slogan for many air purifiers on the market. Many brands of products promote their high removal rate of PM2.5 and formaldehyde. In fact, this kind of publicity is more of a kind. The slogan of stealing the concept, the removal rate of 99% is the effect of the material itself on PM2.5 and formaldehyde, not the effect of actually running in space.
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