1. Traditional drying method, advantages: The instrument is cheap and versatile. Frame Type Jumbo Paper Roll Slitter jumbo roll with 1500mm maximum rewinding diameter Wenzhou Dongyin Machinery Manufacturing Co., Ltd. , https://www.doinmc.com
Disadvantages: poor accuracy; can only be measured to 10-3 level; volatile substances are also evaporated during the dry distillation, can not determine the true value of the moisture content of the substance, the test takes too long.
2. Spectrum, chromatography, Advantages: Can be measured to 10-6 levels. Disadvantages: expensive equipment; high environmental requirements; long preparation time (a few hours); not conducive to product process control.
3. Distillation azeotropy, Advantages: The price is relatively cheap, selectivity is good, suitable for measuring petroleum products. Disadvantages: The accuracy is also poor, and the measurement time is long. Products with larger water content are suitable.
4. Karl Fischer's volumetric method,
Advantages: There are many types of tests, and the relative coulomb method is more versatile. Less sensitive to side effects such as ketones and aldehydes. Disadvantages: Only 10-4 levels can be measured under optimum conditions; consumables (reagents) are large; measurement time is long.
5 advantages of Coleman's Coulomb method: The instrument is medium in price; it has less consumables; it can be measured to 10-6 levels; the time is short, and the general substance can be determined within 60 seconds under the premise of having a good injection volume. It is a process control and arbitration judgment. The best way. Disadvantages: Due to high accuracy and over-sensitivity, some substances with side reactions such as ketones and aldehydes are difficult to measure and require a certain amount of experience to control the reaction direction.
6 Other special methods: Capacitance / resistance method, suitable for rough testing of paper, wood, food and other substances; near-infrared method, suitable for on-line measurement of large water content substances; electrolysis (phosphoric acid) method, suitable for on-line gas measurement; pressure difference method, suitable Measurement of volatile substances; dew point method, suitable for measuring gases; in addition to cloud point method; phosphoric acid gravimetric method; crystallization method and other uncommon methods.