1Freezing point osmometerAccording to the Raoult freezing point principle, based on the proportional relationship between the decrease in solution freezing point and the molar concentration of the solution, a highly sensitive temperature sensing element - thermistor - is used to measure the freezing point of different solutions.

2、 Dew point osmometer: using the principle of boiling point rise and water vapor pressure technology, the solution is heated to evaporate to measure the sample osmotic pressure. It is a measurement method that uses a thermocouple to condense the vapor generated by the evaporation of the solution sample.

The advantages of dew point method compared to freezing point method are:

1. No need to change the physical form of the substance

2. Can handle semi-solid samples commonly used in clinical and industrial chemistry laboratories using the freezing point method.

3. For samples containing suspended particles or high viscosity, accurate results can be easily obtained.

4. It can directly measure the osmotic pressure of plant and animal tissue slices. Such as plant leaves, animal brain and kidney slices.

Disadvantage: Dew point osmometers cannot be used to detect samples of volatile solutions such as ethanol and ether, especially those that are easily decomposed by heatFreezing point osmometerOkay.

3、 Colloidal osmometer: It is measured by a measuring cell, which is separated by a semi permeable membrane. The lower half is isolated from the outside and filled with Ringer's solution containing electrolytes, while the upper half is connected to the outside and filled with a solution containing colloids. The membrane only allows water and electrolytes to pass through, and the osmotic pressures of the two solutions are different. The solution can permeate from the lower half of the measuring cell to the upper half until the pressure in the lower half of the cell reaches equilibrium with the colloid molar concentration. Directly measure the pressure caused by changes in liquid static pressure.

4、 Membrane osmometer: The permeation tank is divided into two parts by a semi permeable membrane. In the sealed lower half, filled with pure solvent, a pressure gauge system is installed. In the upper measuring cell of the semi permeable membrane, a curved channel system is designed with a large surface area. The funnel and drainage system can be flushed and injected into the measuring tank with solvent. Due to the different osmotic pressures of the solvent and solution, a vacuum degree is formed in the lower half of the pool to represent the concentration of osmotically active dissolved particles.