How to check the tightness and what is the method to check the tightness

How to check the airtightness of the device.

Ways to check the tightness:

1. Thermal expansion and cold contraction method.

Immerse the lower end of the catheter in water, hold the test tube tightly with your hand, if there are bubbles coming out of the catheter mouth, after releasing your hand, the water enters the catheter to form a water column, which proves that the device is airtight.

The thermal expansion and cold contraction method is often used to check the air tightness of the experimental device for the production of oxygen by hot potassium permanganate, and its main principle is: the gas inside the device is heated and expanded through micro-heat, and a part of the gas is overflowed, and after cooling, the pressure of the gas in the device is reduced after cold contraction, and the external air pressure is large, and the water is pressed into the conduit to form a water column.

2. Water injection method.

Add water to the long-necked funnel until the water immerses the lower end of the long-necked funnel, form a liquid seal, close the water-stop clip, and continue to add water to the long-necked funnel.

3. Pumping method.

1) Add water to the long neck funnel until the water immerses the lower end of the long neck funnel to form a liquid seal, slowly pull the syringe piston outward, if you see air bubbles coming out of the Erlenmeyer flask, it proves that the device has good air tightness.

2) Add water to the long neck funnel to submerge the lower end of the long neck funnel to form a liquid seal, slowly push the syringe piston inward, if you see a section of water column formed in the long neck funnel, it proves that the device has good air tightness.

4. Liquid level difference method.

Clamp the rubber conduit part with an air stop clip, add water to the long neck funnel, immerse the lower end in water, continue to add water to form a water column, produce a height difference, and the water column does not fall back for a period of time, indicating that the air tightness is good.

Here's how to check the airtightness of the device:

1. Microthermal method This is one of the most commonly used methods for the air tightness of middle school chemical testing devices, and it is also the most basic method for testing the air tightness of the device The principle of this test method is to use the gas to escape from the device after being heated and expanded, and see the bubbles coming out.

Here's how it works:

Insert the end of the trachea B into the water tank, hold the test tube A with your hand or heat it slightly with an alcohol lamp, so that the gas in the test tube A is heated and expanded, and there will be bubbles at the end of the trachea After releasing the hand or withdrawing the alcohol lamp, there is a section of water column rising at the end of the trachea, which proves that the device has good air tightness and does not leak.

2. The liquid difference method is to use the "supporting force" generated by the pressure difference between the inside and outside of the device to hold up a section of water column and no longer drop For different experimental devices, when using the liquid difference method to test the air tightness, the experimental operation methods adopted are different.

The following describes two common operation methods for testing the air tightness of the device by the liquid difference method:

1) Air tightness inspection of Qipu generator:

Close the piston of the air duct and add water to the spherical funnel so that the liquid level in the funnel is higher than the liquid level of the container, and when the liquid level does not change after standing for a while, it can prove that the air tightness of the Qipu generator is good.

2) Another method of air tightness testing:

Connect the instrument and inject an appropriate amount of water into tube B so that the liquid level of tube B is higher than that of tube A. After a few moments, if the liquid level remains the same, it is a sign that the device is airtight.

3. The liquid sealing method is shown in the figure below, and the method of air tightness inspection of the device is as follows:

Close the piston k, add water to it to immerse the lower end of the funnel nozzle, if there is a stable water column in the funnel neck, it proves that the device has good air tightness It should be noted that:

In order to check the airtightness of the whole device, in order to form a certain air pressure difference and produce an obvious phenomenon, you can use an alcohol lamp to slightly heat a container that can be heated in the device, and then observe whether there are bubbles coming out of the air duct mouth where the liquid is inserted, so as to judge whether the airtightness of the whole device is good.

1.Use gas thermal expansion and contraction to test: cover the bottle with both hands, put the guide mold tube into the water, if there are bubbles, the air is tight.

2.Use atmospheric pressure.

Inspection: Hyphenic number.

device, seal the air outlet of the eggplant, add water to the funnel, if the liquid level does not fall, it is airtight.

3.The use of liquid level pressure difference is slow: closed device, U-shaped pipe to add water to the nozzle at both ends of the liquid level is not the same, if the liquid level does not drop, then the air tight.

There are two main ways to check the air tightness of the device:

1. Temperature elevation method.

Raising the temperature of the gas in the gas generator system can temporarily increase the pressure, allowing the entire air to escape (bubbles can be observed at the liquid), and when the temperature returns to the initial temperature, the overall pressure decreases, causing the water to be drawn into the water-immersed airway tube and a water column is formed.

1. For some devices with a small amount of gas, you can use the hand holding method to immerse one end of the pipeline in water, and put both hands close to the outer wall of the container (test tube). If the device is not leaking, the air inside is heated and air bubbles at the pipe mouth are released. When the hand is removed, the water column in the air pipe rises and does not recede for a long time, indicating that the device is airtight.

If the device is leaking, the cause must be found out, adjusted, repaired or replaced before the experiment can be carried out.

2. The above method has its disadvantages, if the temperature of the environment is close to the temperature of the human body, the method of holding it by hand, the phenomenon is not obvious enough, and the microthermal method should be used. That is to say, when the temperature of the hand is about the same as the temperature of the environment, the hand grip can not change the overall temperature and pressure, use the alcohol lamp to heat slightly at the bottom of the container (the container that can be heated directly or indirectly with the alcohol lamp), or immerse the container in hot water, if there are bubbles in the water, after the heating is stopped, there is a section of water column in the conduit, and it does not fall back for a period of time, indicating that the device has good air tightness.

Second, the liquid level difference method.

Clamp the rubber conduit part with an air clip, add water in the long neck funnel, immerse the lower end in water, continue to add water to form a water column, resulting in a height difference, if the water column remains the same and does not fall back, keep it for a period of time, indicating that the air tightness is good. For specific questions. Be specific, such as:

Hydrogen is produced in the laboratory, and after removing impurities (HCI gas and moisture), it can be used for other purposes.

To test the air tightness, add water to the long-neck funnel, immerse the lower end in water, and heat the B or C unit with hot water. If there are bubbles at D, the water surface of the long-necked funnel of A rises, the heating stops, the liquid level of the long-necked funnel returns to normal, and the catheter in D sucks the water column of the section, which proves that the air tightness is good.