There are three ways to check the airtightness of the device

1. Elevated temperature method.

Increasing the temperature of the gas in the gas generator system can temporarily increase its pressure, so that this integral part of the air escapes (bubbles can be observed at the liquid), and when the temperature returns to the initial temperature, this overall pressure decreases, causing a section of water column to be sucked in the air duct immersed in water.

If the device does not leak, the air inside is heated and expanded, and there are bubbles released at the catheter mouth, and the water column in the air duct rises after the hand is removed, and does not fall back for a long time, indicating that the device has good air tightness. If the device is leaking, the cause must be found out, adjusted, repaired or replaced before the experiment can be carried out.

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.

2. 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. 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.

When testing the air tightness, add water to the long neck funnel, so that the lower end is immersed in water, use hot water to slightly heat B or C device, if there are bubbles released at D, the water surface of the long neck funnel of A rises, stop heating, the liquid level of the long neck funnel in A returns to normal, and the catheter in D sucks - a section of water column, which proves that the air tightness is good.

How to check the airtightness of the device.

The method of checking the elasticity of the device is as follows:

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 air.

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 are two common methods of operation for the airtightness of the sock inspection 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.

A: There are three ways to do this.

One. After assembling the experimental instrument, put one end of the catheter into the water and heat the test tube, if after a while, there are continuous bubbles coming out of the catheter mouth, indicating that the device is airtight. If there is no above phenomenon, the air tightness is not good, and it is necessary to carefully use the above method to test it piece by piece.

Two. Put one end of the catheter in the water and cover the tube with your hand for a while, if there are continuous bubbles coming out of the catheter orifice, the air tightness is good.

Three. Put one end of the catheter into the water, if the other end of the catheter is inserted into the assembly instrument, when the front of the connected instrument is an empty reaction bottle with a jack, first use the separating funnel to add half a bottle of water to the bottle, insert the lower end of the separating funnel below the liquid level, and then add water dropwise. If the liquid level in the bottle rises, the air tightness is not good.

Summary: The first two methods use the characteristics of thermal expansion and cold contraction, and the third method uses the pressure, and the air tightness of the general inspection device is considered from these two factors.

The phenomenon on the first floor should be that when the tubes of the first bottle of D are reversed with each other, they ventilate to the tube on the left.

The air pressure will increase more and more.

Water gushes out of the tube on the other side. If the airtightness of the device is not good enough, this phenomenon will not be seen.

1. First pour water from the long-necked funnel until the lower end of the long-necked funnel is submerged.

2. Pull the piston outward to send a message and dust resistance The lower end of the long-necked funnel bubbles appear, and the device has good air tightness.

3. If you push the piston inward, it is found that the long-necked funnel forms a stable water column of slippery brother-chun, and at the same time close the spring clamp and pour water from the long-necked funnel, if a stable water column is formed, it proves that the device has good air tightness.

Methods to check the air tightness of the device: pumping and pumping method, liquid difference method, microthermal method. The principle of checking the air tightness of the device is as follows:

By changing the internal pressure, the difference between the internal and external pressure is formed, and the water column is generated. Taking the liquid difference method as an example, the specific steps of the Zen He people are as follows: assemble the equipment, clamp the spring clamp, and continuously inject water into the long-neck funnel, so that the water in the long-neck funnel is higher than the internal water surface of the device, forming a liquid level difference, if the liquid level difference is observed to be stable and does not decrease, it means that the air tightness is good.

Pumping and pumping

Principle: The air pressure inside the device is increased and decreased by using the pumping and pumping of the syringe. When pumping, the internal air pressure becomes smaller, the external air pressure is large, the outside air pressure is large, and the outside gas enters the test to form bubbles.

When pumping, the air pressure inside the device is high, and the water is pressed into the long-neck funnel to form a water column.

Steps: Assemble the device, the double-hole stopper of the Erlenmeyer flask, one for the long-neck funnel, and the other for connecting to the syringe. Fill the long-necked funnel with water until the bottom of the long-necked funnel is submerged below the surface of the water. Use a syringe to pump or pump air into the Erlenmeyer flask.

When pumping outward, there are bubbles at the lower end of the long-necked funnel, and when inflating, the liquid level in the long-necked funnel rises to form a water column, indicating that the airtightness is good.

Microthermal method

Principle: 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 decreases after cold contraction, and the external air pressure is large, and the water is pressed into the conduit to form a water column.

After assembling the equipment, put one end of the catheter into the water to form a closed system, cover the test tube with both hands, and observe the front in the water such as bubbles coming out of the catheter mouth, and after letting go, a section of water column enters the catheter, indicating that the air tightness is good.