Gas collection by drainage method is a common method of gas collection in the laboratory. Which gases can be collected by drainage method?

Generally speaking, the most common gases insoluble or slightly soluble in water that do not react with water are O2, H2,N2, CO, NO, CH4, C2H2 and C2H4, while those easily soluble in water, such as CL2, cannot be used. The specific methods of gas collection by drainage method are as follows:

Fill the cylinder with water and place it in the sink with the mouth below the liquid level. Then place the gas outlet under the bottle mouth. Until all the water in the bottle is drained, the bottle is filled with gas. But there are drawbacks: the collected gas contains a large number of water droplets, which generally require a desiccant dryer.

The maximum condition of gas collection by drainage method is that the gas is insoluble in water. Taking oxygen collection as an example, we fill the cylinder with water, cover it with glass sheet, put it upside down in the sink, and extend the air guide pipe under the mouth of the cylinder. When bubbles enter the cylinder, the water is discharged. This is the drainage gas collection method. When collecting gas, do not collect it when there are bubbles coming out of the catheter. Let the air in the test tube and the catheter drain clean. Do not collect it until the air bubbles in the catheter are continuously and evenly released.