1, test tube connected to a catheter, the catheter end into a beaker of water, hands pressed against the outer wall of the container, the catheter mouth bubbles. After letting go of the catheter there is a section of stable liquid column, the device does not leak.
2. Conical flask with syringe, pour water from the long-necked funnel until the lower end is submerged. Pull the piston outward to bubble at the lower end of the funnel, and plug it inward to have a stable column of water, the device is airtight.