Empty the cane of mercury by tapping the bottom to the bottom of a jar. Alternatively, and more efficiently, insert an appropriately sized catheter, connected to a syringe, into the cane to suck out the mercury.
Clean the tube. Use another catheter to insert a solution of 50 percent nitric acid and deionized water into the tube. Then dry the tube by using a third catheter to inject ethanol.
Clean the mercury by injecting it through a clean cloth into a jar.
Reinject mercury into the cane, while holding the cane at 30 degrees to the horizontal. Connect a catheter to a syringe and use the syringe to take up the mercury. Connect the syringe to the cane and squirt out the mercury, being sure not to make air bubbles. If you see air bubbles, withdraw the mercury and reinject it.
Move the cane to a vertical position. If you see bubbles moving through the cane, remove your mercury and start over with a clean cane.
Size a small piece of cork to plug the end of the mercury tube. Insert the cork into the end of the tube.