How do you reunite a liquid column in a thermometer?

To reunite a liquid column in a thermometer, using a dry ice-alcohol slurry is effective because it allows for controlled cooling of the thermometer. When thermometers break, the liquid inside (often mercury or colored alcohol) can separate into small columns that do not return to a single column by themselves. By submerging the thermometer in a dry ice-alcohol slurry, the extreme cold causes the liquid to contract and helps the smaller segments of the liquid column to reunite effectively.

The dry ice creates a very low temperature environment that facilitates this process without causing thermal shock to the glass of the thermometer, which might happen with other methods. This gradual cooling is critical to avoid breaking the thermometer or damaging the internal workings of the liquid.

Other methods, such as using a hot water bath or a heat lamp, may not be appropriate as they can cause the liquid to expand and further separate the column instead of reuniting it. Room temperature exposure provides no significant change in temperature that would encourage the liquid to flow back together. The use of a dry ice-alcohol slurry remains the most reliable and effective method for this task.