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If the column of mercury (or other indicating fluid) in a thermometer separates, the void will render the indicated temperature inaccurate. Here are some ways to remove the void in the column. Please read all the steps before attempting this.

  1. Do not use it anymore if it is cracked or damaged in any way. It has served its life and needs to be disposed of properly (see Warnings below). [1]
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Method 2
Method 2 of 4:

Warming

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This method may take several attempts.

  1. The mercury will rise to the top of the thermometer and join together.
  2. Do not overheat, as the thermometer could burst. [3]
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Method 3
Method 3 of 4:

Shaking

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This method is fairly reliable as it was often used in hospitals, etc. before the electronic thermometers and disposable temperature strips became commonplace. There is, however, a risk of losing grip of the thermometer while shaking that could result in breakage and spillage of mercury.

  1. Firmly grasp the thermometer near the top, so that the bulb containing the mercury (or other indicating fluid) is pointed downward. [4]
  2. When the thermometer reaches the lowest point of the stroke several times. [5]
  3. If the indicated temperature has been reduced from the last time checked, continue shaking the thermometer downward. It will likely require repeating many times before the void in the column has disappeared.
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Method 4
Method 4 of 4:

Dropping

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This method seems to have the best results, but also risks breakage of the thermometer if dropped from too high or on to a hard surface.

  1. Not more than a one or two foot drop is recommended. [6]
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Community Q&A

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  • Question
    Is mercury dangerous if ingested?
    Community Answer
    Yes, do not ingest mercury. It could lead to mercury poisoning, which makes you violently ill.
  • Question
    How long should I keep the thermometer in the freezer?
    Community Answer
    Keep it in the freezer until the mercury or indicating fluid reaches the bulb.
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      Warnings

      • Do not simply "throw away" a device containing mercury. Mercury is a heavy metal, and is highly toxic. In many places, it is illegal to improperly dispose of mercury. Contact your locality's hazard waste office to learn how to dispose of mercury containing thermometers and other devices. Never mix devices that contain mercury in with common household trash.
      • Consider discontinuing the use of thermometers containing mercury if it is used for cooking or is a clinical thermometer. Since mercury is highly toxic, using them in food or in the body is discouraged. New electronic thermometers and those that use a red dye and alcohol mixture are much easier to read and safer to use.
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      About This Article

      Article Summary X

      If your mercury thermometer is cracked, you can't repair it, and you should instead discard it safely, since mercury is toxic. Never just “throw away” your thermometer but call your local hazard waste office to find out how to safely discard it. However, if your thermometer has seemingly stopped working, you can repair it by placing the thermometer in a refrigerator or freezer. If it’s cold enough, it may restore the mercury column on your thermometer. For other ways to repair your thermometer, including how to repair it by shaking or even dropping it, keep reading!

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