FAQs

Do you need instructions to reunite separated thermometer liquid? Maybe you’re wondering about the benefits of Teflon® or what the difference is between partial and total immersion. All that and more can be found here. Our Quick Reference page is designed to provide information and help answer your technical questions.

Fact # 1 - Thermometers separate
Fact # 2 - Incase of separation, thermometer liquid can be reunited
Fact # 3 - With misuse, thermometer's can be inaccurate
Fact # 4 - Calibrated and certified thermometers
Fact # 5 - Thermometers may need to be recalibrated
Fact # 6 - Thermometers come with a variety of liquid options
Fact # 7 - Contamination of any sort can be detrimental
Fact # 8 - Conversions are simple
Fact # 9 - Further questions

Solution:
Proper shipping and storage of thermometers can help prevent separation. When shipping thermometers, pack them on an angle using packing peanuts & bubble wrap. This will also prevent thermometer breakage.
Store all thermometers at an angle with the bulb lower than the expansion chamber. VWR International offers two storage trays with a built in angle for proper storage.

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Fact # 2: In the event of separation, thermometer liquid can be reunited

Solution:
Our reuniting instructions can help get your thermometer up and working again in no time (Always wear safety glasses & gloves):

Cooling Method:

1. Prepare a solution of shaved ice and salt or CO2 (dry ice) and alcohol
2. Place the thermometer bulb in the solution, keeping the thermometer upright
3. Allow the liquid column to retreat into the bulb
4. Swing the thermometer (bulb down) in an arc, forcing the trapped gas to rise above the column
5. Allow the thermometer to warm slowly in an upright position

Heating Method:

1. Heat the thermometer bulb in an upright position in warm liquid, warm air, or over a flame
2. Allow the liquid column to rise until the separated portion of the column enters the expansion chamber (NOTE: Over-filling the expansion chamber will break the thermometer)
3. With the thermometer in an upright positions, gently tap it allowing the gas separating the column to rise above the column
4. Allow the thermometer to cool slowly in an upright position

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Fact # 3: If not used properly, thermometers can give inaccurate readings

Solution:
Total immersion thermometers must be immersed to the level of the liquid you are measuring. Whereas partial immersion thermometers must be immersed to the line marked on the thermometer.*
If total immersion thermometers are used at partial immersion depths (or vice versa), inaccuracies will occur. These inaccuracies increase as the temperature increases.

* In a rare case you need to use a partial immersion thermometer in a total immersion application, corrections for emergent stem must be obtained to achieve an accurate reading.

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Fact # 4: Calibrated and certified thermometers are not the same

Solution:
All thermometers are calibrated, but not all thermometers are certified. In order to manufacture a thermometer, the instrument must be calibrated against a reference standard. Calibration during manufacturing establishes the guidelines for line and number placement. If a thermometer is certified this means that after the instrument is manufactured, it is once again individually calibrated against a reference standard at a specific point of points along the scale. The results of this special second calibration are recorded on an official report from the manufacturer. This report accompanies the certified thermometer when purchased.

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Fact # 5: Thermometers may need to be recalibrated; does yours need it?

Solution:
There are several reasons why thermometers may need to be re-calibrated:

1. ISO 9000, Quality Control, and other regulations require Reports of Calibration for thermometers
2. Reports of Calibration with corrections allow one to calibrate or check other thermometers within certain tolerances
3. There is a need to know how accurately a thermometer is reading or if it is still accurate to specifications
4. There is a need to know, for an application, what the thermometer is reading to a high degree of accuracy or between divisions.

VWR International offers a very successful calibration program. Call 1-800-HELP-VWR for details.

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Fact # 6: Thermometers come with a variety of liquid options, which can get confusing

Solution:
Mercury: Metal, molecular formula: Hg, an odorless, silvery liquid with metallic luster

Mineral Spirit: Petroleum hydrocarbon, clear odorless liquid with a petroleum odor, usually mixed with blue, red or green colored diazo dye.

Enviro-Safe®: A mixture of biodegradable citrus oil (hydrocarbon) and a green, non-toxic dye (Monoazo-Anthroquinone Dye). This is 100% non-toxic • non-hazardous • biodegradable liquid.

Mercury/Thallium Amalgam: Lowers the freezing point of mercury to below -40°C by lowering the mercury solidification point.

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Fact # 7: Sometimes contamination of any sort can be detrimental to your sample

Solution:
Teflon is a special material developed by E.I. Dupont de Nemours Company. Teflon coating involves encapsulating a thermometer within a thin layer of Teflon. Since the material is transparent when applied, you are still able to read the thermometer scale and liquid column. The main purpose of Teflon coating is safety. Once a thermometer is coated it becomes less sensitive to breakage. In the event that the thermometer does break, the liquid in the thermometer and the glass itself is contained within the Teflon. This reduces the hazards if the thermometer liquid is mercury.
Teflon coating does not affect the accuracy of a thermometer. But Teflon may slow the response time of the liquid column to reach equilibrium temperature. Teflon-coated thermometers are not recommended for applications involving timed tests.
Any glass thermometer can be Teflon coated if its range does not exceed 260°C.

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Fact # 8: Conversions are simple

Solution:
For °F to °C and vice versa:

°F = 9/5 °C + 32
°C = 5/9 (°F - 32)

For the most common thermometer lengths:
203 mm = 8" in length
305 mm = 12" in length
405 mm = 16" in length

For inches to mm:
Multiply total inches by 25.4
ex: 8" x 25.4 = 203.2 mm

For mm to inches:
Divide total mm by 25.4
ex: 203 mm / 25.4 = 7.99"

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Fact # 9: If you have any further questions we are just a phone call away

Solution: Call 1-800-TEST-LAB and we will answer all of your thermometer needs.

Download our printable quick reference PDF, which views with the Adobe® Acrobat Reader.

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