What is the "blue spirit" (or "red spirit") in mercury-free thermometers?

Question

I surmise it's some kind of alcohol, but is there a standard chemical used for these?

One of them just exploded in my students' lab! It was the kind with blue fluid in it.

exploded, as in "ignited/fireball" or as in "overheated and glass broken due to pressure"? — dlatikay, Mar 03 '18 at 18:01
@dlatikay the latter. Loud pop. No combustion that I know of — khaverim, Mar 03 '18 at 18:25

score 16 · Accepted Answer · edited Mar 03 '18 at 10:17

16

As per the Wikipedia page on Spirit Thermometers:

The liquid used can be pure ethanol, toluene, kerosene or isoamyl acetate, depending on manufacturer and working temperature range. Since these are transparent, the liquid is made more visible by the addition of a red or blue dye.

1,4-bis(butylamino)anthraquinone - commonly known as "Oil Blue 35" - may possibly be used as the blue dye.

edited Mar 03 '18 at 10:17

Gaurang Tandon

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answered Mar 02 '18 at 15:33

Avyansh Katiyar

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score 13 · Answer 2 · edited Mar 03 '18 at 10:19

13

Another organic solvent used may be pentane. Perhaps the common ones contain toluene dyed with a red aniline dye .

Other spirit filled thermometers variants include:

Blue fill contains isoamyl benzoate;
Red fill may contain kerosene or pentane with aniline dye

Aniline red

_Credits

Acknowledgements

Spirit-Filled Glass Thermometers: Document

edited Mar 03 '18 at 10:19

Gaurang Tandon

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answered Mar 02 '18 at 16:52

xavier_fakerat

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What is the "blue spirit" (or "red spirit") in mercury-free thermometers?

2 Answers2