Mercury-free oral thermometers

It’s hard to find a reliable oral thermometer these days.  I’m wary of the accuracy of the digital ones, and often, when I buy them, the battery is already dead. However, I was recently in a Rite-Aid Pharmacy, and they were selling an “environmentally friendly” mercury-free oral thermometer.  This piqued my interest, so I decided to buy one.


As it turns out, in place of mercury, they are using a substance called Galinstan®, which they claim is non-toxic.  According to Wikipedia, Galinstan is a family of eutectic alloys mainly consisting of gallium, indium, and tin, which are liquids at room temperature, typically freezing at −19 °C (−2 °F).  Wikipedia goes on to say:

Galinstan is commercially used as a mercury replacement in thermometers due to its nontoxic properties, but the inner tube must be coated with gallium oxide to prevent the alloy from wetting the glass surface.

After searching the web a bit, I could not find anything particularly heinous about gallium oxide to suggest that its presence in the thermometer is necessarily a bad thing.  The full MDSD (Material Safety Data Sheet) on Galinstan can be found here.

The thermometer is made by a company called Geratherm A.G. that also makes digital and infra-red thermometers.  Leave it to the Germans to develop this cool technology.

Although the EPA has not banned mercury thermometers, they do provide this helpful information page about mercury.  Apparently 13 states have individually banned the sale of mercury-containing thermometers, and I was surprised to see that Vermont was not on that list.  I could not find any mercury-containing oral thermometers for sale online, so I think manufacturers are simply not selling them at all.

Thermometers 2011I decided to give this thermometer a test drive to see how its results compare to those of a digital thermometer.  I did 3 trials with each thermometer to make sure each one gave consistent results.  With the Geratherm thermometer, I got 98.7, 98.7 and 98.6.  Clearly, it is consistent.  With the no-name digital thermometer, I got 98.6 during each trail.

It looks like I don’t have a fever, but I do have two fully functioning mercury-free oral thermometers.  The thermometer with the Galinstan seems to work great, and I would highly recommend it for someone who doesn’t like digital thermometers.  Having to flick the “mercury” down in the thermometer brings back fond memories of my mom taking care of me when I was little, so the Galinstan thermometer also appeals to my sense of nostalgia.

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