Galileo Thermometer alternative tags and vials

[Erina]

Receiving a Galileo Thermometer for Christmas this year I was unimpressed by the range of which the internal vials reacted to the ambient temperature. Some research on the matter led me to to understand that the density of the liquid in the vials is uniform, only the tags with the temperature inscription vary and so it should be trivial to adjust the temperatures they react to.

I say trivial, but that would involve emptying the surrounding solution and that would be beyond my ability. However, I would care to know if there is an outlet in the UK/EU of whom sell vials, or the tags themselves, that react to the a temperature range from zero to eighteen degree celsius?

Alternatively, what would the tags be made from and what would be the specific weights to temperature need to be, if worst comes to the worst and I have to mill some of my own?

Edited January 2, 2020 by Erina

[swansont]

The tags can probably be made of anything that will survive without corroding

The thermometer bobs I've seen are blown glass and wouldn't be adjustable by themselves. Their average density is adjusted by the amount of weight in the tag, so that the vial has the proper buoyancy at the chosen temperature. You can either change the weight of the tag, or the number it displays.

[Erina]

I think that the surrounding solution is a mix of water an ethanol as it conducts to the heat better than just water.

I found the following to be suggested as to be less reactive alloy metals than most: Pt, Rh, Pd, Os, Ru, Ir, Ti, it would just be a matter of finding the cheapest.

As all of the vials contain the same liquid density (I don't know what that solution is inside the vials?) then I could modify the range of reaction, but what are the weights for each temperature?

Edited January 3, 2020 by Erina

[swansont]

9 hours ago, Erina said:

I think that the surrounding solution is a mix of water an ethanol as it conducts to the heat better than just water.

I found the following to be suggested as to be less reactive alloy metals than most: Pt, Rh, Pd, Os, Ru, Ir, Ti, it would just be a matter of finding the cheapest.

As all of the vials contain the same liquid density (I don't know what that solution is inside the vials?) then I could modify the range of reaction, but what are the weights for each temperature?

If that's correct about the vials being uniform (I would expect some variation, but uniform is a reasonable initial assumption) then you would have to look at the density of water (or the ethanol+water mix) as a function of temperature.

https://hypertextbook.com/facts/2007/AllenMa.shtml

For water the variation is small, about 5% between 10 ºC and 30 ºC, but it's pretty linear

Then it's a matter of matching the density of a vial to a temperature.

[Erina]

As my present it a factory issued product and I have no contact with the manufacturer so I cannot be sure of the water to ethanol ratio, and as I cannot get access to it then it matter even less. I was just hoping that there was a standard table with this already measured? It will be a process of trial if and when I make my own.

I would like to know what the liquid is inside the vials, any idea? I thought about pigmenting my own with a thermo-chromatic solution to better emphasise the heat exchange effect, so that the colour transitions to white, and vice-versa, after having fallen?

Edited January 3, 2020 by Erina

[Erina]

In contact with a thermo-chromatic supplier I get the impression that compound can be fine tuned to different temperatures, although there is a little overlap, it could be tailored to reliably change around ~2ºC, however there is no market for such incremental steps as I would need. This too sounds like another system of which I would need to tinker with..

[John Cuthber]

On 1/3/2020 at 1:39 AM, Erina said:

I think that the surrounding solution is a mix of water an ethanol as it conducts to the heat better than just water.

I doubt that.

Water is one of the best conductors.

https://www.engineeringtoolbox.com/thermal-conductivity-liquids-d_1260.html

However, the driving force of these thermometers is the expansion of the liquid.

Ethanol expands much more than water does. (which makes it easier to get the thermometer to work.)

In particular, near 4C the expansion of water is zero.

It seems to me that it would be easier to use (more or less) pure alcohol. That way you don't need to carefully mix the right concentration every time you make a batch of thermometers..

In principle, you can use Raman spectroscopy to find out what's in the tube without opening it.