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Author: Subject: Thermometers: alcoholic vs. Hg filling
dangerous amateur
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[*] posted on 27-10-2020 at 07:10
Thermometers: alcoholic vs. Hg filling


I just dropped my last glass thermometer I used for almost everything.

I was about to order some glass stuff from a laboratory shop anyway.

Now they have two types:
One has an alcohol based filling, one has mercury.
The alcoholic version is said to be "fully submerging", the mercury version has a minimum dept of 70mm.


Since the mercury version is only slightly more expensive and seems to be superior - that would be my choice.

Any objections?
What would you prefer and why?


Measuring a liquid in a small beaker with 30mm filling height with a 300mm thermometer that should be fully submerged will lead to errors, I'm aware of the situation. However, do you have some experience about the extent of error one can expect? For some 60°C in the beaker, 18°C air, no wind, or some other example situation you can think of?


My question here is, what amount of error would
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teodor
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[*] posted on 27-10-2020 at 07:25


Is it ever dependent on the filling type? I have not Hg thermometer with the scale up to 250C but on 131 (iso-amyl alcohol boiling temp) the error is already 8 degrees when the submerged part is equal to the mark 90-100C. On 100 it is 3 degrees but below 90 (in the submerged part) there is no error.
On the other hand I have a thermometer with NS14/23 ground glass joint (so, the submerge point is constant) and it doesn't require correction.
So, I think it is not dependent on Hg/alcoholic/anything.

[Edited on 27-10-2020 by teodor]

[Edited on 27-10-2020 by teodor]
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DraconicAcid
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[*] posted on 27-10-2020 at 08:28


I figure the alcohol one is going to be less hassle to clean up when I eventually break it.



Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Herr Haber
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[*] posted on 27-10-2020 at 11:21


I bet one is jacketed with the writings inside and the other one is not and has the writings outside.

One you can put in a beaker full of acid, the other one will lose all it's writing and should be kept for distillations.




The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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valeg96
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[*] posted on 27-10-2020 at 13:33


I have plenty of vintage Hg thermometers found at a flea market for 1€/each, but out of curiosity I've also purchased a bunch of those cheap Hg lab ones you can find on aliexpress.

They seem to be pretty accurate (±1°C, you can tell while distilling stuff), though they can develop bubbles if improperly used. If you have a very small budget consider purchasing those.





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itsallgoodjames
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[*] posted on 27-10-2020 at 13:40


Quote: Originally posted by DraconicAcid  
I figure the alcohol one is going to be less hassle to clean up when I eventually break it.

I use alcohol ones for this exact reason. I tend to break a lot of thermometers, and mercury ones are a pain to deal with if you break them. If you're at all likely to break it, go with the alcohol one. They're so much easier to clean up




Nuclear physics is neat. It's a shame it's so regulated...

Now that I think about it, that's probably a good thing. Still annoying though.
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Mateo_swe
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[*] posted on 27-10-2020 at 14:20


What about the very cheap Type K Thermocouples that come with a small display.
Are those not accurate enough?
If one put the sensor in a glasstube sealed in one end they would have about the same diameter as a normal lab thermometer.


K-type_small.jpg - 23kB
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itsallgoodjames
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[*] posted on 27-10-2020 at 14:30


Quote: Originally posted by Mateo_swe  
What about the very cheap Type K Thermocouples that come with a small display.
Are those not accurate enough?
If one put the sensor in a glasstube sealed in one end they would have about the same diameter as a normal lab thermometer.



I've been planning to switch to one of those for a while now, I've heard some pretty good things about them. Plus you can hook them up to an Arduino to monitor your reactions which would be nice.




Nuclear physics is neat. It's a shame it's so regulated...

Now that I think about it, that's probably a good thing. Still annoying though.
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Dr.Bob
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[*] posted on 27-10-2020 at 14:35


Mercury ones are better on wide ranges of temps. Alcohol ones can do lower temps better, and are safer and easier to ship. Just depends on what you want to do. I use both, but mostly non-Hg ones at work. If people in the US need therms, I still have a few of both types, in several ranges and types. But too hard to ship overseas, due to many regs. Even in the US, Hg ones can only be shipped by FedEx easily.
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dangerous amateur
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[*] posted on 28-10-2020 at 11:02


Thanks.


Quote:

I bet one is jacketed with the writings inside and the other one is not and has the writings outside. One you can put in a beaker full of acid, the other one will lose all it's writing and should be kept for distillations.

I think the scale is inside the thermometer.
I once had one with the number on the outside and yes, the once in acid the paint was gone;)

I'll go for mercury. I dont plan to break it:P

On the long run a thermocouple would be more useful, but I postponed that.

[Edited on 28-10-2020 by dangerous amateur]
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