Mercury or red fluid in thermometer?

NeoPTLD

Platinum Member
Nov 23, 2001
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Is one better over the other for general purpose use?

I was looking through VWR catalog and they offer both mercury and red fluid types for the same range for similar price. Usually mercury is more costly, but it's the opposite in this case. They're charging a lot more for yellow back version compared to white back and I think that explains it has to do with inventory/demand than anything.


they're both 1°C division, -20 to 110°C

look at 61066-104. Spirit filled $9.48

look at 61013-028 mercury filled $8.02
 

Cogman

Lifer
Sep 19, 2000
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get the mercury, it is funner to play with if it breaks :). But dont get it if you have little kids that will eat it. The red stuff is alcohol (if I remember Right) and so it is not enough to hurt you if you drank it. Mercury IMHO is easier to see then the red stuff.
 

LurchFrinky

Senior member
Nov 12, 2003
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Another vote here for the mercury. Although they probably have improved, I remember seeing colored thermometers with bubbles in them. The surface of the mercury is always very well defined and will be easier to see IMO.
 

rjain

Golden Member
May 1, 2003
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I think mercury is also more reliable as far as the density being more linear with temperature.
 

f95toli

Golden Member
Nov 21, 2002
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Mercury is also very toxic and is an enviromental hazard. I read somewhere it will become illigal to use mercury in thermometers in the EU (it is already illegal to produce new thermometers), I can't say I miss it.
Why do you need it? Why not simply use an electronic thermometer?
 

ebaycj

Diamond Member
Mar 9, 2002
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yeah. get one of those ear-gun style electronic thermometers that takes your temp in 1 second... don't waste your time with alcohol or mercury thermometers...

ebaycj
 

Cogman

Lifer
Sep 19, 2000
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I would not use an ear-gun But they do have some electronic ones that are fairly good (like in 0.01 of a degree F).
 

NeoPTLD

Platinum Member
Nov 23, 2001
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Originally posted by: ebaycj
yeah. get one of those ear-gun style electronic thermometers that takes your temp in 1 second... don't waste your time with alcohol or mercury thermometers...

ebaycj

I'm not talking about fever thermometers.
 

RossGr

Diamond Member
Jan 11, 2000
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<FONT style="BACKGROUND-COLOR: #fffff0">In general a thermocouple will do a better job then a column thermometer. A theromcouple has very better accuracy, and lower thermal mass for quicker measuments. Of course it is necessary to have some electronics to use a thermocoulple. If you need to record any data the a thermocouple and an A/D card are the best way to go.
Edit:
I just noticed you price range, for monitering house and yard temp you can get a cheap digital at Radio Shack.

ReEdit:

Hey all that font *rap doen't show up in the edit window!
</FONT>
 

illusion88

Lifer
Oct 2, 2001
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save the trouble if and when it breaks, go with the red one. It might be a little harder to see, but the results are the same. Just stick a white peice of paper behind it before taking your reading.

This way, when you break it, at least you aren't harming the envioment that tiny tiny tiny bit.
 

Mingon

Diamond Member
Apr 2, 2000
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The mercury in most thermometers is actually not that dangerous, its a bit of a wives tale. Whilst not a good idea to ingest it is so dense it will normally past straight through.
 
May 26, 2001
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the problem with digital thermometers is that you have to calibrate them, usually meaning that you have to use a fluid thermometer anyways...
 

Particle Man

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Oct 9, 1999
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Mercury is dangerous. It releases vapors over time that can be inhaled by the lungs and cause heavy metal poisoning (very elongated time frame). Ingesting it will certainly cause heavy metal poisoning, not to mention about the large amount of hydrogen gas that you would produce (Hg(l) + 2HCl --> HgCl2 + H2(g)). Finally, mercury can be absorbed through the skin (mad hatter's disease). Mercury cannot be removed from your body once it is in your system. It is an accumaltive metal that will stay with you forever. You can't sweat it out or even get rid of it through blood transfusions. It is a nasty way to die once you have reached the critical level. Granted that the human body is able to handle a lot of toxins depending on one's mass/weight, this one element that is known for many neurological problems.

Alkylated mercury is the worst. This has cause deaths in the sciences, especially within chemistry. Dimethylmercury (Me2Hg) used to be a standard for instruments until a professor died in the northeast. The professor used standard gloves (nitrile) and a drop of Me2Hg was spilled on the worn glove. The Me2Hg passed through the glove, the skin barrier and finally into the bloodstream. The professor died a cruel punishing death.

For safety sake, use the mineral spirits thermometer if you are in a univeristy. Industry and government already has put strong regulations on mercury thermometers.
 

brentkiosk

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Oct 25, 2002
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Mercury thermometers are usually a little better than alcohol. Alcohol is more likely to separate if the thermonmeter is not stored upright. BUT, do not get mercury for general purpose use. It is toxic and dangerous. Someday, you or someone will want to dispose if it, and that won't be easy. I have a bunch of boty Hg and alcohol thermometers at work - they aren't from VWR but same sort of thing. The alcohol ones are absolutely, completely satisfactory for general purpose work.
 

LurchFrinky

Senior member
Nov 12, 2003
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Originally posted by: Particle Man
Ingesting it will certainly cause heavy metal poisoning, not to mention about the large amount of hydrogen gas that you would produce (Hg(l) + 2HCl --> HgCl2 + H2(g)).
Well, the rest of your post seems reasonable enough, but I wasn't aware that hydrochloric acid was present in the human body. I may be wrong, but I would think that anything that reactive would already have combined into lower energy molecules.

 

NeoPTLD

Platinum Member
Nov 23, 2001
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Originally posted by: Particle Man
Ingesting it will certainly cause heavy metal poisoning, not to mention about the large amount of hydrogen gas that you would produce (Hg(l) + 2HCl --> HgCl2 + H2(g)). Finally, mercury can be absorbed through the skin (mad hatter's disease).

Mercury doesn't react with HCl or other non oxidizing acids. Mad hatter's disease have been attributed to mercuric nitrate, a soluble salt of mercury.

Alkylated mercury is the worst. This has cause deaths in the sciences, especially within chemistry. Dimethylmercury (Me2Hg) used to be a standard for instruments until a professor died in the northeast. The professor used standard gloves (nitrile) and a drop of Me2Hg was spilled on the worn glove. The Me2Hg passed through the glove, the skin barrier and finally into the bloodstream. The professor died a cruel punishing death.

Soluble compounds of mercury are often toxic, but it's ludicrous to say avoid using metallic mercury because you gave an example of one of the most toxic mercury compound. Mercury metal isn't all that toxic.

This is like saying we need to avoid carbon, nitrogen and hydrogen all together, because hydrogen cyanide, HCN is highly toxic.


I wasn't asking for a safety lecture. In this discussion, we're going to focus on the functionality of the thermometer in its unbroken state.

As you can tell from the links provided, those two types(red fluid and mercury filled) are supposed to have the same the same performance.

Well the usability problem with mercury is that it's really hard to read, because the column is much thinner and contrast isn't as good.
 

uart

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May 26, 2000
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NeoPTLD is 100% correct about elemental Mercury (as used in thermometers) being very much less toxic than organic Mercury compound, this much is beyond any dispute. Just the same it's good pratice to be very careful with Mercury thermometers and their disposal.

One other fallacy posted above is that ingested Mecury is never excreted. Ingested elemental Mercury will mostly pass straight through the digestive track with only a small amount of absorbsion. That is, by far the majority will be excreted before it is ever even absorbed. (Dont try it though, as even a small amount of absobed Mercury is still dangerous to your health). Once absorbed by the body it will cause elevated mecury levels in the blood and organs and this will infact result in increased excretion of the toxin, albeit rather slowly. So if you have a single exposure to a heavy metal toxin (like Mecury or Lead) then are removed from the source of exposure then your body level will gradually decrease over time and eventually return to normal. The time taken depends largely on how you define "normal" however and it may take many months or even years to reach a given "normal" level.


Mercury is dangerous. It releases vapors over time that can be inhaled by the lungs and cause heavy metal poisoning (very elongated time frame).
While I disagreed about the part about Mecury never being removed from the body I must stress that the part about the vapour being dangerous is very true. This is the main reason to be careful with a mercury thermometer. Say for example you dropped and broke one in your bedroom and didn't clean up the spilt Hg properly (which can be very difficult to do as it can run into cracks etc). This would cause a small amount of mecury vapour to be released over a long time period and would probably result in a small elevation of you body mecury levels over time, particularly if you spent a lot of time in that room without good ventilation
 

EmMayEx

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Mar 2, 2001
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Originally posted by: uart
NeoPTLD is 100% correct about elemental Mercury (as used in thermometers) being very much less toxic than organic Mercury compound, this much is beyond any dispute. Just the same it's good pratice to be very careful with Mercury thermometers and their disposal.

One other fallacy posted above is that ingested Mecury is never excreted. Ingested elemental Mercury will mostly pass straight through the digestive track with only a small amount of absorbsion. That is, by far the majority will be excreted before it is ever even absorbed. (Dont try it though, as even a small amount of absobed Mercury is still dangerous to your health). Once absorbed by the body it will cause elevated mecury levels in the blood and organs and this will infact result in increased excretion of the toxin, albeit rather slowly. So if you have a single exposure to a heavy metal toxin (like Mecury or Lead) then are removed from the source of exposure then your body level will gradually decrease over time and eventually return to normal. The time taken depends largely on how you define "normal" however and it may take many months or even years to reach a given "normal" level.


Mercury is dangerous. It releases vapors over time that can be inhaled by the lungs and cause heavy metal poisoning (very elongated time frame).
While I disagreed about the part about Mecury never being removed from the body I must stress that the part about the vapour being dangerous is very true. This is the main reason to be careful with a mercury thermometer. Say for example you dropped and broke one in your bedroom and didn't clean up the spilt Hg properly (which can be very difficult to do as it can run into cracks etc). This would cause a small amount of mecury vapour to be released over a long time period and would probably result in a small elevation of you body mecury levels over time, particularly if you spent a lot of time in that room without good ventilation

For adults metallic mercury is not particularly toxic. Historically it was taken internally to alleviate constipation but then these are the same physicians that relied on bloodletting as a mainstay treatment. Still, if ingesting mercury were potentially fatal you'd think they'd have stopped using it after the first few patients keeled over. More recently it has been widely used as an amalgam with silver for filling cavities in teeth. After many decades of use and there is no evidence I am aware of that the trace levels that abrade from fillings over time pose any health threat. In fact many dentists prefer mercury amalgam fillings as they are more durable and have fewer problems than other formulations. There is some evidence that high mercury levels can cause developmental problems in animals but the level at which this occurs in humans is not known as there is very little data. I guess not many people are offering up their kids for the good of science these days :p. This uncertainty is why authorities completely freak out when some is discovered loose in a school (i.e. Benjamin Tasker Middle School in Washington DC about a month ago).

Mercury vapor can be a problem but mercury has a very low vapor pressure so you have to heat it up quite a bit (i.e. with a flame) to receive a significant dose. It is very unlikely that droplets of metallic mercury pose a significant health threat to anyone even in a frequently occupied poorly ventillated room. Mercury barometers (which have pools of mercury exposed to the air) have been used for centuries and you don't hear about mercury poisioning syndromes among weather forcasters they way you do about hat makers (mad hatters disease).

The problem is that we can readily detect the stuff at astoundingly low concentrations (parts per trillion or better) and nobody can ever certify a particular level as 100% safe so certain segments of the population demand zero exposure which is practically impossible (especially with coal fired power plants evaporating tons of the stuff every year).

Getting back to the original question I'd vote for mercury. All of the NIST traceable certified sets of thermometers I'm aware of are mercury filled. I don't believe there are any NIST traceable electronic temperature standards, they are generally calibrated against mercury thermometer standards or one of the standard temperature references (like water at it's triple point of the freezing point of platinum). I think the low vapor pressure and high volumetric density of mercury makes is the best thermometric fluid around. This is why in spite of toxicological zealots' best efforts they are still making mercury thermometers.

Max L.

 

Particle Man

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Oct 9, 1999
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You are correct about elemental mercury, NeoPTLD and uart. I was thinking about nitric acid and mercury. My error.

Anyway, the safety thing is in most institutions, and I was more on the lines of thinking about your position when you have to answer to OSHA. It is like hell when OSHA pays a visit and have to answer to your superiors. I assume that you are within a fairly well protected enviroment to not worry about this.

In the lines of your original question...
The mineral spirits thermometers are easier to read than the mercury, however the mercury thermometers tend to be more accurate (if precision is needed within 0.01C) than the mineral spirits, in the exception of extremely low temperatures (< -78C). It seems that there are always bubbles, gaps or discontinuities with either type of thermometer. From experience, the mineral spirits thermometers are easier to work around this problem with a low temperature bath. The glass at the bulb is very thin and can break for either type, however mercury seems to be more sensitive to the lower temperature extremes in comparison to mineral spirits.
 

gsellis

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Dec 4, 2003
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If air transport is required, remember that Hg is considered a hazardous material.