Disagreements in published boiling temperatures of tin, gallium etc.

[Peter Dow]

I have noted big disagreements of a scale of hundreds of degrees centigrade in published values for the boiling temperature of chemical elements such as tin and gallium.

 

For example,

 

Tin

Wikipedia - 2602 °C, 2875 K, 

Chemical Elements website - 2270.0°C, 2543.15 K

which agrees with one of my text books

Penguin Dictionary of Chemistry - 2270°C

but not the other

Chemistry, Molecules, Matter and Change - 2720°C

 

 

Gallium

Wikipedia - 2204 °C, 2477 K, 

Chemical Elements website 2403.0 °C, 2676.15 K

which agrees with one of my text books

Penguin Dictionary of Chemistry - 2403 °C

but not the other

Chemistry, Molecules, Matter and Change - 2070 °C

 

 

Of course I am wondering why the different values - errors by the authors of books or websites or genuine disagreements between scientists as to the values?

 

Which source do people recommend as the most reliable source of accurate boiling temperature information and why?

[D H]

My CRC handbook of chemistry and physics says 2270°C for tin, 2403°C for gallium. A lot of MSDSs specify a value of 2507°C for tin (yet another value), and 2400°C or 2403°C for gallium.

 

Books and websites are not perfect. Errors propagate like the childhood game of telephone. In the case of tin, wikipedia does not cite the source of their physical data. Who knows where that number came from?

[mississippichem]

Some of those mid p-block elements display messy boiling/melting ranges instead of nice discrete values. If you're looking for a hard number for a calculation or a report, I would go with D H's CRC handbook. Many professionals hold the CRC handbook as the standard for physical values and constants. Just to make sure though, see if some of those values you gave also have a reported pressure as that might alter the boiling point significantly.

[Peter Dow]

My CRC handbook of chemistry and physics says 2270°C for tin, 2403°C for gallium.

CRC claim tin boils at a lower temperature than gallium?!

 

A lot of MSDSs specify a value of 2507°C for tin (yet another value), and 2400°C or 2403°C for gallium.

Another source derived from an old publication I remember being on the same shelves as the CRC handbook back in the days when I used the library is NPL's Kaye and Laby which gives 2620°C for Tin and 2200°C for Gallium but most of their temperatures they only quote to the nearest 10°C.

 

Temperatures at the boiling point depend on pressure so if the temperature is measured while the metal or whatever is boiling in an enclosed vessel this would effect the boiling point temperature. However, the pressure is not specified most often and I am left to guess that it might be atmospheric pressure.

 

Books and websites are not perfect. Errors propagate like the childhood game of telephone.

 

I appreciate that. For example, maybe the author or publisher for "Chemistry, Molecules, Matter and Change" book swapped the 7 & 2 around and put in "2720°C" instead of "2270°C" which seems to be a more popular value?

 

In the case of tin, wikipedia does not cite the source of their physical data. Who knows where that number came from?

I have raised the matter on the Wikipedia discussion pages for Tin and Gallium so we will see what Wikipedia has to say for themselves on this in due course perhaps.

 

It would be nice if there was a definitive source for the world scientific and engineering community, an organisation which prides itself on knowing it has the right values and referenced chapter and verse of all those had measured the value and how.

 

There are a lot of websites out there, science-for-the-people websites, but with advertising on them, which are very happy to quote a value for this or that without themselves having any knowledge of how and where the value is derived. These sites are copying the information from somewhere, anywhere, sticking an advert on their page to make some money yet not being all that useful in reality.

 

However, in this case, the values in books I remember reading long before the internet was around seem to disagree significantly on these boiling temperature values as well.

 

NPL's Kaye and Laby which gives 2620°C for Tin and 2200°C for Gallium but most of their temperatures they only quote to the nearest 10°C.

Kaye and Laby does not even agree with itself between one table and another, especially for Tin though the values for Gallium are close enough.

 

In another table, Kaye & Laby. 3.10.1 Standard molar heat capacities and properties of melting and evaporation of the elements they quote a normal boiling temperature Tvap for

 

Tin (Sn) of 2990K which I make 2717°C and for

Gallium (Ga) 2480K which I make 2207°C

 

which is different from the their table 3.1.2 Properties of the elements value for

Tin of 2620°C and for

Gallium 2200°C.

 

Some of those mid p-block elements display messy boiling/melting ranges instead of nice discrete values.

I heard that some elements and chemicals exhibit dynamic supercooling / superheating phenomena but I had not heard that there wasn't always a definitive temperature which defines a stable phase transition.

 

I see a mess in the assortment of published data but I am more likely to attribute that mess to us scientists doing a less than perfect job rather than to matter not being sure at what temperature it wants to boil at.

 

If you're looking for a hard number for a calculation or a report, I would go with D H's CRC handbook.

Well if you are interested I was drawing a bar chart with the temperature of the liquid phase for the elements of galinstan. This is what I have got so far based on the wikipedia values.

 

 

There seems to be little data available regarding the boiling point or dissociation temperature of galinstan but before I can consider that question properly I need to consider why the published values for the boiling points of Tin and Gallium vary from one source to another.

 

 

Many professionals hold the CRC handbook as the standard for physical values and constants. Just to make sure though, see if some of those values you gave also have a reported pressure as that might alter the boiling point significantly.

Hmm but then many professions do not use the CRC handbook I suppose. In any case, I have never assumed that what "professionals" do routinely should just be accepted without challenge. As scientists we seek the truth not to follow the crowd.

Edited November 10, 2010 by Peter Dow

[Peter Dow]

My CRC handbook of chemistry and physics says 2270°C for tin, 2403°C for gallium. A lot of MSDSs specify a value of 2507°C for tin (yet another value), and 2400°C or 2403°C for gallium.

 

Books and websites are not perfect. Errors propagate like the childhood game of telephone. In the case of tin, wikipedia does not cite the source of their physical data. Who knows where that number came from?

Your CRC handbook values seem to agree exactly with the Penguin Dictionary of Chemistry therefore one may be copying the other or both using the same source.

 

Wikipedia have a page where they name references for boiling points.

 

However, the data values tabulated on that wikipedia page do not seem always to have been copied accurately from the reference sources. There is an associated discussion page wherein I am pointing some of this out to wikipedia editors.

 

My CRC handbook of chemistry and physics says 2270°C for tin, 2403°C for gallium.

Well here is a curious thing. A chap on wikipedia says he has checked his 89th edition of the CRC handbook of chemistry and physics and he says that it states "2204 degrees C (2477 K)" for the boiling point of gallium.

 

So I am wondering if you, D H, are looking at a different table in the same book? I have already pointed out that Kaye and Laby gives two different values for the same property in two different tables. What is the heading and section number of the table in the CRC handbook from which you are reading "2270°C for tin, 2403°C for gallium" from?

 

Or perhaps your edition of the CRC handbook is not the 89th but a different edition and the value has changed between editions?

 

Can you, or anyone, help to clear this up please?

Edited November 10, 2010 by Peter Dow

[John Cuthber]

If someone gives me a lot of money I will clear the confusion up for you all; but it will need to be a lot of money

Seriously, that's probably the root of the problem. It's frankly rather difficult to measure temperatures in this range. Making clean systems containing boiling metals at atmospheric pressure, but in the absence of air to avoid reaction, is even harder.

I'd love to be able to say "never trust a measured value unless it has an uncertainty stated along with it" but that would grind most things to a halt.

[D H]

Seriously, that's probably the root of the problem.

That, plus a who cares? factor. All atomic elements have some boiling point, so for completion's sake a value is included in all of these chemical properties tables even if nobody cares. If the boiling point of tin or gallium had some financial interest there would be a push to reconcile those wildly varying values. That you do see wildly varying values is a sign that the value is of very little interest and limited value.

 

 

 

[Peter Dow]

That, plus a who cares? factor. All atomic elements have some boiling point, so for completion's sake a value is included in all of these chemical properties tables even if nobody cares. If the boiling point of tin or gallium had some financial interest there would be a push to reconcile those wildly varying values. That you do see wildly varying values is a sign that the value is of very little interest and limited value.

Well you cared enough to post in this topic, for which I thank you.

 

I wonder if you could have a look for a second table in your CRC handbook which also gives (different) values for boiling points of the elements. Perhaps there is a "chemistry" table and a "physics" table? Is there? If not which edition is your CRC handbook?

[John Cuthber]

That, plus a who cares? factor. All atomic elements have some boiling point, so for completion's sake a value is included in all of these chemical properties tables even if nobody cares. If the boiling point of tin or gallium had some financial interest there would be a push to reconcile those wildly varying values. That you do see wildly varying values is a sign that the value is of very little interest and limited value.

Not so much who cares, but who cares enough to pay.

On the other hand, the triple point of gallium is known to about 9 digits.

[D H]

Not so much who cares, but who cares enough to pay.

On the other hand, the triple point of gallium is known to about 9 digits.

I could have said "Is there any value in knowing the boiling point of tin other than the obsessive-compulsive academic interest of filling in an unknown number on a table?". That was too long, so I said "who cares?" instead.

 

Scientists know the triple point of gallium to about 9 digits because knowing that value to a high degree of precision apparently has a lot of monetary value. That science only knows the boiling point of gallium to one or two digits is a good test of how much anyone cares about knowing that value.

 

I suspect those chemical tables are chock full of imprecise values. Would improving those be worthy of a thesis? Probably not. Who cares?

 

[mississippichem]

How does one measure temperature above the boiling point of mercury anyway?

[Peter Dow]

A discussion on wikipedia on the boiling point of gallium seems to indicate that the CRC handbook editions list the following values for the boiling point of gallium -

 

• 47th to the 66th editions - 2403°C
  
• 84th and later editions - 2204 °C
  

Perhaps D H will finally tell me the edition number of his CRC handbook he quoted from above?

 

My suggestions as to why measured boiling points vary so much

 

Superheating of the liquid

We know that gallium supercools readily so why cannot it also superheat? Perhaps experimenters are in too much of a hurry to measure the boiling temperature and keep raising the temperature too quickly without waiting for the superheated liquid to boil which it will do eventually at a lower temperature?

 

Differences in pressure

If anything genuinely changes a boiling point temperature it is pressure. Perhaps experiments have not taken care to ensure the heated liquid is under standard pressure conditions?

 

Simple experimental error

Temperature measuring devices may have been wrongly calibrated or misread?

 

Chemical contamination of the sample

Gallium is considered to be very reactive at high temperature. Perhaps the samples are reacting with the vessel and the contaminants are modifying the boiling temperature?

 

How does one measure temperature above the boiling point of mercury anyway?

Start here - http://en.wikipedia.org/wiki/Temperature_measurement

 

Galinstan, an alloy of gallium, indium and tin, is a non-poisonous mercury-substitute for thermometers.

 

The glass of the thermometer would melt before galinstan boils or dissociates. Galinstan is a much "cooler" liquid metal than mercury. B)

 

For measuring the sort of temperatures under discussion here (2000 plus degrees C) perhaps a pyrometer of some kind.