Talk:Boiling points of the elements (data page)
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[edit]This page is intended as an authoritative data collection with citation of sources, that may be cited as a central reference by other articles (such as for the chemical elements). Femto 20:01, 18 Mar 2005 (UTC)
Data from references may not have been correctly copied into this data page.
[edit]It has come to my attention that values given for the boiling points of certain elements vary greatly from different reference sources, amounting to differences in some cases of hundreds of degrees centigrade (°C).
However, these wide differences in data values may not have been correctly copied into the table in this page.
I am proposing to organise discussion of these apparent differences by element, concentrating initially on Tin and Gallium.
50 Sn tin
[edit]Liquid tin has no allotropes
[edit]My first discussion point is to challenge the table entry heading which qualifies the entry as "tin (white)".
The allotropes of tin, white and gray, or the other high pressure allotropes refer to tin in the solid form which can assume different crystalline structures. Liquid has no crystalline structure so cannot have different allotropes.
Since this table is considering the boiling point of liquid tin the inclusion of the qualifier "(white)" is inappropriate and ought to be deleted from the heading "50 Sn tin (white)" to leave simply "50 Sn tin".
CRC boiling point for tin
[edit]I can't read this myself right now but someone reported to me the value is 2270°C.
WEL boiling point for tin
[edit]The "WEL" is quoting the Webelements.com value or 2875 [or 2602 °C (4716 °F)] K faithfully. However, we are told on this page that the webelements.com website takes its values in turn from two sources - (1) James & Lord and (2) Kaye & Laby
James & Lord boiling point for tin
[edit]Unknown at this time.
Kaye & Laby boiling point for tin
[edit]Kaye & Laby give two values for the boiling point of tin which can be read online.
(1) Properties of the elements 3.1.2 - the value is 2620°C
(2) Standard molar heat capacities and properties of melting and evaporation of the elements 3.10.1 - the value for Tvap is 2990K. By my calculation 2990K = (2990 - 273)°C = 2717°C.
LNG boiling point for tin
[edit]Unknown at this time.
Other reference sources for the boiling point of tin
[edit]D.W.A. Sharp. Dictionary of Chemistry. Penguin. 2nd Edition
[edit]The value is 2270°C.
L.Jones & P.Atkins. Chemistry Molecules, Matter and Change. 4th Edition.
[edit]Appendix 2D gives a value of 2720°C.
31 Ga gallium
[edit]CRC boiling point for gallium
[edit]I can't read this myself right now but someone on a science forum reported to me the value is 2403°C, whereas Jdrewitt reports here that the CRC handbook's later editions list a value of "2204 degrees C (2477 K)". In that same discussion ChrisHodgesUK reports that the 66th and earlier editions give "2403°C".
It would be interesting to learn why the CRC Handbook editors changed this value, what their sources were, but meantime I think Wikipedia is correct to list the value from the most recent editions as the "CRC value" in the table in the page under discussion here.
Peter Dow (talk) 00:12, 12 November 2010 (UTC)
WEL boiling point for gallium
[edit]The "WEL" is quoting the Webelements.com value or 2477 [or 2204 °C (3999 °F)] K faithfully. However, we are told on this page that the webelements.com website takes its values in turn from two sources - (1) James & Lord and (2) Kaye & Laby —Preceding unsigned comment added by Peter Dow (talk • contribs) 19:25, 10 November 2010 (UTC)
James & Lord boiling point for gallium
[edit]Unknown at this time.
Kaye & Laby boiling point for gallium
[edit]Kaye & Laby give two values for the boiling point of gallium which can be read online.
(1) Properties of the elements 3.1.2 - the value is 2200°C
(2) Standard molar heat capacities and properties of melting and evaporation of the elements 3.10.1 - the value for Tvap is 2480K. By my calculation 2480K = (2480 - 273)°C = 2207°C.
LNG boiling point for tin
[edit]Unknown at this time.
Other reference sources for the boiling point of gallium
[edit]D.W.A. Sharp. Dictionary of Chemistry. Penguin. 2nd Edition
[edit]The value is 2403°C.
L.Jones & P.Atkins. Chemistry Molecules, Matter and Change. 4th Edition.
[edit]Appendix 2D gives a value of 2070°C.
Observations on the reference data values
[edit]The values reported from the earlier editions of the CRC Handbook seem to agree with the Penguin Dictionary of Chemistry. Possibly they take their values from the same source.
The values quoted in books and on other websites vary widely yet this variety is not reflected in the choice of values which appear in the wikipedia data page under discussion. From reading the data in the table here one might suppose that all significant references were pretty much in agreement as to the values which were all agreeing within experimental error. The reverse is the case; values vary a lot well outside experimental error and we need an explanation or a debate and discussion at the very least as to which values are correct and why wikipedia stands by the values it has at the moment.
Suggestions as to why measured boiling points vary so much
[edit]I am proposing to list a number of suggestions and I invite discussion on each.
Superheating of the liquid
[edit]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
[edit]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
[edit]Temperature measuring devices may have been wrongly calibrated or misread?
Chemical contamination of the sample
[edit]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?
Estimated not measured boiling points
[edit]The various values quoted may not all be direct measurements of the boiling points but may have been estimated by extrapolating from lower temperature vapour pressures. Similar sources of error as suggested above arise in measuring the lower temperature vapour pressures and in addition further variability could arise from different extrapolation and estimation methods.
Peter Dow (talk) 18:19, 13 November 2010 (UTC)
Silicon
[edit]- http://www.silicon-wafers.com/msds among other reliable sources lists 2355C as the correct value. This is significantly lower than the currently listed number. Anyone have a reliable source for the higher value?