Volume 86 Issue 3 | p. 6 | Letters
Issue Date: January 21, 2008

Boiling Gallium

Department: Letters

Fred Zoepfl's letter to the editor (C&EN, Nov. 12, 2007, page 10), pointed out that the boiling point of gallium is stated incorrectly in an earlier C&EN article (Sept. 24, 2007, page 107) about the talk on "Inorganic 'Jeopardy'" that I gave at the ACS national meeting in Boston. Zoepfl notes that his CRC Handbook (86th Ed.) gives a value of 2,204 °C for the boiling point of gallium. I own the 64th edition of the CRC and upon checking it I found a gallium boiling point value of 2,403 °C (page B-93). So, did the boiling point of gallium drop by 199 °C in the years between the 64th edition (dated 1983-84) and the 86th edition? I also own the 44th edition of the CRC (published in 1962), which lists a boiling point of 1,983 °C for gallium.

The textbook my students use to prepare for their weekly "Jeopardy" quizzes, D. A. McQuarrie and P. A. Rock, "Descriptive Chemistry," (W. H. Freeman, 1985), shows a gallium boiling point of 2,250 °C. That is the value I expect my students to be familiar with and that I accept as the correct answer on my "Jeopardy" quizzes.

I am not in the habit of double-checking every physical constant listed in every textbook for the courses I teach, and I certainly don't go into the lab to verify published values by measuring them myself. If I did either of those things, I fear I would get nothing else done and would have left the profession years ago. Nevertheless, inspired by Zoepfl's letter to the editor, I checked three other sources that are generally regarded as authoritative. F. A. Cotton et al., "Advanced Inorganic Chemistry," 6th edition (John Wiley & Sons, 1999), lists the boiling point as "~2,250 °C". This is the same value as that found in McQuarrie & Rock, which omits the "~". N. N. Greenwood and A. Earnshaw, "Chemistry of the Elements" (Pergamon Press, 1984), lists a gallium boiling point of 2,403 °C. The National Institute of Standards & Technology database (webbook.nist.gov) lists a gallium boiling point of 2,676 K, or 2,403 °C, in agreement with both the 64th edition CRC and Greenwood & Earnshaw.

I agree with Zoepfl's assertion that cerium has a wider liquid range than gallium. However, the students' textbook for the "Jeopardy" quizzes does not cover the lanthanides or actinides, so I do not think it would be fair to expect them to know anything about the chemical or physical properties of cerium.

J. Van Houten
Colchester, Vt.

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Bernard J Sandman (September 25, 2015 12:26 AM)
The boiling point of gallium is 2229 C (2502 K) per the 96th CRC Handbook Edition. This was measured with pressure tube heat pipes ranging from a vapor pressure of 0.1 bar to 3.0 bar from the reference given in the CRC Handbook. This method is much more accurate than extrapolating from vapor pressure measurements obtain at much lower temperatures. This value is probably within several degrees of the true value. 1983 C is way too low. 2204 C is too low in the 86th CRC Edition. 2250 C is too high and 2403 C is much too high. I have also seen 2209 C, 2225 C & 2237 C in the literature; but do not remember the references. I recommend 2227 C (2500 K) plus or minus 10 K as the true boiling point of gallium using the average of 2225 C & 2229 C as the selected value, since the heat pipe method is the most accurate in determining vapor pressures at elevated pressures. The values of 1983 C and 2403 C should be readily rejected, the values of 2204 and 2209 C appear to be on the low side and 2237 C and 2250 C appear to be on the high side. The average of 2204, 2209, 2225, 2229, 2237 & 2250 is 2226 C. The 96th CRC Handbook occasionally updates the information on the Melting, Boiling, Triple and Critical Temperature of the Elements, therefore the 2229 C value takes presence over all previous values in earlier editions of the CRC Handbooks.

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