Reference Label | Details |
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Jessup 1938 | R. S. Jessup, J. Res. Natl. Bur. Stand. 21, 475-490 (1938) Heats of Combustion of Diamond and of Graphite |

Rossini 1938 | F. D. Rossini and R. S. Jessup, J. Res. Natl. Bur. Stand. 21, 491-513 (1938) Heat and Free Energy of Formation of Carbon Dioxide, and of the Transition between Graphite and Diamond |

note CO2a | Jessup 1938 reports the heats of combustion, -DeltaU, in int. kJ/mol, for solid carbon to form 1 mole of CO2 (44.010 g) at 30° C and pressure of 1 atm, as follows: Ceylon nat. graphite #1 393.402 +- 0.019; Ceylon nat. graphite #2 393.394 +- 0.026; Ceylon nat. graphite 3#3 393.324 +- 0.032; Buckingham nat. graphite 393.310 +- 0.016; Artificial Graphite #1 393.449 +- 0.020;Artificial Graphite # 2 393.438 +- 0.025. Further correction for heat capacities at constant volume is 1.5 J/mol/K, for a total of 7.5 J/mol to transform the results to 298.15 K. Jessup 1938 takes the correction for external work (p DeltaV) as -11 J/mol. This was later recalculated by Hawtin 1966 to be -12 J/mol. Also, Prosen 1944a find that the data of Jessup 1938 have to be increased by 0.0071% in order to compensate for slight errors. Finally, the result has to be corrected for the changed molecular weight of CO2. Hawtin 1966 make the corrections, but apparently do not take into account all that is needed. They use the equation -DeltaHstd298(correct,cal/mol) = 0.2390681[-DeltaH298(int.J/mol)-32]. Their factor 0.2390681 = 44.011/44.010*1.000071/4.1833. The reduction by 32 int. J/mol is the sum of (-33 +1). However,it is not quite clear how they get -DeltaH298 from -DeltaU303. Other than increasing the -DeltaU values by 11 int. J/mol, it seems that no correction for difference in temperature has been taken, or it amounts to decreasing the values by 1 int. J/mol. (There is also a typo involving the Ceylon nat. graphite #1, which makes the reconstruction of what has been done there difficult.) The temperature correction (-7.5 int. J/mol) used by Jessup 1938 may be too high. He usess Cv of 8.78, 20.82, and 28.08 J/mol for graphite, O2, and CO2. This gives -1.52 int. J/mol/K, or for 5 K -7.6 int. J/mol. using more current values for Cp reduced by R for the two gases to get Cv: 303.15 K, 8.699, 21.089, 29.049, for a difference of -0.739 J/mol/K or -3.7 J/mol for 5 K; at 298.15 K 8.528, 21.064, 28.821, for a difference of -0.771 J/mol/K or -3.8 J/mol for 5 K; using the average temperature gives -3.8 J/mol for 5 K. (Note that using Cv or Cp in this case leads to the same result, since the amount of gas is the same on both sides of the equation.) Indeed, the enthalpy increment [H303.15-H298.15] for the reaction C |

note CO2c | Rossini 1938 re-evaluates the data of Jessup 1938 and Dewey 1938 and arrives at the weighted average enthalpy of combustion of graphite at 298.15 K to form 44.010 g of CO2 of -393355 +- 46 int. J/mol. Rossini 1940 restates the exact same result. This corresponds to -393418 +- 46 abs. J/mol, or for 44.0095 g of CO2 to 393.413 +- 46 abs. kJ/mol. This is slightly lower than our reinterpretation, see note CO2 and note CO2a, which produces a weighted average of 393.473 kJ/mol. Rossini also similarly analyses the combustion of diamond, arriving at -395254 - 115 int. J/mol. From these he derives the enthalpy for C |