Bibliography #618,909

Reference Label	Details
Hawtin 1966	P. Hawtin, J. B. Lewis, N. Moul, and R. H. Phillips, Phil. Trans. Roy. Soc. (London) A 261, 67-95 (1966) The Heats of Combustion of Graphite, Diamond and Some Non-Graphitic Carbons
note CO2e	Hawtin 1966 perform their own measurements of the enthalpy of combustion of graphite and also analyze all literature data. From this they derive the 298 K "best" value of 94042.8 +- 5.8 cal/mol = 393475.1 +- 24.3 J/mol as a weighted average of all groups of measurements except Prosen 1944 (which they find "significantly" higher than the others), and, for comparison, a value of 94039.7 +- 9.8 cal/mol = 393462.1 +- 41.0 J/mol as a weighted average for spectroscopically pure graphite. The weighted average of their own measurements (in cal/mol, Ticonderoga 94028 +- 17.5; AGKSP 94039 +- 11.9; PGA 94053.4 +- 13.1) is 94042.0 +- 28.9 cal/mol = 393471.6 +- 121.1 J/mol. Note that this uncertainty is 4.3 times std. dev. Taking into account the number of actual samples, a value of 2 times std. dev., 13.4 cal/mol = 56.3 J/mol could be derived. They also obtain for the combustion of diamond the enthalpy at 298 K of 94477.4 +- 29.5 cal/mol = 395293.4 +- 123.4 J/mol. Their "best" for diamond, 94490.1 +- 16.7 cal/mol = 395346.6 +- 69.9 J/mol, takes into account previous data by Jessup 1938. From their "best" values they obtain also for C -> C an enthalpy at 298.15 K of 447.3 +- 17.6 cal/mol = 1871.5 +- 73.6 J/mol. They have determined the amount from weighing the sample and taking the atomic weight of C as 12.011. Therefore, their results can be adjusted to the current atomic weight of 12.01070 as follows: the weighted average of their measurements becomes 393461.8 +- 121.1 (+- 56.3) J/mol; their result for diamond becomes 395283.6 +- 123.4 J/mol. Their "best" value is an average of results where amounts were in some cases determined from the mass of the sample and in some from the mass of the CO2. Normalizing to carbon only, the overall best becomes 393465.2 +-24.3 J/mol, the spectroscopic graphite only becomes 393452.3 +- 41.0 J/mol, and the best diamond becomes 395336.7 +- 69.8 J/mol. The enthalpy of C -> C stays 1871.5 +- 73.6 J/mol. If normalized to CO2 by 44.0095/44.011, these would be 393461.7, 393448.7, 395333.1, and 1871.4 J/mol. For their recommended "best" value, here we adopt the average of the two normalizations, 393463.5 +- 24.3 J/mol for graphite, 395334.9 +- 69.9 J/mol for diamond, and 1871.4 +- 73.6 J/mol for the transition from graphite to diamond. Note that CODATA Key Vals quotes their result for graphite as 393.47 +- 0.06 kJ/mol and Cox 1970 give 94040 +- 12 cal/mol = 393463 +- 50 J/mol. Also, Cox 1970 give for their diamond result 94477 +- 30 cal/mol = 395292 +- 126 J/mol.

Reference Label

Details

Hawtin 1966

P. Hawtin, J. B. Lewis, N. Moul, and R. H. Phillips, Phil. Trans. Roy. Soc. (London) A 261, 67-95 (1966)
The Heats of Combustion of Graphite, Diamond and Some Non-Graphitic Carbons

note CO2e

Hawtin 1966 perform their own measurements of the enthalpy of combustion of graphite and also analyze all literature data. From this they derive the 298 K "best" value of 94042.8 +- 5.8 cal/mol = 393475.1 +- 24.3 J/mol as a weighted average of all groups of measurements except Prosen 1944 (which they find "significantly" higher than the others), and, for comparison, a value of 94039.7 +- 9.8 cal/mol = 393462.1 +- 41.0 J/mol as a weighted average for spectroscopically pure graphite. The weighted average of their own measurements (in cal/mol, Ticonderoga 94028 +- 17.5; AGKSP 94039 +- 11.9; PGA 94053.4 +- 13.1) is 94042.0 +- 28.9 cal/mol = 393471.6 +- 121.1 J/mol. Note that this uncertainty is 4.3 times std. dev. Taking into account the number of actual samples, a value of 2 times std. dev., 13.4 cal/mol = 56.3 J/mol could be derived. They also obtain for the combustion of diamond the enthalpy at 298 K of 94477.4 +- 29.5 cal/mol = 395293.4 +- 123.4 J/mol. Their "best" for diamond, 94490.1 +- 16.7 cal/mol = 395346.6 +- 69.9 J/mol, takes into account previous data by Jessup 1938. From their "best" values they obtain also for C -> C an enthalpy at 298.15 K of 447.3 +- 17.6 cal/mol = 1871.5 +- 73.6 J/mol. They have determined the amount from weighing the sample and taking the atomic weight of C as 12.011. Therefore, their results can be adjusted to the current atomic weight of 12.01070 as follows: the weighted average of their measurements becomes 393461.8 +- 121.1 (+- 56.3) J/mol; their result for diamond becomes 395283.6 +- 123.4 J/mol. Their "best" value is an average of results where amounts were in some cases determined from the mass of the sample and in some from the mass of the CO2. Normalizing to carbon only, the overall best becomes 393465.2 +-24.3 J/mol, the spectroscopic graphite only becomes 393452.3 +- 41.0 J/mol, and the best diamond becomes 395336.7 +- 69.8 J/mol. The enthalpy of C -> C stays 1871.5 +- 73.6 J/mol. If normalized to CO2 by 44.0095/44.011, these would be 393461.7, 393448.7, 395333.1, and 1871.4 J/mol. For their recommended "best" value, here we adopt the average of the two normalizations, 393463.5 +- 24.3 J/mol for graphite, 395334.9 +- 69.9 J/mol for diamond, and 1871.4 +- 73.6 J/mol for the transition from graphite to diamond. Note that CODATA Key Vals quotes their result for graphite as 393.47 +- 0.06 kJ/mol and Cox 1970 give 94040 +- 12 cal/mol = 393463 +- 50 J/mol. Also, Cox 1970 give for their diamond result 94477 +- 30 cal/mol = 395292 +- 126 J/mol.