Fourth Report of the Committee on Atomic Weights of the International Union of Chemistry

Abstract

The results of Cooper and Maass on the density of carbon dioxide (Second International Report) and of Moles and Salazar (Third International Report) on carbon monoxide give slightly lower values, 12.0054 and 12.006, respectively. Until further confirmation of a higher value has been obtained, it seems inadvisable to make a change in the value in the table of atomic weights.Nitrogen.-Moles and Batuecas4 correct their results for the density of ammonia previously published (see Report for 1931). The corrected densities are

Heats-of-combustion and of formation of the normal paraffin hydrocarbons in the gaseous state, and the energies of their atomic linkages

“…For n > 5 AHVi = -(7.913 ± 0.010) -n(5.55 ± 0.13) k-cal 15 per mole. (13) With diamond as the standard state for carbon the analogous equations are: 7iC (diamond) + (7i+l)H 2 (gas) = C n H 2n+2 (gas), (14) AHVi = Qcm.i -71(162.77 ±0.10)-(68.313 ± 0.010) k-cali 5 per mole; (15) and for ti>5, The values computed from these equations are given in table 2. 7iC(/3-graphite)+(n+l)H2 (gas) = C"H2"+2 (gas) «C (diamond) 4-(7i-f-l)H2 (gas) = C"H2"+2 (gas) Note.-The estimated uncertainties given here represent the absolute error in each of the values.…”

Heat and free energy of formation of carbon dioxide, and of the transition between graphite and diamond

“…I Roth and his coworkers determined tbeamount olreaction Irom the mass 01 sample placed in the crucible in the bomb less tbe mass of solid material remaining in tbe bomb after the combustion. In 1934, tbeatomic weigbt of carbon was given in tbe international table as 12.00 (18].…”

“…Combining these three values for H 0298 . 16-Hoo with eq 6 and 7, there is obtained for the heat of reaction at the absolute zero of temperature for C (c, graphite) +02 (g)=C02 (g) (1) t:..HO 0= -393,018 ±48 NBS into j/mole, or -93,949 ± 11 cal/mole (18) From a plot of the data on the heat capacity of diamond by Pitzer [48] from 70° to 300° Ie, with an appropriate extrapolation to 0° Ie, the present writers obtain for C (c, diamond), H0298.16-Hoo=536.3 ±2.5 into j/mole, or 128.2 ±0.6 cal/mole. Combining this value and those given above for oxygen and carbon dioxide with eq 15, there is obtained for the heat of reaction at the absolute zero of temperature for …”

Heats of combustion and of formation of the normal aliphatic alcohols in the gaseous and liquid states, and the energies of their atomic linkages

“…These values are given in table 3 and are plotted in figure 3. C B H 2n+2 (gas) + %02 (gas) = C n H 2n+1 OH (gas)…”