There are reviewed the existing data on the entropies of oxygen, carbon dioxide, graphite, and diamond, and those on the heats of combustion of natural and artificial graphite and of diamond, includin §" the results recently obtained in a joint investigation by the National Bureau of tandards and the Coal Research Laboratory of the Carnegie Institute of Technology. The new thermochemical data are combined with values of the entropies to obtain values for the heat and free energy of formation of carbon dioxide, and for the transition between graphite and diamond.For C (c, graphite) +02 (g) =C02 (g), at 25° C, per mole, .1Ho 355 ±46 NBS international joules,030 ± 1l calories,228
This paper gives t he results of bomb calorimetric measurem ents of heats o f co mbu stion at 30° C of o ne sample of cellul ose and four samples of nitrocellulose fr om cotto n linters, and of one sample of cel lulose and four sampl es of nitrocellul ose from wo od pulp. Th e res ults have been combined with values for the heats of formation of carb on d ioxide a nd wate r to obtain values of heats of formation of t he celluloses a nd nitr oc e lllllo~es . Emp ir ical equations are given ex pressin g heat of combustion and h eat of formation of the nitrocel luloses as fun ctio ns of nitrogen conte nt.
The measurements were made by means of a bomb calorimeter, which was calibrated electrically for some of the measurements, and by burning standard sample benzoic acid for the remainder. The samples of liquid were inclosed in thin-walled glass bulbs which were flattened on opposite sides, and were ignited by an electric fuse of iron wire. No combustible material other than the iron wire was required to ignite the liquids. Combustible impurities and carbon dioxide were removed from the oxygen before admitting it to the bomb. Measurements of carbon dioxide and carbon monoxide formed in the combustion indicated that the liquids contained very little inert impurity, and that combustion was very nearly complete. The Washburn correction was applied to the results of the calorimetric measurements. The empirical equation-tlFi250 c= 259.28 + 648.84n+ 0.2587n2, where-tlFi250C is the heat of combustion in international kilojoules per mole of liquid normal Cn Fi2n+2 in gaseous oxygen at 25° C and under a constant pressure of 1 atmospher e, the products of combustion being gaseous carbon dioxide and liquid water, also at 25° C, reproduces the mean values within 0.02 percent.
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