Keeping in view these general considerations, it is now proposed to estimate, under ordinary terrestrial atmospheric conditions, the total energy properties of the three gaseous substances, oxygen, nitrogen, and aqueous vapour. The information relative to the energy calculation which is in the meantime available is shown below in tabular form. As far as possible all the heat and other energy properties of each substance as it cools to absolute zero have been taken into account. _Table of Properties_ +--------+---------+----------+----------+-------------+-------+---------+ | I | II | III | IV | V | VI | VII | +--------+---------+----------+----------+-------------+-------+---------+ | |Specific | Evaporation | | | | | | Heat at |Temperature of Liquid| Approximate | Latent| Vapour | | Gas | Constant| at Atmospheric | Latent Heat |Heat of|Pressure.| | |Pressure.| Pressure. |of Gas 50° F.|Liquid.| 50° F. | | | | °F. °F. (Abs.)| | | | +--------+---------+----------+----------+-------------+-------+---------+ |Oxygen | 0·2175 | -296 | 164 | 100 | ... | ... | +--------+---------+----------+----------+-------------+-------+---------+ |Nitrogen| 0·2438 | -320 | 141 | 100 | ... | ... | +--------+---------+----------+----------+-------------+-------+---------+ |Aqueous | | | | | | | |Vapour | 0·4 | 212 | 673 | 1080 | 144 | 0·176 | +--------+---------+----------+----------+-------------+-------+---------+ Since no reliable data can be obtained with regard to the values and variations of specific heats at extremely low temperatures, they are assumed for the purpose of our calculation to be in each case that of the gas, and to be constant under all conditions. Latent heats are utilised in every case when available. With these reservations, the total energy, referred to absolute zero, of one pound of oxygen gas at normal temperature of 50° F. or 511° F. (Abs.) will be approximately (511 × 0·2175) + 100 = 211 Thermal Units Fahrenheit. This in work units is roughly equivalent to 211 × 778 = 164,000 ft. lbs. Adopting the same method with nitrogen gas, its energy at the same initial temperature will be, per unit mass, 174,600 ft. lbs. There is thus a somewhat close resemblance, not only in the general temperature conditions but also in the energy conditions, of the two gases oxygen and nitrogen. It will be readily seen, however, that under the same conditions the energy state of aqueous vapour differs very considerably from either, for by the same method as before the energy per pound of aqueous vapour is equal to {(511 × 0·4) + 1080 + 144} × 778 = 1,111,000 ft. lbs.