+---------------+-------------+------------+------------+ | |Concentration| Molecular | Mean | | Gas. | cc. per grm.|Latent Heat.|Temperature.| | | | | Absolute. | +---------------+-------------+------------+------------+ | Helium | 97 | 483.0 | 18° | | Hydrogen | 390 | 524.4 | 18° | | Hydrogen | 20 | 2005.6 | 78° | | Nitrogen | 250 | 3059.0 | 82° | | Oxygen | 300 | 3146.4 | 82° | | Carbon dioxide| 90 | 6099.6 | 180° | +---------------+-------------+------------+------------+ _Heat of Occlusion._--In every case when gases are condensed to the liquid state there is evolution of heat, and during the absorption of a gas in charcoal or any other occluding body, as hydrogen in palladium, the amount of heat evolved exceeds that of direct liquefaction. From the relation between occlusion-pressure and temperature at the same concentration, the reaction being reversible, it is possible to calculate this heat evolution. Table VIII. gives the mean molecular latent heats of occlusion resulting from Dewar's experiments for a number of gases, having concentrations in the charcoal as shown. The concentrations were so regulated as to start with an initial pressure not exceeding 3 mm. at the respective boiling-points of hydrogen, nitrogen, oxygen and carbon dioxide.