441. It was formerly estimated that the weight of pure atmospheric air is 305,000 grains troy for one million of cubic inches; but the latest authorities assign it to be 310,117 grains. Of this weight of one million of cubic inches of pure air,
| The weight of the oxygen is | 71,809.3 |
| The weight of the azote is | 238,307.7 |
| ————- | |
| Total | 310,117.0 |
442. But common atmospheric air in its ordinary state contains in 1000 cubic inches,
| Of pure air | 989 |
| Of the vapour of water | 10 |
| Of carbonic acid gas | 1 |
Ten inches of pure air are equal in weight to nine of oxygen.
Eight inches of azote are equal in weight to seven of oxygen.
The specific gravity of carbonic acid is to pure air at the rate of 15,277 to 10,000.
The specific gravity of the vapour of water is to pure air as 6,230 to 10,000. It follows that a million of cubic inches of air in its ordinary state weigh 309,111½ grains.
Carbonic acid gas is composed of oxygen and pure carbon in the proportion of eight grains of oxygen to three of carbon out of every eleven grains of carbonic acid.
443. Though during particular portions in the twenty-four hours, under circumstances which influence variously the actions of life (437 and 438), the quantity of the oxygen consumed, of carbonic acid generated, and of azote absorbed, vary (436 to 439), yet it is probable that the daily consumption, reproduction, and absorption of these gases, is pretty much the same one day with another. The experiments of Dr. Edwards clearly show that while these quantities vary to such an extent, when the observation embraces only a short interval, as to be scarcely ever the same hour by hour, yet that they lessen as the interval extends, until at length a nearly exact equilibrium is established.