b. In the following experiments on the respiration of atmospheric air in the mercurial airholder; the composition of the gas before inspiration and after expiration, was ascertained in the following manner.
Forty measures of it were agitated over mercury in solution of caustic potash, and suffered to remain in contact with it for two or three hours. The diminution was noted, and the gas absorbed judged to be carbonic acid. Twenty measures of the gas, freed from carbonic acid, were mingled with thirty of nitrous gas, in a tube of,5 inches diameter; they were not agitated,[200] but suffered to rest for an hour or an hour and half, when the volume occupied by them was noticed: and 50-m the volume occupied, divided by 3 considered as the oxygene x, and 20-x considered as the nitrogene.
c. To ascertain the changes effected in atmospheric air by single inspirations,
I made, after a compleat voluntary exhaustion of my lungs, at temperature 61°, one inspiration and expiration of 141 cubic inches of atmospheric air. After expiration, they filled a space equal to 139 cubic inches nearly. These 139 cubic inches analised were found to consist of
| Nitrogene | 101 |
| Oxygene | 32 |
| Carbonic acid | 6 |
The 141 cubic inches before inspiration, were composed of 103 nitrogene, 1 carbonic acid and 37 oxygene. The time taken to perform the inspiration and full expiration, was nearly a quarter of a minute.
I repeated this experiment seven or eight times, and the quantity of oxygene absorbed was generally from 5 to 6 cubic inches, the carbonic acid formed from 5 to 5,5, and the quantity of nitrogene apparently diminished by from 1 to 3 cubic inches.
E. 2. I made, after a voluntary expiration of common air, one inspiration and full expiration of 100 cubic inches of atmospheric air. It was diminished nearly to 98¾ or 99 cubic inches, and analised, was found to consist of
| Nitrogene | 71,7 |
| Oxygene | 22,5 |
| Carbonic acid | 4,5 |
This experiment I likewise repeated four or five times, with very little difference of result, and there always seemed to be a small diminution of nitrogene. I made no corrections on account of the residual air of the lungs in these processes, because there was every reason to suppose that it was always of similar composition.