1. In his early experiments Lavoisier thought that the gas liberated on heating powdered charcoal in a bell jar kept over water in a trough was like fixed air i.e., carbon dioxide.
2. The next series of experiments deals with the combustion of phosphorous in a bell jar. From this he showed that whatever it was in the atmospheric air which combined with the phosphorous was not water vapour.
3. This was respirable air, a component of air that also helped in burning.
4. The air that we breathe out precipitated lime water while that after heating metal did not.
5. From this, he concluded that there were two processes involved in respiration.
6. Lavoisier carried out another experiment by which he showed that about one sixth of the volume of ‘vitiated air’ consists of chalky acid gas (fixed air).
7. Either eminently respirable air is changed in the lungs to chalky acid air; or an exchange takes place, the eminently respirable air being absorbed, and an almost equal volume of chalky acid air being given up to the air from the lungs.
8. Lavoisier had to admit that there were strong grounds for believing that eminently respirable air did combine with the blood to produce the red colour
