Excerpt from the lecture notes of Professor Samuel Williams, Hollis Professor of Mathematics and Natural Philosophy at Harvard University, USA, 1780 - 1788.
Note: Oxygen was dicsovered in Europe in 1774. Lavoisier's Traité élŽémentaire de chimie ("Elementary Treatise of Chemistry") was published in 1789.
"Among the various kinds of permanently elastic Fluids we may begin with the Common or Atmospherical Air. Atmospherical Air is that which we breathe, with which we are constantly surrounded, and which is common to every country and place. And with regard to this kind of Air several observations may be made. Thus: Common or atmospherical Air may combine, or be charged with many substances. - Thus water is held in solution by Air, and Rain, Snow, and Hail appear to be precipitations from it. ... But what is worthy of particular observation, common or atmospherical Air is generally charged with a large quantity of Fire or Phlogiston. The Chemists speak of Fire and Phlogiston as being the same thing, or signifying the same element. But we are not absolutely certain that this is the case. By Phlogiston we mean no more than the principle of Inflammability; or that by which bodies become combustible or capable of burning. - And that there is such a principle or element as Phlogiston, and that the common Air may be charged with large quantities of it may be easily represented.
"Example: Take some combustible substance and let it be inflamed or set on fire: In this state enclose it in a vessel containing a small quantity of atmospherical air. Effect. The combustion will continue but a small time and then cease. Part of the combustible substance is reduced to ashes and the other part remains entire. And the Air appears to be changed and altered. ... Here then we have a representation of what chemists call Phlogiston and of the Air's being loaded with it. In the confined air the combustible matter continues burning until the air becomes loaded with something that prevents any further combustion. And being confined by the closeness of the vessel whatever the matter be with which the air is loaded it is confined within the vessel and cannot escape. ...
"It seems therefore from this Experiment that Phlogiston must be a real Substance, and that the Air is loaded or saturated with it. For what can the enclosing the combustible matter in the Phial do but to prevent the escape or dispersion of some real substance? And is it not evident that so long as the air can receive this substance from the combustible matter so long the body will continue burning; and that as soon as the Air is saturated and can receive no more Phlogiston, the combustion must cease for no more Phlogiston can escape or be thrown out from the burning body. And therefore when fresh air is admitted to receive Phlogiston, the combustion will again take place. - And hence are derived the phrases of phlogisticated and dephlogisticated air. By phlogisticated air is intended air which is charged or loaded with Phlogiston, and by dephlogisticated air is meant Air which is free from Phlogiston; or which does not contain this principle or element of inflammability."
Conant, J. B. (1964) The Overthrow of the Phlogiston Theory: The Chemical Revolution of 1775 - 1789. In: Conant, J. B.and L. K. Nash (eds.) Harvard Case Histories in Experimental Science, Harvard University Press, Cambridge, Massachusetts, vol. I, 65 - 115.