“I have already stated that I was not able to find again the lost air. One might indeed object that the lost air remains in the residual air which can no more unite with phlogiston; for, since I have found that it is lighter than ordinary air, it might be believed that the phlogiston, united with this air, makes it lighter, as appears to be known already from other experiments. But since phlogiston is a substance, which always presupposes some weight, I much doubt whether such hypothesis has any foundation.”[17] He had formerly conjectured that hydrogen, the “air” obtained by the action of vitriol on zinc, might be phlogiston; “still, other experiments are contrary to this.” Scheele next directs attention to acid of nitre, and points out that when prepared in absence of organic material, it is nearly colourless; but that if phlogiston be given to it, it becomes red. At the end of a distillation of pure nitre with pure sulphuric acid, however, red fumes are produced: “Where does the acid now obtain its phlogiston? There is the difficulty.” He collected some of this “red air” in a bladder containing milk of lime, to prevent its corrosive action; and having tried whether the resulting gas, which was now no longer red, would support combustion, “the candle began to burn with a large flame, whereby it gave out such a bright light that it was sufficient to dazzle the eyes. I mixed one part of this air with three parts of that air in which fire would not burn; I had here an air which was like the ordinary air in every respect. Since this air is necessarily required for the origination of fire, and makes up about the third part of our common air, I shall call it after this, for the sake of shortness, Fire-air; but the other air, which is not in the least serviceable for the fiery phenomena, I shall designate after this with the name already known, Vitiated air.”[18] How history repeats itself! Here is Scheele, in 1772, reproducing Mayow’s name “fire-air particles” for the same substance of which Mayow had inferred the existence a century before, and which he had pointed out as being present in the acid of nitre, as well as in common air.