I observed before that this acid vapour, or air, has a strong affinity with _phlogiston_, so that it decomposes many substances which contain it, and with them forms a permanently inflammable air, no more liable to be imbibed by water than inflammable air procured by any other process, being in fact the very same thing; and that, in some cases, it even dislodges spirit of nitre and oil of vitriol, which in general appear to be stronger acids than itself. I have since observed that, by giving it more time, it will extract phlogiston from substances from which I at first concluded that it was not able to do it, as from dry wood, crusts of bread not burnt, dry flesh, and what is more extraordinary from flints. As there was something peculiar to itself in the process or result of each of these experiments, it may not be improper to mention them distinctly. Pieces of dry _cork wood_ being put to the acid air, a small quantity remained not imbibed by water, and was inflammable. Very dry pieces of _oak_, being exposed to this air a day and a night, after imbibing a considerable quantity of it, produced air which was inflammable indeed, but in the slightest degree imaginable. It seemed to be very nearly in the state of common air. A piece of _ivory_ imbibed the acid vapour very slowly. In a day and a night, however, about half an ounce measure of permanent air was produced, and it was pretty strongly inflammable. The ivory was not discoloured, but was rendered superficially soft, and clammy, tasting very acid. Pieces of _beef_, roasted, and made quite dry, but not burnt, absorbed the acid vapour slowly; and when it had continued in this situation all night, from five ounce measures of the air, half a measure was permanent, and pretty strongly inflammable. This experiment succeeded a second time exactly in the same manner; but when I used pieces of white dry _chicken-flesh_ though I allowed the same time, and in other respects the process seemed to go on in the same manner, I could not perceive that any part of the remaining air was inflammable. Some pieces of a whitish kind of _flint_, being put into a quantity of acid air, imbibed but a very little of it in a day and a night; but of 2-1/2 ounce measures of it, about half a measure remained unabsorbed by water, and this was strongly inflammable, taking fire just like an equal mixture of inflammable and common air. At another time, however, I could not procure any inflammable air by this means, but to what circumstance these different results were owing I cannot tell. That inflammable air is produced from _charcoal_ in acid air I observed before. I have since found that it may likewise be procured from _pit coal_, without being charred.