Gas or Simply Semi-phlogisticated Nitrous Air

Some of the confusions engendered by the phlogiston theory can be briefly illustrated by the nomenclature described above. For example, factitious airs referred to gases derived from solids. Heating chalk (calcium carbonate, 

This is an early nineteenth-century engraving depicting Priestley s pneumatic apparatus. The collection of carbon dioxide from the gun barrel over a dish of mercury is to be found in J. Priestley, Experiments and Observations on Different Kinds of Air, and Other Branches of Natural Philosophy, Vol. Ill, Thomas Pearson, Birmingham, 1790, Plate 11, as well as earlier editions. 

Hofimann and V. Torrence, Chemistry Imagined—Reflections on Science, Smithsonian Institution Press, Washington, EX2, 1993, pp. 82—85. 

FIGURE 198. Collage of Joseph Priestley s pneumatic apparatus. A gun barrel is used as reaction chamtx and placed in a fireplace. The resulting gases, if water-soluble, are collected over mercury (Fig. 11). 

We know also that nitrogen dioxide dissolves in water to form nitric acid  

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