Phlogistication of air

Priestley s later views on calcination were based on Cavendish s theory, that the metals gave out phlogiston whilst at the same time the calx absorbed water or fixed air, both produced by the phlogistication of air. Beddoes said it now remained to find if in the calcination of metals a quantity of water, equal to the difference of weight, is generated during calcination . 

The young doctor noticed that life forms and burning phosphorus only used part of air. The remainder he called "phlogisticated air", which we now know as nitrogen. 

Certain experiments [said he] appear to show. . . that it consists of atmospheric air in union with phlogistic material for it is never produced except from bodies which abound in inflammable parts, the phlogiston ever appears to be taken up by other bodies, and is hence of value in reducing the calces of metals. I say from phlogistic material, because as already mentioned, pure phlogiston, in combination with common air, can be seen to yield another kind of air. . . (25). 

Priestley s first chemical paper, Observations on Different Kinds of Air appeared in the Philosophical Transactions of the Royal Society in 1772. The results are described within a phlogistic terminology sufficiently well developed that it is easy to believe that phlogistic thinking guided the formulation of the very experiments he is reporting. 

We may safely conclude, [be says] that in the present experiments the phlogisticated air was enabled by means of the electric spark to unite to form a chemical combination with the dephlogisticated air, and was-thereby reduced to nitrous (that is, our nitric ) acid, which united to the soap-lees and formed a solution of nitre.. .. A fur-thur confirmation of it is, that, as far as I can perceive, no diminution of air is produced when the electric spark is passed either through pure dephlogisticated air, or through perfectly phlogisticated air, which indicates the necessity of a combination between these two airs to produce the acid. ... 

Nitrous oxide was discovered by J. Priestly at the end of the eighteenth century. In 1800, aged 21, H. Davy published a 580-page book entitled Nitrous Oxide, or De-Phlogisticated Nitrous Air, and its Respiration, in which he described his experiments... 

The first experimental evidence for the noble gases was obtained by Henry Cavendish in 1766. In a series of experiments on air, he was able to sequentially remove nitrogen (then known as phlogisticated air ), oxygen ( dephlogisticated air ), and carbon dioxide ( fixed air ) from air by chemical means, but a small residue, no more than one part in 120, resisted all attempts at reaction. The nature of Cavendish s unreactive fraction of air remained a mystery for more than a century. This fraction was, of course, eventually shown to be a mixture of argon and other noble gases. ... 

All these eighteenth century investigators expressed their views on the action of air and combustion in terms of the phlogistic theory of Becher and Stahl, and it remained for Antoine-Laurent Lavoisier, the French savant, who fell a victim to the guillotine in 1794, to free them from this incubus and to develop the new theory wherein oxygen was assigned its proper role as a constituent of air and a supporter of combustion. 

And, nevertheless, the phlogistic theory was recognized for about a century and was earnestly advocated by famous chemists of that time including G. Cavendish, J. Priestley, and C. Scheele whose names are associated with the discovery of the elements of air and water. At the initial stages of their discoveries the concepts of the phlogistic theory played an important role. 

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