Air phlogisticated

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. 

Similar to Black, Daniel Rutherford (1749-1819) studied gases for his medical degree dissertation. Rutherford found that common air contained a part that supported respiration and a part that did not. Initially, Rutherford assumed the part that did not support respiration was contaminated by fixed air. Rutherford experimented and removed the fixed air, and he discovered the uncontaminated air still did not support life or combustion. Rutherford assumed the gas he had isolated was ordinary air saturated with phlogiston hence, it was phlogisticated air, which he referred to as noxious air. What Rutherford had isolated was nitrogen, and he is given credit for its discovery. 

Lavoisier then heated the mercury calx formed, collecting the gas produced. It proved to be the eminently respirable air, that is, Priestley s de-phlogisticated air. When this air was recombined with the vitiated or mephitic air,... 

By phlogisticated air Priestley understood any air which had been rendered noxious, that is, a nonsupporter of combustion or respiration, this condition being generally recognized by chemists of the time to be produced by the phlogiston given off when substances were burned or when metals were calcined.30... 

Another important discovery by Cavendish is based upon an observation of Priestley. Priestley had experimented by passing the electric spark through air confined over water colored with litmus, and found that the air was diminished in volume and that the litmus was reddened. As Priestley believed that electricity was another form of phlogiston, his results were puzzling to him. His curiosity excited by Priestley s observations, Cavendish also attacked the problem. This resulted in his proof that, by this means, practically all the phlogisticated air could by a sufficient... 

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. ... 

Between me and the door was my chair, plain oak with curved arms—the chair also used by visitors. That chair, set at an angle to the hearth, spoke of absence. I associated Shales with quiet rooms, with moments of sudden calm. I decided that when he came back, I would visit him in his little study, sit in the chair by his desk, and direct him to collect the airs from his plants so that we could try out Mayow s experiments. I would offer to work with him on the extra chapter of his book. After all, I would soon complete my work on palingenesis and therefore be free to undertake a new project. We would test to see whether those exhaled airs were the same as common air. And then we would collect the air that is left when a candle has been burned under a flask, the so-called phlogisticated air, and discover its qualities. 

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. ... 

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