Factitious airs

Factitious airs was a term used for synthetic gases which emerged around 1670 when Robert Boyle coined the term upon isolating what is now understood be hydrogen. "Factitious" means "artificial, not natural", so the term means "man-made gases". The study of these airs interfaced with phlogiston theory. The therapeutic potential of factitious airs were widely investigated with significant contributions by Thomas Beddoes, James Watt, Humphry Davy, and others at the Pneumatic Institution.
Henry Cavendish (1731–1810) used the term "factitious air" to refer to "any kind of air which is contained in other bodies in an unelastic state, and is produced from thence by art", and also defined "fixed air" (carbon dioxide): "By fixed air, I mean that particular species of factitious air, which is separated from alcaline substances by solution in acids or by calcination". Georgiana Cavendish, Duchess of Devonshire (related to Henry through marriage) had a profound interest in chemistry with interest in Henry's research in pneumatic chemistry. She played a pivotal role in advancing the study of factitious airs through partnering with Thomas Beddoes to establish the Pneumatic Institution.
Although there are significant inconsistencies in the archaic nomenclature due to the limited knowledge of chemistry and primitive analytical technology of the era (i.e. based on the chemistry, it is clear the terms were mistakenly assigned to more than one gas by different investigators). Furthermore, in most cases the gases were not pure. Names used for factitious airs may have included:
Tuberculosis was a primary disease physicians had attempted to treat with factitious airs, particularly since James Watt's daughter died of the disease. John Carmichael had reported successfully treating a patient suffering from tuberculosis using hydrocarbonate. This application of factitious air was pioneering research relevant to the modern era as carbon monoxide currently has preclinical evidence of treating "Mycobacterium tuberculosis" infection progression by inducing dormancy, stimulating host immune response, and ameliorating host inflammation.