His chief books on chemistry were six volumes of Experiments and Observations on different Kinds of Air, published between 1774 and 1786; Experiments on the Generation of Air from Water (1793) Experiments and Observations relating to the Analysis of Atmospheric Air, and Considerations on the Doctrine of Phlogiston established and that of the Composition of Water refuted (1800).
Was primarily based upon certain experiments on combustion and calcination, and in effect reduced the number of the alchemical principles, while setting up a new one, a principle of combustibility, named phlogiston (from (PXoyun-6s, burnt).
The inflammable principle phlogiston, and another element- " water," " acid " or " earth."
The violence or completeness of combustion was proportional to the amount of phlogiston present.
Be recovered by adding phlogiston, and experiment showed that this could generally be effected by the action of coal or carbon, which was therefore regarded as practically pure phlogiston; the other constituent being regarded as an acid.
The objections of the antiphlogistonists, such as the fact that calces weigh more than the original metals instead of less as the theory suggests, were answered by postulating that phlogiston was a principle of levity, or even completely ignored as an accident, the change of qualities being regarded as the only matter of importance.
Yet really the transition from the one theory to the other was simple, it being only necessary to change the " addition or loss of phlogiston " into the " loss or addition of oxygen."
Stahl was the author of the theory of" phlogiston "in chemistry, which in its day had great importance.
As the prevalence of the conceptions signified and inspired by the word "phlogiston" kept alive ontological notions of disease, so the dissipation of vitalistic conceptions in the field of physics prepared men's minds in pathology for the new views opened by the discoveries of Pasteur on the side of pathogeny, and of J.
The causticity of alkaline bodies was explained at that time as depending on the presence in them of the principle of fire, "phlogiston"; quicklime, for instance, was chalk which had taken up phlogiston, and when mild alkalis such as sodium or potassium carbonate were causticized by its aid, the phlogiston was supposed to pass from it to them.
This theory regarded combustibility as due to a principle named phlogiston (from the Gr.
On this theory, all substances which could be burnt were composed of phlogiston and some other substance, and the operation of burning was simply equivalent to the liberation of the phlogiston.
In his memoir of 1785 he writes: "As far as the experiments hitherto published extend, we scarcely know more of the phlogisticated part of our atmosphere than that it is not diminished by lime-water, caustic alkalies, or nitrous air; that it is unfit to support fire or maintain life in animals; and that its specific gravity is not much less than that of common air; so that, though the nitrous acid, by being united to phlogiston, is converted into air possessed of these properties, and consequently, though it was reasonable to suppose, that part at least of the phlogisticated air of the atmosphere consists of this acid united to phlogiston, yet it may fairly be doubted whether the whole is of this kind, or whether there are not in reality many different substances confounded together by us under the name of phlogisticated air.
Cavendish called it "inflammable air," and for some time it was confused with other inflammable gases, all of which were supposed to contain the same inflammable principle, "phlogiston," in combination with varying amounts of other substances.
Brandt showed that white arsenic was the calx of this element, and after the downfall of the phlogiston theory the views concerning the composition of white arsenic were identical with those which are now held, namely that it is an oxide of the element.
It may be noted here that, while Cavendish adhered to the phlogistic doctrine, he did not hold it with anything like the tenacity that characterized Priestley; thus, in his 1784 paper on "Experiments on Air," he remarks that not only the experiments he is describing, but also "most other phenomena of nature seem explicable as well, or nearly as well," upon the Lavoisierian view as upon the commonly believed principle of phlogiston, and he goes on to give an explanation in terms of the antiphlogistic hypothesis.
Hydrogen they held to be the phlogiston of metals, and they supported this view by pointing out that it was liberated when metals were dissolved in acids.
Indeed, though the partisans of phlogiston did not surrender without a struggle, the history of science scarcely presents a second instance of a change so fundamental accomplished with such ease.