Light phlogiston

Although Lavoisier completely renounced phlogiston as a material substance, he nevertheless retained in his list of chemical elements two unweighable, immaterial ones—light and "caloric —which in the opinion of Boris N. Menschutidn "presented an unmistakable likeness to the principle phlogiston, as conceived by Stahl (78). 

Lavoisier summarized his ideas developed over the previous twenty years in his seminal 1789 book Traite Elementaire de Chimie (Elements of Chemistry). This work presented his findings on gases and the role of heat in chemical reactions. He explained his oxygen theory and how this theory was superior to phlogiston theory. Lavoisier established the concept of a chemical element as a substance that could not be broken down by chemical means or made from other chemicals. Lavoisier also presented a table of thirty-three elements. The thirty-three elements mistakenly included light and caloric (heat). Lavoisier put forth the modern concept of a chemical reaction, the importance of quantitative measurement, and the principle of conservation of mass. The final part of Lavoisier s book presented chemical methods, a sort of cookbook for performing experiments. 

The matter of the Sun, or of Light, the Phlogiston, Fire, the Sulphureous Principle, the Inflammable matter, are all of them names by which the Element of Fire is usually denoted. But he adds that we need to distinguish between its free and combined states. In the free state, fire is the essential fluid, it makes all other bodies fluid if present in sufficient quantity. Air itself might become solid, if it could be entirely deprived of the Fire it contains. This view is also to be found in the lectures of his teacher, Rouelle. 

Phlogiston or fixed fire differs from free fire in that it communicates neither heat nor light to the compounds in which it is combined. Nor does it produce a change in its state. We can convey it from the body with which it is joined into another body, so that it shall enter into its composition thereof, and remain fixed in it. When this happens, both bodies show considerable change this is what requires its distinction from free fire and to consider it as the element of Fire combined with some other substance It is ironic that Macquer s clear distinction of chem-... 

In the old Phlogiston Theory, phlogiston is equivalent to minus oxygen in the later theory it was sometimes assumed to be hydrogen (Cavendish, Kirwan, Priestley), or the matter of light (Macquer). Practically every chemist adopted the theory during the eighteenth century. 

One must not confound elementary Fire with the fire of the cook-stove, and one must observe that the former becomes an actual burning fire only when combined with combustible substance of itself it gives neither flame, nor Light. Thus the Phlogiston, or a substance oily, sulphurous, resinous, is not the principle, but simply the matter suitable to maintain and manifest it.39... 

He provided an explanation of the heat and light produced in combustion as an alternative to the phlogiston theory. 

Priestley, accepting these results, discussed them with the members of the Lunar Society and the Lunatics, as they were called, agreed with him. Boulton especially was enthusiastic. We have long talked of phlogiston, he declared, without knowing what we talked about, but now that Dr. Priestley brought the matter to light we can pour that element... 

In every case, wherein dephlogisticated air has been produced, substances have been employed, some of whose constituent parts have a strong attraction for phlogiston, and, as it would appear, a stronger for that substance than humor has they should, therefore, dephlogisticate the water or fixed air, and the humor thus set free should unite to the matter of fire and light and become pure air.74... 

My father says, I believe there is something in this phlogiston theory that may shed all kinds of light on the behavior of metals when heated or burned. We will next try the same experiment on sulfur, iron, and lead. Make a list. He pulls off his wig, throws it on the bench, puts it back on his head. 

Well, Father, I have been thinking about the phlogiston theory in the light of Boyle s investigations and our own experiments today. ... 

I don t know. I wish I did. I can only tell you what other people have said. Sir Isaac Newton, for instance, believes that light communicates heat to bodies by the vibrations of a medium he calls ether, hundreds of times more elastic than air so that it can penetrate even solid bodies. Robert Boyle, on the other hand, thought that fire is due to fiery corpuscles that exist in the air. And then the latest theory from the Continent is phlogiston. ... 

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