Elements and Phlogiston.

The ancient idea that earth, air, fire, and water were the elements of Nature was held by chemists in the 18th century. Empedocles appears to have been the author of this theory, which was adopted by Aristotle. Some speculative philosophers, however, taught that all of these were derived from one original first principle; some held that this was water, some earth, some fire, and others air. Paracelsus, who does not seem to have objected to this idea, contributed another fantastic one to accompany it. According to him everything was composed of sulphur, salt, and mercury; but he did not mean by these the material sulphur, salt, and mercury as we know them, but some sort of refined essence of these. These three essentials came to be tabulated thus:—

Salt.Sulphur.Mercury.
Unpleasant and bitter.Sweet.Acid.
Body.Soul.Spirit.
Matter.Form.Idea.
Patient.Agent.Informant or movent.
Art.Nature.Intelligence.
Sense.Judgment.Intellect.
Material.Spiritual.Glorious.

This is taken from Beguin, who explains that the mercury, sulphur, and salt of this classification are not those “mixt and concrete bodies such as are vulgarly sold by merchants. Mercury, which combines the elements of air and water, Sulphur represents Fire, and Salt, Earth.” “But the said principles, to speak properly, are neither bodies; because they are plainly spiritual, by reason of the influx of celestial seeds, with which they are impregnated: nor spirits, because corporeal, but they participate of either nature; and have been insignized by Phylosophers with various names, or at the least unto them they have alluded these.”

Instances of the combination of these principles are given. If you burn green woods, you first have a wateriness, mercury; then there goes forth an oleaginous substance easily inflammable, sulphur; lastly, a dry and terrestrial substance remains, salt. Milk contains a sulphurous buttery substance; mercurial, whey; saline, cheese. Eggs: white, mercury, yolk, sulphur, shell, salt. Antimony regulus, mercury, red sulphur conceiving flame; a salt which is vomitive.

George Ernest Stahl.

Born at Anspach, 1660; died at Berlin, 1734. Stahl was the originator of the “phlogiston theory” which generally prevailed in chemistry until Lavoisier disproved it in the last quarter of the 18th century.

Nowhere do you get these principles pure. Mercury (the metal) contains both sulphur and salt; so with the others.

Becker, the predecessor of Stahl, was not quite satisfied with the orthodox opinion, and improved upon it by limiting the elements to water and earth; but he recognised three earths, vitrifiable, inflammable, and mercurial. The last yielded the metals. Stahl was inclined to go back to the four elements again, but he had his doubts about their really elementary character. He, however, concentrated his attention on fire, out of which he evolved his well-known phlogiston theory. This substance, if it was a substance, was conceived as floating about all through the atmosphere, but only revealing itself by its effects when it came into contact with material bodies. There was some doubt whether it possessed the attribute of weight at all; but its properties were supposed to be quiescent when it became united with a substance which thereby became phlogisticated. It needed to be excited in some special way before it could be brought again into activity. When combined it was in a passive condition.

The amusing features of the phlogiston theory only developed when it came to be realised that when the phlogiston was driven out of a body, as in the case of the calcination of a metal, the calx remaining was heavier than the metal with the phlogiston had been. The first explanation of this phenomenon was that phlogiston not only possessed no heaviness, but was actually endowed with a faculty of lightness. This hypothesis was, however, a little too far-fetched for even the seventeenth century. Boerhaave thereupon discovered that as the phlogiston escaped it attacked the vessel in which the metal was calcined, and combined some of that with the metal. This notion would not stand experiment, but Baume’s explanation of what happened was singularly ingenious. He insisted that phlogiston was appreciably ponderable. But, he said, when it is absorbed into a metal or other substance it does not combine with that substance, but is constantly in motion in the interstices of the molecules. So that as a bird in a cage does not add to the weight of the cage so long as it is flying about, no more does phlogiston add to the weight of the metal in which it is similarly flying about. But when the calcination takes place the dead phlogiston, as it may be called, does actually combine with the metal, and thus the increase of weight is accounted for.