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.
[Illustration: 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.