Читать книгу Modern Alchemy and the Philosopher's Stone - Wilfried B. Holzapfel - Страница 26

“I don’t particularly like either of these models in terms of the way in which they represent the atoms themselves, Professor Wood remarked. “We do not think of atoms as having hard surfaces like these balls. According to our current conceptual model of an atom, the electrons form what we think of as clouds that do not a have a well-defined outer surface. They are more nebulous with slowly decreasing density and can “adjust” to the shape of the platonic bodies.

“Nonetheless,” he continued, “these models are useful in describing the spatial relationships among the centers of the atoms whose locations are represented by the centers of the balls in these models. As you can see, the spheres and rods form what we now refer to as a lattice. For theoretical purposes, we consider this lattice to extend indefinitely across the bulk of crystal or a specimen. In the journeys that I am suggesting we take, we will examine the effects of compressing the lattice by applying equal force to all of the exposed surfaces. We use the term hydrostatic pressure to describe a force that is distributed uniformly over all of the exposed surfaces of a solid object.”

Professor Wood noticed that the shadow of frown had returned to Helen’s face. “But, for now,” he said, “let’s just concentrate on the idea of a crystal lattice that is made up of a single kind of atom. That would be a pure elemental crystal, without any impurities or lattice irregularities.”

“Irregularities?” Helen asked.

“I mean things that might be represented in this kind of model by a section having a bent, broken or missing stick,” the professor said. “There might even be an atom that is missing or misplaced.”

The frown on Helen’s face disappeared.

“In the crystal lattice of a diamond,” the professor explained, “each atom has strong bonds to four nearest neighbors. If you can imagine the smallest crystal blocks which fill the whole space without any gaps, you get the form of the truncated tetrahedron shown here to the right of the stick and ball figure.

“As you can see,” he continued, “the four large hexagonal surfaces of this body divide the connecting lines to the four nearest neighbors exactly in half, and the six small triangles truncate this tetrahedron in such a way that these triangles intersect the connecting lines in the middle to the 6 second-nearest neighbors.”

Helen was intrigued. “These pictures do really reflect the ideas of the ancient Greeks!” she exclaimed.

Professor Wood continued, “The Greeks thought about atoms in terms of bodies that have solid surfaces. Today we think of these surfaces as the result of artificially constructed boundaries between neighboring atoms in a solid. Each atom, in turn, consists of a nucleus surrounded by electrons with some kind of shell structure where only the most weakly-bound outer electrons, the so called valence electrons, are involved in the bonding with neighboring atoms. That is more or less what is implied by the word covalent that someone has added below the word sulfur on the figure that you showed us, Marie.

“Sulfur is an example of a naturally occurring substance that is comprised of just one element. The sulfur atoms are locked into a fairly rigid lattice using covalent chemical bonds. Sulfur does not form bonds as rigid as the ones in carbon. That is reflected in the fact that pure sulfur feels soft to us and easy to pulverize, unlike diamond which is the epitome of a hard substance. Diamond might equally have appeared in the diagram from Basil Valentine, but diamond was probably outside the experience of the average alchemist in those times.”

“I see now what you meant when you said that the Platonic solids have found their way into modern alchemy!” Helen remarked.

The professor was quite pleased. “Very good, Helen,” he said. “We find many pictures like this in modern books of physicists or crystallographers. But in the modern books the authors refer to Wigner-Seitz cells. Two physicists, Eugene Wigner and Frederick Seitz constructed models just like this for many simple crystals to help them describe the properties of the crystals in a simple way.”

Helen and Marie exchanged glances. They had never taken the opportunity to speak with one of their professors person-to-person. And this was not even one of their instructors. Neither of them was enrolled in Professor Wood’s course. But he seemed eager to share his knowledge of materials science and its history with them. They felt flattered and quite privileged to have this opportunity to learn something quite special. Neither of them had ever really thought much about how crystals are formed or how scientists classify them.

“I would very much like to meet with you again next week,” Marie volunteered. “We haven’t even mentioned metallic bonding yet, except to point out that someone had written the word metallic next to covalent on the diagram by Basil Valentine.”

“And I am curious about the other ways in which the ancient alchemists seem to have foreseen some of the more esoteric aspects of modern science,” Helen added.

“Very well, then, I shall look forward to seeing you next week. Don’t forget to sign up for the time on the sheet outside the door on your way out.”

When they got to the dorm, the two friends went immediately to Marie’s room and fired up her computer. They revisited some of the sites on alchemy that they had previously found.

“Look here,” Marie pointed out excitedly. “It says that being and becoming, eternal and ephemeral, resting and moving, were all very important terms for the world of the alchemists.” She read aloud further, “Insemination, birth, growth, maturation, associations with death and decay, with soul and body were terms used to describe the chemical processes in the alchemy. Our concept of essence, for example, dates from this period and is derived from the Latin word esse, meaning to be. For the alchemists, Essentia referred to the fundamental, immutable nature of a thing. In all life cycles there must be an essence, something that endures eternally. This way of thinking led the Greeks to the four elements that we have been talking about – the four Essentia of the alchemists: Earth, Water, Air and Fire.”

Helen found another figure that she liked from a German source (Figure 11). She used her smart phone to access an online translation program to get the English meaning of the terms that appear around the figure: feucht = wet; trocken = dry; kalt = cold.