Uncle Tungsten: Memories of a Chemical Boyhood (2001) (22 page)

My first vision was of metals, dozens of them in every possible form: rods, lumps, cubes, wire, foil, discs, crystals. Most were grey or silver, some had hints of blue or rose. A few had burnished surfaces that shone a faint yellow, and then there were the rich colors of copper and gold.

In the upper right corner were the nonmetals – sulphur in spectacular yellow crystals and translucent red crystals of selenium; phosphorus, like pale beeswax, kept under water; and carbon, as tiny diamonds and shiny black graphite. There was boron, a brownish powder, and ridged crystalline silicon, with a rich black sheen like graphite or galena.

On the left were the alkali and alkaline earth metals – the Humphry Davy metals – all (except magnesium) in protective baths of naphtha. I was struck by the lithium in the upper corner, for this, with its levity, was floating on the naphtha, and also by the cesium, lower down, which formed a glittering puddle beneath the naphtha. Cesium, I knew, had a very low melting point and it was a hot summer day. But I had not fully realized, from the tiny, partly oxidized lumps I had seen, that pure cesium was pale gold – it gave at first just a glint, a flash of gold, seeming to iridesce with a golden luster; then, from a lower angle, it was purely gold, and looked like a gilded sea, or golden mercury.

There were other elements which up to this point had only been names to me (or, almost equally abstract, names attached to some physical properties and atomic weights), and now for the first time I saw the range of their diversity and actuality. In this first, sensuous glance I saw the table as a gorgeous banquet, a huge table set with eighty-odd different dishes.

I had, by this time, become familiar with the properties of many elements and I knew they formed a number of natural families, such as the alkali metals, the alkaline earth metals, and the halogens. These families (Mendeleev called them ‘groups’) formed the verticals of the table, the alkali and alkaline earth metals to the left, the halogens and inert gases to the right, and everything else in four intermediate groups in between. The ‘groupishness’ of these intermediate groups was somewhat less clear – thus in Group VI, I saw sulphur, selenium, and tellurium. I knew that these three (my ‘stinkogens’) were very similar, but what was oxygen doing, heading the group? There must be some deeper principle at work – and indeed there was. This was printed at the top of the table, but in my impatience to look at the elements themselves, I had paid no attention to it at all. The deeper principle, I saw, was valency. The term
valency
was not to be found in my early Victorian books, for it had only been properly developed in the late 1850
s
, and Mendeleev was one of the first to seize on it and use it as a basis for classification, to provide what had never been clear before: a rationale, a basis for the fact that elements seemed to form natural families, to have deep chemical and physical analogies with one another. Mendeleev now recognized eight such groups of elements in terms of their valencies.

Thus the elements in Group I, the alkali metals, had a valency of 1: one atom of these would combine with one atom of hydrogen, to form compounds such as LiH, NaH, KH, and so on. (Or with one atom of chlorine, to form compounds such as LiCl, NaCl, or KC1). The elements of Group II, the alkaline earth metals, had a valency of 2, and so would form compounds such as CaCl
₂
, SrCl
₂
, BaCl
₂
, and so on. The elements of Group VIII had a maximum combining power of 8.

But while Mendeleev was organizing the elements in terms of valency, he was also fascinated by atomic weights and the fact that these were unique and specific to each element, that they were, in a sense, the atomic signature of each element. And if, mentally, he started to index the elements according to their valencies, he did this equally in terms of their atomic weights. And now, magically, the two came together. For if he arranged the elements, quite simply, in order of their atomic weights, in horizontal ‘periods,’ as he called them, one could see recurrences of the same properties and valencies at regular intervals.

Every element echoed the properties of the one above, was a slightly heavier member of the same family. The same melody, so to speak, was played in each period – first an alkali metal, then an alkaline earth metal, then six more elements, each with its own valency or tone – but played in a different register (it was impossible to avoid thinking of octaves and scales here, for I lived in a musical house, and scales were the periodicity I heard daily).

It was eightness which dominated the periodic table before me, though one could also see, in the lower part of the table, that extra elements were interposed within the basic octets: ten extra elements apiece in Periods 4 and 5, and ten plus fourteen in Period 6.

So one went up, each period completing itself and leading to the next one in a series of dizzying loops – at least this is the form my imagination took, so that the sober, rectangular table before me was transformed, mentally, into spirals or loops. The table was a sort of cosmic staircase or a Jacob’s ladder, going up to, coming down from, a Pythagorean heaven.

I got a sudden, overwhelming sense of how startling the periodic table must have seemed to those who first saw it – chemists profoundly familiar with seven or eight chemical families, but who had never realized the basis of these families (valency), nor how all of them might be brought together into a single over-arching scheme. I wondered if they had reacted as I did to this first revelation: ‘Of course! How obvious! Why didn’t I think of it myself?’

Whether one thought in terms of the verticals or in terms of the horizontals – either way one arrived at the same grid. It was like a crossword puzzle that could be approached by either the ‘down’ or the ‘across’ clues, except that a crossword was arbitrary, a purely human construct, while the periodic table reflected a deep order in nature, for it showed all the elements arrayed in a fundamental relationship. I had the sense that it harbored a marvelous secret, but it was a cryptogram without a key – 
why
was this relationship so?

I could scarcely sleep for excitement the night after seeing the periodic table – it seemed to me an incredible achievement to have brought the whole, vast, and seemingly chaotic universe of chemistry to an all-embracing order. The first great intellectual clarifications had occurred with Lavoisier’s defining of elements, with Proust’s finding that elements combined in discrete proportions only, and with Dalton’s notion that elements had atoms with unique atomic weights. With these, chemistry had come of age, and had become the chemistry of the elements. But the elements themselves were not seen to come in any order; they could only be listed alphabetically (as Pepper did in his
Playbook of Metals
) or in terms of isolated local families or groups. Nothing beyond this was possible until Mendeleev’s achievement. To have perceived an
overall
organization, a superarching principle uniting and relating
all
the elements, had a quality of the miraculous, of genius. And this gave me, for the first time, a sense of the transcendent power of the human mind, and the fact that it might be equipped to discover or decipher the deepest secrets of nature, to read the mind of God.

I kept dreaming of the periodic table in the excited half-sleep of that night – I dreamed of it as a flashing, revolving pinwheel or Catherine wheel, and then as a great nebula, going from the first element to the last, and whirling beyond uranium, out to infinity. The next day I could hardly wait for the museum to open, and dashed up to the top floor, where the table was, as soon as the doors were opened.

On this second visit I found myself looking at the table in almost geographic terms, as a realm, a kingdom, with different territories and boundaries. Seeing the table as a geographic realm allowed me to rise above the individual elements, and see certain general gradients and trends. Metals had long been recognized as a special category of elements, and now one could see, in a single synoptic glance, how they occupied three-quarters of the realm – all of the west side, most of the south – leaving only a smallish area, mostly in the northeast, for the nonmetals. A jagged line, like Hadrian’s Wall, separated the metals from the rest, with a few ‘semimetals,’ metalloids – arsenic, selenium – straddling the wall. One could see the gradients of acid and base, how the oxides of the ‘western’ elements reacted with water to form alkalis, the oxides of the ‘eastern’ elements, mostly nonmetals, to form acids. One could see, again at a glance, how the elements on either border of the realm – the alkali metals and halogens, like sodium and chlorine, for example – showed the greatest avidity for each other and combined with explosive force, forming crystalline salts with high melting points which dissolved to form electrolytes; while those in the middle formed a very different sort of compound – volatile liquids or gases which resisted electric currents. One could see, remembering how Volta and Davy and Berzelius ranked the elements into an electrical series, how the most strongly electropositive elements were all to the left, the most strongly electronegative to the right. Thus it was not just the placement of the individual elements, but trends of every sort that hit the eye when one looked at the table.

Seeing the table, ‘getting’ it, altered my life. I took to visiting it as often as I could. I copied it into my exercise book and carried it everywhere; I got to know it so well – visually and conceptually – that I could mentally trace its paths in every direction, going up a group, then turning right on a period, stopping, going down one, yet always knowing where I was. It was like a garden, the garden of numbers I had loved as a child – but unlike this, it was real, a key to the universe. I spent hours now, enchanted, totally absorbed, wandering, making discoveries, in the enchanted garden of Mendeleev.«40»

There was a photograph of Mendeleev next to the periodic table in the museum; he looked like a cross between Fagin and Svengali, with a huge mass of hair and beard and piercing, hypnotic eyes. A wild, extravagant, barbaric figure – but as romantic, in his way, as the Byronic Humphry Davy. I needed to know more of him, and to read his famous
Principles
, in which he had first published his periodic table.

His book, his life, did not disappoint me. He was a man of encyclopedic interests. He was also a music lover and a close friend of Borodin (who was also a chemist). And he was the author of the most delightful and vivid chemistry text ever published,
The Principles of Chemistry
.«41»

Like my own parents, Mendeleev had come from a huge family – he was the youngest, I read, of fourteen children. His mother must have recognized his precocious intelligence, and when he reached fourteen, feeling that he would be lost without a proper education, she walked thousands of miles from Siberia with him – first to the University of Moscow (from which, as a Siberian, he was barred) and then to St. Petersburg, where he got a grant to train as a teacher.

(She herself, apparently, nearing sixty at the time, died from exhaustion after this prodigious effort. Mendeleev, profoundly attached to her, was later to dedicate the
Principles
to her memory.)

Even as a student in St. Petersburg, Mendeleev showed not only an insatiable curiosity, but a hunger for organizing principles of all kinds. Linnaeus, in the eighteenth century, had classified animals and plants, and (much less successfully) minerals, too. Dana, in the 1830
s
, had replaced the old physical classification of minerals with a chemical classification of a dozen or so main categories (native elements, oxides, sulphides, and so on). But there was no such classification for the elements themselves, and there were now some sixty elements known. Some elements, indeed, seemed almost impossible to categorize. Where did uranium go, or that puzzling, ultralight metal, beryllium? Some of the most recently discovered elements were particularly difficult – thallium, for example, discovered in 1862, was in some ways similar to lead, in others to silver, in others to aluminium, and in yet others to potassium.

It was nearly twenty years from Mendeleev’s first interest in classification to the emergence of his periodic table in 1869. This long pondering and incubation (so similar, in a way, to Darwin’s before he published
On the Origin of Species
) was perhaps the reason why, when Mendeleev finally published his
Principles
, he could bring a vastness of knowledge and insight far beyond any of his contemporaries – some of them also had a clear vision of periodicity, but none of them could marshal the overwhelming detail he could.

Mendeleev described how he would write the properties and atomic weights of the elements on cards and ponder and shuffle these constantly on his long railway journeys through Russia, playing a sort of patience or (as he called it) ‘chemical solitaire,’ groping for an order, a system that might bring sense to all the elements, their properties and atomic weights.

There was another crucial factor. There had been considerable confusion, for decades, about the atomic weights of many elements. It was only when this was cleared up finally, at the Karlsruhe conference in 1860, that Mendeleev and others could even think of achieving a full taxonomy of the elements. Mendeleev had gone to Karlsruhe with Borodin (this was a musical as well as a chemical journey, for they stopped at many churches en route, trying out the local organs for themselves). With the old, pre-Karlsruhe atomic weights one could get a sense of local triads or groups, but one could not see that there was a numerical relationship
between
the groups themselves.«42» Only when Cannizzaro showed how reliable atomic weights could be obtained and showed, for example, that the proper atomic weights for the alkaline earth metals (calcium, strontium, and barium) were 40, 88, and 137 (not 20, 44, and 68, as formerly believed) did it become clear how close these were to those of the alkali metals – potassium, rubidium, and cesium. It was this closeness, and in turn the closeness of the atomic weights of the halogens – chlorine, bromine, and iodine – which incited Mendeleev, in 1868, to make a small grid juxtaposing the three groups: