Uncle Tungsten: Memories of a Chemical Boyhood (2001) (5 page)

The great virtue of the platinum metals was that while they were as noble and workable as gold, they had much higher melting points, and this made them ideal for chemical apparatus. Crucibles made of platinum could withstand the hottest temperatures; beakers and spatulas of it could withstand the most corrosive acids. Uncle Dave pulled out a small crucible from the cabinet, beautifully smooth and shiny. It looked new.

‘This was made around 1840,’ he said. ‘A century of use, and almost no wear.’

My grandfather’s oldest son, Jack, was fourteen years old in 1867, when diamonds were found near Kimberley in South Africa and the great diamond rush began. In the 1870
s
Jack, along with two brothers – Charlie and Henry (Henry was born deaf and used sign language) – went to make their lives and fortunes in South Africa as consultants in the diamond, uranium, and gold mines (their sister Rose accompanied them). In 1873 my grandfather remarried, and had thirteen more children, and the old family myths – a combination perhaps of his elder sons’ stories, Rider Haggard’s tales of
King Solomon’s Mines
and the old legends of the Valley of Diamonds – caused two of the next-born (Sydney and Abe) to join their half-brothers in Africa. Later still, two of the younger brothers, Dave and Mick, joined them as well, so at one point seven of the nine Landau brothers were working as mining consultants in Africa.

A photograph that hung in our house (and now hangs in mine) shows a family group taken in 1902 – Grandfather, bearded and patriarchal, his second wife, Chaya, and their thirteen children. My mother appears as a little girl of six or seven, and her youngest sister, Dooggie – the youngest of the eighteen – as a ball of fluff on the ground. The images of Abe and Sydney, one can see if one looks closely, have been grafted into place (the photographer had arranged the others to make spaces for them), for they were still in South Africa at the time – detained, and perhaps endangered, by the Boer War.²

The elder half-brothers, married and rooted now, stayed in South Africa. They never returned to England, though tales of them constantly circulated in the family, tales heightened to the legendary by the family mythopoeia. But the younger brothers – Sydney, Abe, Mick, and Dave – returned to England when the First World War broke out, armed with exotic tales and trophies of their mining days, including minerals of all sorts.

Uncle Dave loved handling the metals and minerals in his cabinet, allowing me to handle them, expatiating on their wonders. He saw the whole earth, I think, as a gigantic natural laboratory, where heat and pressure caused not only vast geologic movements, but innumerable chemical miracles too. ‘Look at these diamonds,’ he would say, showing me a specimen from the famous Kimberley mine. ‘They are almost as old as the earth. They were formed thousands of millions of years ago, deep in the earth, under unimaginable pressures. Then they were brought to the surface in this kimberlite, tracking hundreds of miles from the earth’s mantle, and then through the crust, very, very slowly, till they finally reached the surface. We may never see the interior of the earth directly, but this kimberlite and its diamonds are a sample of what it is like. People have tried to manufacture diamonds,’ he added, ‘but we cannot match the temperatures and pressures that are necessary.’³

On one visit. Uncle Dave showed me a large bar of aluminium. After the dense platinum metals, I was amazed at how light it was, scarcely heavier than a piece of wood. ‘I’ll show you something interesting,’ he said. He took a smaller lump of aluminium, with a smooth, shiny surface, and smeared it with mercury. All of a sudden – it was like some terrible disease – the surface broke down, and a white substance like a fungus rapidly grew out of it, until it was a quarter of an inch high, then half an inch high, and it kept growing and growing until the aluminium was completely eaten up. ‘You’ve seen iron rust – oxidizing, combining with the oxygen in the air,’ Uncle said. ‘But here, with the aluminium, it’s a million times faster. That big bar is still quite shiny, because it’s covered by a fine layer of oxide, and that protects it from further change. But rubbing it with mercury destroys the surface layer, so then the aluminium has no protection, and it combines with the oxygen in seconds.’

I found this magical, astounding, but also a little frightening – to see a bright and shiny metal reduced so quickly to a crumbling mass of oxide. It made me think of a curse or a spell, the sort of disintegration I sometimes saw in my dreams. It made me think of mercury as evil, as a destroyer of metals. Would it do this to every sort of metal?

‘Don’t worry,’ Uncle answered, ‘the metals we use here, they’re perfectly safe. If I put this little bar of tungsten in the mercury, it would not be affected at all. If I put it away for a million years, it would be just as bright and shiny as it is now.’ The tungsten, at least, was stable in a precarious world.

‘You’ve seen,’ Uncle Dave went on, ‘that when the surface layer is broken, the aluminium combines very rapidly with oxygen in the air to form this white oxide, which is called alumina. It is similar with iron as it rusts; rust is an iron oxide. Some metals are so avid for oxygen that they will combine with it, tarnishing, forming an oxide, the moment they are exposed to the air. Some will even pull the oxygen out of water, so one has to keep them in a sealed tube or under oil.’ Uncle showed me some chunks of metal with a whitish surface, in a bottle of oil. He fished out a chunk and cut it with his penknife. I was amazed at how soft it was; I had never seen a metal cut like this. The cut surface had a brilliant, silvery luster. This was calcium, Uncle said, and it was so active that it never occurred in nature as the pure metal, but only as compounds or minerals from which it had to be extracted. The white cliffs of Dover, he said, were chalk; others were made of limestone – these were different forms of calcium carbonate, a major component in the crust of the earth. The calcium metal, as we spoke, had oxidized completely, its bright surface now a dull, chalky white. ‘It’s turning into lime,’ Uncle said, ‘calcium oxide.’

But sooner or later Uncle’s soliloquies and demonstrations before the cabinet all returned to
his
metal. ‘Tungsten,’ he said. ‘No one realized at first how perfect a metal it was. It has the highest melting point of any metal, it is tougher than steel, and it keeps its strength at high temperatures – an ideal metal!’

Uncle had a variety of tungsten bars and ingots in his office. Some he used as paperweights, but others had no discernible function whatever, except to give pleasure to their owner and maker. And indeed, by comparison, steel bars and even lead felt light and somehow porous, tenuous. ‘These lumps of tungsten have an extraordinary concentration of mass,’ he would say. ‘They would be deadly as weapons – far deadlier than lead.’

They had tried to make tungsten cannonballs at the beginning of the century, he added, but found the metal too hard to work – though they used it sometimes for the bobs of pendulums. If one wanted to weigh the earth, Uncle Dave suggested, and to use a very dense, compact mass to ‘balance’ against it, one could do no better than to use a huge sphere of tungsten. A ball only two feet across, he calculated, would weigh five thousand pounds.

One of tungsten’s mineral ores, scheelite, Uncle Dave told me, was named after the great Swedish chemist Carl Wilhelm Scheele, who was the first to show that it contained a new element. The ore was so dense that miners called it ‘heavy stone’ or
tung sten
, the name subsequently given to the element itself. Scheelite was found in beautiful orange crystals that fluoresced bright blue in ultraviolet light. Uncle Dave kept specimens of scheelite and other fluorescent minerals in a special cabinet in his office. The dim light of Farringdon Road on a November evening, it seemed to me, would be transformed when he turned on his Wood’s lamp and the luminous chunks in the cabinet suddenly glowed orange, turquoise, crimson, green.

Though scheelite was the largest source of tungsten, the metal had first been obtained from a different mineral, called wolframite. Indeed, tungsten was sometimes called wolfram, and still retained the chemical symbol W. This thrilled me, because my own middle name was Wolf. Heavy seams of the tungsten ores were often found with tin ore, and the tungsten made it more difficult to isolate the tin. This was why, my uncle continued, they had originally called the metal wolfram – for, like a hungry animal, it ‘stole’ the tin. I liked the name
wolfram
, its sharp, animal quality, its evocation of a ravening, mystical wolf – and thought of it as a tie between Uncle Tungsten, Uncle Wolfram, and myself, O. Wolf Sacks.

‘Nature offers you copper and silver and gold native, as pure metals,’ Uncle would say, ‘and in South America and the Urals, she offers the platinum metals, too.’ He liked to pull out the native metals from his cabinet – twists and spangles of rosy copper; wiry, darkened silver; grains of gold panned by miners in South Africa. ‘Think how it must have been,’ he said, ‘seeing metal for the first time – sudden glints of reflected sunlight, sudden shinings in a rock or at the bottom of a stream!’

But most metals occurred in the form of oxides, or ‘earths.’ Earths, he said, were sometimes called calxes, and these ores were known to be insoluble, incombustible, infusible, and to be, as one eighteenth-century chemist wrote, ‘destitute of metallic splendour.’ And yet, it was realized, they were very close to metals and could indeed be converted into metals if heated with charcoal; while pure metals became calxes if heated in air. What actually occurred in these processes, however, was not understood. There can be a deep practical knowledge, Uncle said, long before theory: it was appreciated, in practical terms, how one could smelt ores and make metals, even if there was no correct understanding of what actually went on.

He would conjure up the first smelting of metal, how cavemen might have used rocks containing a copper mineral – green malachite perhaps – to surround a cooking fire and suddenly realized as the wood turned to charcoal that the green rock was bleeding, turning into a red liquid, molten copper.

We know now, he went on, that when one heats the oxides with charcoal, the carbon in the charcoal combines with their oxygen and in this way ‘reduces’ them, leaving the pure metal. Without the ability to reduce metals from their oxides, he would say, we would never have known any metals other than the handful of native ones. There would never have been a bronze age, much less an iron age; there would never have been the fascinating discoveries of the eighteenth century, when a dozen and a half new metals (including tungsten!) were extracted from their ores.

Uncle Dave showed me some pure tungstic oxide obtained from scheelite, the same substance as Scheele and the d’Elhuyars, the discoverers of tungsten, had prepared.«4» I took the bottle from him; it contained a dense yellow powder that was surprisingly heavy, almost as heavy as iron. ‘All we need to do,’ he said, ‘is heat it with some carbon in a crucible until it’s red-hot.’ He mixed the yellow oxide and the carbon together, and put the crucible in a corner of the huge furnace. A few minutes later, he withdrew it with long tongs, and as it cooled, I was able to see that an exciting change had occurred. The carbon was all gone, as was most of the yellow powder, and in their place were grains of dully shining grey metal, just as the d’Elhuyars had seen in 1783.

‘There’s another way we could make it,’ Uncle said. ‘It’s more spectacular.’ He mixed the tungstic oxide with finely powdered aluminium, and then placed some sugar, some potassium perchlorate, and a little sulphuric acid on top. The sugar and perchlorate and acid took fire at once, and this in turn ignited the aluminium and tungstic oxide, which burned furiously, sending up a shower of brilliant sparks. When the sparks cleared, I saw a white-hot globule of tungsten in the crucible. ‘That is one of the most violent reactions there is,’ said Uncle. ‘They call this the thermite process; you can see why. It can generate a temperature of three thousand degrees or more – enough to melt the tungsten. You see I had to use a special crucible lined with magnesia, to withstand the temperature. It’s a tricky business, things can explode if you’re not careful – and in the war, of course, they used this process to make incendiary bombs. But if conditions are right, it’s a wonderful method, and it has been used to obtain all the difficult metals – chromium, molybdenum, tungsten, titanium, zirconium, vanadium, niobium, tantalum.’

We scraped out the tungsten grains, washed them carefully with distilled water, examined them with a magnifying glass, and weighed them. He pulled out a tiny, 0.5-milliliter graduated cylinder, filled it to the 0.4-milliliter mark with water, then tipped in the tungsten grains. The water rose a twentieth of a milliliter. I jotted down the exact figures, and worked them out – the tungsten weighed a little less than a gram, and had a density of 19. ‘That’s very good,’ Uncle said, ‘that’s pretty much what the d’Elhuyars got when they first made it back in the 1780
s
.

‘Now I’ve got several different metals here, all in little grains. Why don’t you get some practice weighing these, measuring their volume, working out their density?’ I spent the next hour delightedly doing this and found that Uncle had indeed given me a huge range, from one silvery metal, a little tarnished, which had a density of less than 2, to one of his osmiridium grains (I recognized it), which was almost a dozen times as dense. When I measured the density of a little yellow grain, it was exactly the same as that of tungsten – 19.3, to be exact. ‘You see,’ said Uncle, ‘gold’s density is almost the same as tungsten’s, but silver is much lighter. It is easy to feel the difference between pure gold and gilded silver – but you would have a problem with gold-plated tungsten.’

Scheele was one of Uncle Dave’s great heroes. Not only had he discovered tungstic acid and molybdic acid (from which the new element molybdenum was made), but hydrofluoric acid, hydrogen sulfide, arsine, and prussic acid, and a dozen organic acids, too. All this, Uncle Dave said, he did by himself, with no assistants, no funds, no university position or salary, but working alone, trying to make ends meet as an apothecary in a small provincial Swedish town. He had discovered oxygen, not by a fluke, but by making it in several different ways; he had discovered chlorine; and he had pointed the way to the discovery of manganese, of barium, of a dozen other things.