He had developed and patented a luminous paint, and this was used in military gunsights in the First World War (it may have been decisive, he told me, in the Battle of Jutland). His paints were also used to illuminate the dials of Ingersoll watches and clocks. He had, like Uncle Dave, big, capable hands, but where Uncle Dave’s were seamed with tungsten, Uncle Abe’s were covered with radium burns and malignant warts from his long, careless handling of radioactive materials.
Both Uncle Dave and Uncle Abe were intensely interested in light and lighting, as was their father; but with Dave it was ‘hot’ light, and with Abe ‘cold’ light. Uncle Dave had drawn me into the history of incandescence, of the rare earths and metallic filaments which glowed and incandesced brilliantly when heated. He had inducted me into the energetics of chemical reactions – how heat was absorbed or emitted during the course of these; heat that sometimes became visible as fire and flame.
Through Uncle Abe, I was drawn into the history of ‘cold’ light – luminescence – which started perhaps before there was any language to record things, with observations of fireflies and glowworms and phosphorescent seas; of will-o’ – the-wisps, those strange, wandering, faint globes of light that would, in legend, lure travelers to their doom. And of Saint Elmo’s fire, the eerie luminous discharges that could stream in stormy weather from a ship’s masts, giving its sailors a feeling of bewitchment. There were the auroras, the Northern and Southern Lights, with their curtains of color shimmering high in the sky. A sense of the uncanny, the mysterious, seemed to inhere in these phenomena of cold light – as opposed to the comforting familiarity of fire and warm light.
There was even an element, phosphorus, which glowed spontaneously. Phosphorus attracted me strangely, dangerously, because of its luminosity – I would sometimes slip down to my lab at night to experiment with it. As soon as I had my fume cupboard set up, I put a piece of white phosphorus in water and boiled it, dimming the lights so that I could see the steam coming out of the flask, glowing a soft greenish blue. Another, rather beautiful experiment was boiling phosphorus with caustic potash in a retort – I was remarkably nonchalant about boiling up such virulent substances – and this produced phosphoretted hydrogen (the old term), or phosphine. As the bubbles of phosphine escaped, they took fire spontaneously, forming beautiful rings of white smoke.
I could ignite phosphorus in a bell jar (using a magnifying glass), and the jar would fill with a ‘snow’ of phosphorus pentoxide. If one did this over water, the pentoxide would hiss, like red-hot iron, as it hit the water and dissolved, making phosphoric acid. Or by heating white phosphorus, I could transform it into its allotrope, red phosphorus, the phosphorus of matchboxes.[52] I had learned as a small child that diamond and graphite were different forms, allotropes, of the same element. Now, in the lab, I could effect some of these changes for myself, turning white phosphorus into red phosphorus, and then (by condensing its vapor) back again. These transformations made me feel like a magician.[53]
But it was especially the luminosity of phosphorus that drew me again and again. One could easily dissolve some of it in clove oil or cinnamon oil, or in alcohol (as Boyle had done) – this not only overcame its garlicky smell, but allowed one to experiment with its luminosity safely, for such a solution might contain only one part of phosphorus in a million, and yet still glow. One could rub a bit of this solution on one’s face or hands, and they would glow, ghostlike, in the dark. This glow was not uniform, but seemed (as Boyle had put it) ‘to tremble much, and sometimes… to blaze out with sudden flashes.’
Hennig Brandt of Hamburg had been the first to obtain this marvelous element, in 1669. He distilled it from urine (apparently with some alchemical ambition in mind), and he adored the strange, luminous substance he had isolated, and called it cold fire (kaltes Feuer), or, in a more affectionate mood, mein Feuer.
Brandt handled his new element rather carelessly, and was apparently surprised to discover its lethal powers, as he wrote in a letter to Leibniz on April 30, 1679:
When in these days I had some of that very fire in my hand and did nothing more than blow on it with my breath, the fire ignited itself as God is my witness; the skin on my hand was burned truly into a hardened stone such that my children cried and declared that it was horrible to witness.
But though all the early researchers burned themselves severely with phosphorus, they also saw it as a magical substance that seemed to carry within itself the radiance of glowworms, perhaps of the moon, a secret, inexplicable radiance of its own. Leibniz, corresponding with Brandt, wondered whether the glowing light of phosphorus could be used for lighting rooms at night (this, Abe told me, was perhaps the first suggestion of using cold light for illumination).
No one was more intrigued by this than Boyle, who made detailed observations of its luminescence – how it, too, required the presence of air, how it fluctuated strangely. Boyle had already made extensive investigations of ‘luciferous’ phenomena, from glowworms to luminous wood and tainted meat, and had made careful comparisons of such ‘cold’ light with that of glowing coals (both, he found, needed air to sustain them).
On one occasion Boyle was called down from his bedchamber by his frightened and astonished servant, who reported that some meat was glowing brightly in the dark pantry. Boyle, fascinated, got up at once and commenced an investigation, which culminated in his charming paper ‘Some Observations about Shining Flesh, both of Veal and Pullet, and that without any sensible Putrefaction in those Bodies.’ (The shining was probably due to luminescent bacteria, but no such organism was known or suspected in Boyle’s time.)
Uncle Abe, too, was fascinated by such chemical luminescence, and had experimented a great deal with it as a young man, and with luciferins, the light-producing chemicals of luminous animals. He had wondered whether they could be turned to practical use, to make a really brilliant luminous paint. Chemical luminosity could indeed be dazzlingly brilliant; the only problem was that it was ephemeral, transient, by nature, disappearing as soon as the reactants were consumed – unless there could be (as with fireflies) a continued production of the luciferous chemicals. If chemistry was not the answer, then one needed some other form of energy, something that could be transformed into visible light.
Abe’s interest in luminescence had been stimulated, when he was growing up, by a luminous paint used in their old house in Leman Street – Balmain’s Luminous Paint, it was called – for painting keyholes, gas and electric fixtures, anything that had to be located in the dark. Abe found these glowing keyholes and switches wonderful, the way they glowed softly for hours after being exposed to light. This sort of phosphorescence had been discovered in the seventeenth century, by a shoemaker in Bologna who had gathered some pebbles, roasted them with charcoal, and then observed that they glowed in the dark for hours after they had been exposed to daylight. This ‘phosphorus of Bologna’, as it was called, was barium sulphide, produced by the reduction of the mineral barytes. Calcium sulphide was easier to procure – it could be made by heating oyster shells with sulphur – and this, ‘doped’ with various metals, was the basis of Balmain’s Luminous Paint. (These metals, Abe told me, added in minute amounts, ‘activated’ the calcium sulphide, and lent it different colors as well. Perfectly pure calcium sulphide, paradoxically, did not glow.)
52
Uncle Abe told me something of the history of matches, how the first matches had to be dipped into sulphuric acid to light them before ‘lucifers’ – friction matches – were introduced in the 1830s, and how this led to a huge demand for white phosphorus over the next century. He told me of the awful conditions under which match girls worked in the factories and of the terrible disease, ‘phossy-jaw,’ they often got, until the use of white phosphorus was banned in 1906. (Only red phosphorus, far more stable, and far safer, was subsequently used.)
Abe also spoke of the hellish phosphorus bombs used in the Great War, and how there was a move to ban these, as poison gas had been banned. But now, in 1943, they were being used freely once again, and thousands of people on both sides were being burned alive in the most agonizing way possible.
53
Phosphorus, oxidizing slowly, was not the only element to glow when exposed to air. Sodium and potassium did this too, when they were freshly cut, but lost their luminosity in a few minutes as the cut surfaces tarnished. I found this by chance as I was working in my lab late one afternoon, as it gradually darkened into dusk – I had not yet switched on the light.