A is for Arsenic (30 page)

The 1937 novel
Dumb Witness
⁷⁸
is the only Agatha Christie story to use phosphorus as the means of murder. On the book's very first page Miss Arundell, a wealthy old spinster, dies, apparently of natural causes. She has been in delicate health for more than a year, after a near-fatal case of jaundice. The symptoms of her final illness suggest another attack of the same liver complaint, and the cause of death is officially recorded as yellow atrophy of the liver. Nothing seems out of the ordinary until the reading of the will. The sole beneficiary is Miss Arundell's companion, Minnie Wilson, who has only recently been appointed to the role. Miss Arundell's relatives, who all seem to be heavily in debt and highly unscrupulous, have been overlooked.

Although there was nothing medically to suggest that Miss Arundell was murdered, the circumstances surrounding her death and the behaviour of her family make Hercule Poirot suspicious. Together with Captain Hastings, Poirot carries out an unofficial investigation to prove that Miss Arundell was murdered. One of the more important clues comes from a seance Miss Arundell took part in just days before her death, when a strange halo of light formed around her head. Was it an apparition of ectoplasm? A spectral premonition of death? Or the eerie glow of luminescent phosphorus from the poison she had just swallowed?

The phosphorus story

Phosphorus comes in several different forms usually distinguished by their colour – white, red, violet and black. White phosphorus was the first to be discovered, with credit usually given to Hennig Brand,
⁷⁹
an alchemist working in the latter half of the seventeenth century. Others may perhaps have
made the discovery earlier, but Brand has by far the best story. Brand was in search of gold and, for reasons best known to himself, decided to search for it in urine (perhaps the colour was the clue). After collecting many buckets of his own urine he allowed the liquid to stagnate until worms started to grow in the festering fluid. The liquid was then boiled down to a thick paste – probably by an assistant, rather than by Brand himself. The paste was heated again under a hotter flame to produce a red oil, a black spongy layer and a white solid. The white solid tasted salty, and was thrown away. Unknown to Brand, the white solid actually contained most of the phosphorus, in the form of phosphate salts. Brand continued his experiments, and combined the red oil and black layer before heating them again. From this mixture came white fumes that Brand collected in a glass vessel containing water. The fumes condensed to form a white, waxy solid. There was no gold, but what he had produced glowed in the dark. It is the glow that gives phosphorus its name, after the Greek for ‘light bearer'. At this time very few substances were known to emit light without the accompanying heat of a flame, so the substance was of some worth.

Brand's method was highly inefficient, producing only a 1 per cent yield of phosphorus from the gallons of urine that had to be collected and stored. The worm stage was also unnecessary; phosphorus can be produced from fresh urine as easily, and rather less unpleasantly, as from stagnant, worm-infested urine. However, Brand had succeeded in isolating a new element, only the 13th to be discovered of the 92 naturally occurring ones in the periodic table, and the first to be found since ancient times. Brand never revealed his method for producing phosphorus, but he was happy to sell lumps of it when he was short of funds. He did, however, let on that the source of this wondrous substance was human in origin, and a few others managed to work out Brand's method for themselves.

One person who worked out how to produce phosphorus was Daniel Kraft, a renowned German chemist of the same era. Kraft started demonstrating the properties of this new substance
at scientific gatherings. The lights would be turned out and small quantities of phosphorus were then smeared onto the face and the backs of the hands to demonstrate the strange glow of this substance, which was emitted without any noticeable heat. Phosphorus smeared on to a piece of paper would be warmed gently, causing the paper to catch fire where phosphorus was present. One such gathering took place for a few select members of the Royal Society in London, one September evening in 1677. Among the assembled gentlemen was Robert Boyle (1627–1691). Boyle, known today as the ‘Father of Modern Chemistry', was, at that time, an alchemist, searching for the philosopher's stone.
⁸⁰
Kraft's demonstration of phosphorus inspired and fascinated Boyle, and led him to carry out painstaking and detailed experiments to learn all he could about its mysterious properties. The systematic approach adopted by Boyle, and the accessible way he wrote up his experiments, helped him become a highly respected, world-renowned scientist. But to carry out his experiments, Boyle needed a supply of phosphorus. By 1680 Boyle had worked out the process, and collected all the urine from his house in Pall Mall, London. Together with his assistant Ambrose Godfrey (1660–1741), he processed the urine to maintain a steady supply of phosphorus for his experiments.

After leaving Boyle's employment, Godfrey continued to refine the method. Working in his laboratory just off the Strand in London, he produced the best white phosphorus, which he then supplied to Europe and beyond. Godfrey's source of phosphorus was still urine; anyone living near his lab had to put up with the smell, until after 1769, when Johann Gottlieb Gahn (1745–1818) and Carl Wilhelm Scheele (of Scheele's
Green fame; see page
here
) realised that phosphorus could also be obtained from bone ash.

White phosphorus is made up of units of simple molecules, consisting of four phosphorus atoms bonded together (P
4
). White phosphorus is not soluble in water, but it is soluble in oils and fats. It can turn yellow when stored for a long time, so it is sometimes called yellow phosphorus, but both yellow and white phosophorus refer to the same thing. This form of phosphorus is highly reactive, particularly with oxygen, so it is stored under water. White phosphorus will easily react with oxygen in the air, burning to form clouds of white phosphorus oxides. Burning phosphorus generates an intense amount of heat as well as smoke, which led to its use in incendiary bombs and as a smoke screen in warfare.

Many people have tried to utilise phosphorus's light-emitting properties to devise safe systems of lighting. They all failed, because of the extreme flammability of phosphorus. Even if the fire risks could be reduced, the process of generating phosphorus's eerie glow also produces an unpleasant garlicky smell.
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Phosphorus lighting was therefore both hazardous and unpleasant to live with. However, the flammable properties of white phosphorus were a positive benefit in its main household use, matches. White phosphorus was first used to make matches around 1830, and by the middle of the nineteenth century matches, with white phosphorus forming as much as 20 per cent of the match-head, were produced by the billion. The matches were easy to light, but also prone to igniting unexpectedly. For example, the heat of friction produced from treading on a match could cause a person to go up in flames, as happened to the 19-year-old Archduchess Matilda in 1867.
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Indeed, carrying a box of matches in your pocket could generate enough friction from the matches rubbing against each other inside the box to cause them to catch light. Even matches left on a window sill could ignite when the sun's rays fell on them.

From the 1840s onwards, safety matches were produced using red phosphorus instead of the white form. The red phosphorus was stuck to the side of the matchbox, and the friction from running the match-head along the box would cause enough heat for the match to catch light. Red phosphorus is produced by heating white phosphorus at high temperatures (in the absence of air), causing the small P
4
molecules to link into chains. Red phosphorus is much less volatile and less flammable than white phosphorus, and non-toxic. However, it is also more expensive, so at first safety matches didn't really catch on. Concerns about the safety of white phosphorus were raised as early as the 1850s but its use in matches wasn't banned until 1906.

To produce the huge number of white phosphorus matches needed to meet demand required a large workforce, working long hours in uncomfortable and often dangerous conditions. The danger of these matches lay not just in their flammability but in the toxic nature of the white phosphorus needed to produce them. Sticks of poplar wood, twice the length of the final match, would be arranged in racks and bound tightly. It was then the task of a ‘dipper' to dip both sides of the sticks in ‘the compound', with the racks of matches then dried in an oven. The matches would then be cut in half and boxed up, ready to sell. ‘The compound', a mixture of glue, colourant, sulfur and white phosphorus dissolved in water and heated by steam to maintain the right consistency, was held in shallow trays just the right depth for dipping the match-heads. A
skilled dipper could produce an astonishing 10 million matches in a single ten-hour shift. All the time the dippers would be breathing in phosphorus fumes, and those employed to box up the matches would be breathing in phosphorus dust.

White phosphorus is highly toxic and, in around 20 per cent of the workers, it would cause a condition known as ‘phossy jaw'. This would start off as a toothache, then the teeth would fall out, and the gums, jaw and face would become painful and swollen. Slowly the soft tissue and bone were eroded away. Abscesses would appear on the gum that would ooze a most foul-smelling pus. Further abscesses would appear along the jaw line, forming a wound through which could be seen the dead bone of the jaw. The only treatment for phossy jaw was the removal of the jaw bone, replacing it with an artificial jaw. Without this procedure the phosphorus would go on to cause damage to the internal organs, leading to death. Around 5 per cent of phossy jaw sufferers died from its effects. A study in France found that half of the people suffering from phossy jaw committed suicide rather than put up with the pain and foul stench of the condition.

Other than removing an individual from the source of poisoning there is very little that can be done to treat phosphorus poisoning. Thankfully, the chances of being exposed to white phosphorus today are very low. The tragedies that occurred in match factories led to hugely improved working conditions in many industries, not just in match-making, and exposure to white phosphorus fumes in the workplace is thankfully a thing of the past.

It could take years of environmental exposure to white phosphorus before phossy jaw developed, and even then the result would be far from guaranteed so, from a murderer's point of view, something more rapid and reliable would be necessary. Phosphorus can be absorbed through the skin and
gastrointestinal tract as well as through the walls of the lungs. The reactive nature of white phosphorus causes burns, so skin absorption will leave behind a nasty injury. Those working with incendiary bombs in the past had skin burns treated with copper sulfate solution. This is effective in neutralising the effects of phosphorus but copper sulfate is also toxic, and its use in this treatment has mostly been discontinued. Burns on the skin are likely to arouse suspicion, so the usual approach from a poisoner's point of view would be ingestion. If the intent is to murder an individual this is the most reliable route; even small quantities of around 100mg will be fatal.
⁸³

The toxic effects of phosphorus were recognised early on; Eilhard Mitscherlich (1794–1863), a Prussian chemist, was the first to suggest the use of phosphorus in a paste as a rat poison. He was also aware that humans might use poison intended for rats to dispose of other unwanted ‘pests'. Mitscherlich wrote a paper describing a method for the detection of phosphorus in cases of possible poisoning. The method, now known as the Mitscherlich test, consists of taking the substance suspected of containing phosphorus and heating it with water in a flask. The steam vaporises the phosphorus, which is then cooled and collected in a condenser. By viewing the apparatus in a darkened room the glow of phosphorus can be observed.