A is for Arsenic (10 page)

It is difficult to establish the dose Hugh must have been receiving, as we do not know how big the tub of cream was, or how much he used per day. Hugh must have been exposed to a larger daily dose than that designed to treat his father's eye condition in order to experience toxic effects. The amount of atropine sulfate absorbed through intact skin is usually very low, but the abrasive effect of shaving would have made the chemical far easier to absorb when the cream was applied to broken skin. As the poison took effect a rash appeared on Hugh's face, which would have allowed even more atropine sulfate to be absorbed – and probably caused him to apply yet more of the tainted face cream. Poirot's intervention and prevention of further poisoning saves Hugh's life; from what we know of this chemical, we can expect that he would go on to make a full recovery, and marry his betrothed, Miss Diana Maberley.

Notes

²⁵
The same effect is achieved by candlelight, because the pupil opens to allow more light into the eye to compensate for low light levels, hence the romance of a candle-lit dinner.

²⁶
Entitled
Murder in Three Acts
in the United States.

²⁷
Adding an acid to the alkali atropine will make the corresponding salt. For example, by adding hydrochloric acid, atropine chloride is formed.

²⁸
This is responsible for controlling automatic functions outside conscious control, such as the heart rate, salivation and certain reflex actions, such as coughing.

²⁹
Although
l
-hyoscyamine, one of the ‘hands' of atropine, is increasingly used, probably because it has fewer side effects.

³⁰
Miosis is an excessive constriction of the pupil that can be caused by several medical conditions.

³¹
This short story is part of a collection entitled
The Thirteen Problems
. This was called
The Tuesday Club Murders
in the United States.

³²
Hopefully in judiciously small quantities, to stop the pathologist from succumbing to the same poison. This is no longer considered a reliable method of identification.

³³
Mainly because Hitler couldn't believe that the Allies didn't have their own similar, but larger, stockpiles; the Allies did indeed have their own versions of organophosphorus-based chemical weapons, but again they were never used.

Sparkling Cyanide

The Strongest Poison ever known

Came from Caesar's Laurel Crown…

William Blake,
Auguries of Innocence

CYANIDE makes an appearance in no less than ten Agatha Christie novels and four short stories, where she uses it to bump off 18 characters. Christie had her murderers administer the poison in inventive and effective ways, including by injection, in drinks, in smelling salts and even in a cigarette. Her descriptions of the poison, the symptoms displayed by the victims and the possible sources of cyanide exhibit a high degree of accuracy. Rather than cataloguing the murders one after another, I'm going to focus on one book in particular, and that of course has to be
Sparkling Cyanide
.

Sparkling Cyanide
, or
Remembered Death
in the United States, was written by Christie in 1945. The story centres on the
well-to-do Barton family and a small group of friends, acquaintances and hangers-on. The novel opens with the recollection of events surrounding the dramatic death of Rosemary Barton at the Luxembourg restaurant by those who witnessed it. Seven people had dined together to celebrate a birthday; the lights went up after the cabaret, Barton took a sip from her champagne glass and then dropped dead, face down on the table, with her face blue and fingers twitching from convulsions. It was declared that death was from potassium cyanide poisoning, and the verdict was suicide.

Six months later, Rosemary's husband George Barton receives an anonymous note suggesting that Rosemary was murdered. Rather than do the sensible thing and tell the police, George embarks on an elaborate but insane plan to expose his wife's murderer. Exactly one year after the dreadful ‘suicide', George gathers together the six diners who were present at the original party. George also hires an actress, made up to look like Rosemary, with the idea being to have her appear during the dinner and startle a confession out of the murderer. The plan fails spectacularly; when George drinks a toast to the memory of his late wife he suddenly turns purple and falls flat on the table. It takes one and a half minutes for him to die, his drink being laced with the same poison as his wife's, one year previously. Fortunately, George had revealed some of his suspicions and plans to his friend, Colonel Race, an intelligence officer, who then works with the police to solve the crime.

In 1945, many poisons were terrifyingly easy to obtain and few antidotes were available. Thankfully things have changed, but cyanide still has a reputation as a horrible and frighteningly effective poison – and with good reason.

The cyanide story

The name ‘cyanide' comes from the Greek word
kyanos
meaning ‘dark blue', but by quite a roundabout route. Prussian Blue ([Fe
7
(CN)
18
]), an intense blue pigment commonly used by artists, was the compound used in 1752 to produce hydrogen cyanide (HCN), or prussic acid as it was called, by the French
chemist Pierre Macquer (1718–1784). ‘Cyanide' was therefore the name given to molecules containing a cyanide unit, even though very few of them are blue.

Cyanide is simply two atoms, one of carbon and one of nitrogen, bonded together as a unit (–CN) that forms part of a larger molecule. There are a staggering number of cyanide compounds, and they occur throughout the natural world as well as in synthetic versions. Their toxicity depends on the ease with which the bond between the cyanide unit and the rest of the molecule can be broken. For example, the bond between cyanide and a hydrogen atom in hydrogen cyanide (H–CN) is very easily broken, and the compound is therefore extremely toxic; 50–150mg can kill an adult. However, the same cyanide unit bonded to a methyl group to form methyl cyanide (CH
3
–CN) is much less toxic (by a factor of approximately 5,000)
³⁴
because the bond is more difficult to break. If accidentally ingested, most of the methyl cyanide would be excreted by the body long before the cyanide could be released.

Many plants contain cyanide compounds, but some are more dangerous than others. It depends on the type and amount of cyanide compound present. The seeds or pits of plants of the genus
Prunus
all contain cyanide; the stones or pips of peaches, cherries, apples and bitter almonds can be particularly dangerous and potentially lethal in large quantities. This is because the seeds contain cyanide in the form of a compound called amygdalin, which is readily metabolised by enzymes in the small intestine to release hydrogen cyanide.

Agatha Christie often refers to the scent of bitter almonds, to indicate that cyanide had been used. In fact, it's not that cyanide smells of bitter almonds; bitter almonds smell of cyanide.

Methods for distilling cyanide from natural sources have been known for thousands of years. One of the first references to poisoning dates from an ancient papyrus that refers to a
lethal punishment for speaking the name of God: ‘repeat not the name I.O.A. [i.e. ‘Jehovah'], under the penalty of the peach tree';
³⁵
indeed, in Agatha Christie's
Hallowe'en Party
the murderer commits suicide by drinking a liquid smelling of peaches. Laurel leaves are another natural source of cyanide that has been used since the time of the Romans, giving ‘Caesar's Laurel Crown' in William Blake's poem a particularly sinister symbolism.

Natural sources of cyanide have also been used in more recent times. In 1845 apple pips were used as a defence in the trial of John Tawell, who was accused of murdering his mistress Sarah Hart with cyanide.
³⁶
Tawell was known to have purchased prussic acid from a pharmacy some time before Hart died. Prussic acid was known to be a dangerous substance but Tawell claimed the prussic acid was for 'external application'. At the time there was a vogue for using solutions of prussic acid as a skin lotion. One commercial product, ‘Dr Eliotsom's Lotion of Prussic Acid', was recommended for moistening the skin before and after shaving. Lethal amounts of prussic acid can be absorbed through unbroken skin; shaving cuts and abrasions could only have eased the absorption. Thankfully the fashion
did not last. Tawell's purchase was added to a bottle of beer, which Sarah drank. A neighbour saw Tawell leave the house, and hearing Sarah's cries went to see if she was all right. She found Sarah writhing on the floor in agony, and frothing at the mouth. She died before the doctor arrived.

The police were alerted and raced after Tawell, but they couldn't stop him before he boarded a train for London. A telegraph message was sent to London describing him and instructing the police there to arrest him. It was the first time the telegraph system had been used in this way, and the case generated huge publicity because of it.

At Tawell's trial, the defence barrister, Sir Fitzroy Kelly, proposed that the cyanide that had killed Sarah had come from the pips of the apples she was so fond of eating. The lethal dose of apple pips is about 200g; Sarah would have had to eat thousands of apples to ingest enough pips, and they would also have had to be well chewed to release the poison. The jury were unimpressed, and he was found guilty. Tawell was executed for his crime and his barrister was known as ‘Apple-pips' Kelly for the rest of his career.

Bitter almonds and apricot kernels contain considerably more cyanide-containing amygdalin than apple pips; just a few apricot kernels can be deadly, but there is another plant that contains even more cyanide. Cassava is probably the most dangerous cyanide-containing plant regularly consumed by humans. It forms an important part of the diet of millions of people living in the tropics. Bitter cassava can contain 1g of cyanide in every kilogram of root, in the form of two compounds, linamarin and lotaustralin, which share a close similarity with amygdalin (all three are in the same class of compounds, the cyanogenic
³⁷
glucosides). Sweet cassava is a different variety that contains considerably less cyanide, but people tend to grow the bitter variety as it is more resistant to pests and, quite possibly, to thieves. Eating a few mouthfuls of
raw bitter cassava is unlikely to kill you straight away, but it will cause severe illness. Raw cassava must be processed to remove the cyanide by grinding the vegetable into flour and soaking it in water for anything between five hours and three days (variations depend on cassava variety and local tradition). The soaking process allows the enzyme luminase, which is also present in the vegetable, to convert the cyanogenic glucosides into hydrogen cyanide, which evaporates from the water. The amount of cyanide compounds in the root increases in droughts, and with less water available for the soaking process people are particularly vulnerable to the effects of the poison at these times. Failure to prepare cassava properly can lead to goitre and damage to the nervous system, manifesting itself as a condition known as
konzo
. Individuals with
konzo
have problems walking, and with coordination generally. The condition is irreversible, and can be fatal.

Eating very small quantities of cyanide poses no health risks: we have all swallowed the occasional apple pip with no adverse reaction, because the body has some immunity against cyanide compounds.
³⁸
Humans evolved on a diet featuring foraged plants, and we have adapted over thousands of generations to cope with a certain level of cyanide exposure. Almost every cell inside the body contains an enzyme called rhodanase that converts cyanide (–CN) into thiocyanate (–SCN). Thiocyanate is about a thousand times less toxic than cyanide, and it can be readily excreted in urine. Our bodies have the capacity to process around 1g of cyanide every 24 hours; problems occur when the system is overloaded by a sudden influx of large amounts.

One animal species, however, is completely immune to the effects of cyanide. The greater bamboo lemur has evolved a taste for the shoots of the Madagascan giant bamboo, and it eats almost nothing else. These shoots are laced with cyanide
compounds, but the lemur has evolved an immunity that allows it to feast away to its heart's content.