I would like to tell you about phosphorus, my favourite element in the periodic table. Phosphorus is an excellent candidate for a poison blog as there are a surprising number of ways it can kill you. It is also the most appropriate element for a Hallowe’en blog as it is easily the spookiest member of the periodic table and associated with stories of alchemists, glowing skulls, graveyard ghosts and spontaneous human combustion.

Phosphorus is an essential part of life. When combined with oxygen to make phosphates, it holds our DNA together, makes our bones strong and carries out fundamental chemical reactions within our cells. But phosphorus also has its dark side. Some have described it as “the Devil’s element”.

Pure phosphorus comes in a variety of different forms, differentiated by colours produced by the different ways the atoms can be arranged. There is white phosphorus (also described as yellow), red, violet, black – and most recently pink has been added to the list. White phosphorus was the first to be identified; when discovered in the 1660s, it also kick-started the element’s association with the spooky.

The discovery was made by the alchemist Hennig Brandt who was boiling his own urine in search of gold (I kid you not). After days of heating up litres of stagnant pee, Hennig managed to isolate a white, waxy solid, which was probably something of a disappointment after his long and olfactorily-challenging work. But his mood must have perked up when it got dark and he observed that this newly-created substance glowed with an eerie green light.

Hennig named the new substance phosphorus, after the Greek for “light bearer”. At a time when light was usually produced by burning something, Hennig’s discovery was source of great curiosity, and it was hoped that phosphorus might offer a safer alternative to candles for lighting the home. There are two problems with this. Firstly, phosphorus compounds stink like you wouldn’t believe (trust me on this one) and no one would want the stuff in their home when it can degrade over time to produce some truly fetid odours.

The second problem is the flammability of white phosphorus. The cool, greenish glow of phosphorus is caused by its reaction with oxygen, but it doesn’t take much for this reaction to accelerate and develop into a fire, as the 17th century chemist Nicolas Lemery found out: “After some experiments made one day at my house upon the phosphorus, a little piece of it being left negligently upon the table in my chamber, the maid making the bed took it up in the bedclothes she had put on the table, not seeing the little piece. The person who lay afterwards in the bed, waking at night and feeling more than ordinary heat, perceived that the coverlet was on fire.” Lemery’s guest was lucky to survive: phosphorus burns with an incredible intensity and produces thick, choking white smoke (it is for this reason that white phosphorus has been used in incendiary bombs and to produce smoke screens).

The ease with which phosphorus and some of its compounds will catch fire has led to suggestions that it might be the cause of spontaneous human combustion. Microbes have been found to be able to convert ordinary phosphates in food into highly reactive phosphine chemicals that can spontaneously combust when exposed to the air. The highly flammable phosphorus-based compounds have been found in human and animal faeces, but in tiny quantities. Although this is a theoretically possible explanation for spontaneous human combustion it is extremely unlikely to be true. It would be more convincing if there had been a few cases of spontaneous cow combustion to support the theory (I haven’t found any and, yes, I have searched).

However, similar processes might explain how belches of phosphorus gases from decomposing remains in graveyards could produce strange glowing vapours that have be mistaken for graveyard ghosts or will-o’-the-wisps.

The problems of flammability sank any hope of using white phosphorus for indoor lighting but it opened up another possibility: matches. Using white phosphorus for match heads meant that a flame could be produced with only the slightest heat from friction. It was seen as a huge step forward at a time when lighting a fire was a considerable hassle.

Phosphorus-laden strike-anywhere matches were produced in the nineteenth century by the billion. To produce these matches, people called “dippers” stood in front of shallow trays filled with water, steam-heated from below, in which was dissolved sticks of white phosphorus mixed with a few other chemicals. Racks of sticks twice the length of a matchstick when then dipped either side and allowed to dry before the sticks were chopped in half. The resulting matches were then boxed up ready to be sold.

Dippers worked 14-hour days and poorly-ventilated factories mean they would have been breathing in phosphorus fumes the whole time. Others who mixed the chemicals as well as those who boxed up the matches were also exposed to high levels of phosphorus. The result was that phosphorus would start to infiltrate the body. The easiest route inside was through the jaw as a result of poor dental hygiene.

Symptoms would start off with tooth ache, then the teeth would fall out. The face would swell up and abscesses along the jaw would ooze the most foul-smelling pus. Holes would open up in the face along the jaw line, through which could be seen the dead bone underneath. Sometimes the bone glowed in the dark from the accumulated phosphorus. The only remedy was to remove the individual from exposure to phosphorus – but this wasn’t really an option, as they would lose their income. Instead, to prevent phosphorus from moving to the internal organs and killing the individual through liver damage, the affected jawbone was removed.

You can see the devastating effects of what became known as phossy jaw in anatomical collections such as the one at Barts Pathology Museum. The medical case on display on the ground floor of this spectacular three-storey medical collection shows the jawbone of one such sufferer, removed to save the patient from the potentially terminal effects of exposure. It is easy to see where the bone has been eaten away by the phosphorus the patient must have been breathing in for years.

The patient stayed in hospital for six weeks to recover and grow a new jawbone before he was released. Sadly, after what must have been a truly horrendous experience, the patient died the very night he returned to his home. It is thought he choked in his sleep.

Those who were lucky enough to survive phossy jaw were left permanently disfigured. You can understand why match workers went on strike. Though the first cases of phossy jaw presented themselves in the 1850s, white phosphorus continued to be used until the early 20th century. In 1910, Britain finally banned the use of white phosphorus in matches and it was replaced with the much safer red phosphorus that still adorns the side of match-boxes.

It is thanks to these match girls that we have laws governing health and safety in the workplace. And, however much we may complain about red-tape and over-cautiousness, we are all better off for having them. Because of health and safety legislation any glowing skulls you encounter over Hallowe’en will be covered with non-toxic paints that glow because of the effects of light rather than chemical reactions. Any graveyard ghosts you meet, however, might be due to phosphorus, or, perhaps, something else entirely …