Saturday, August 20, 2011

Arsenic in Air, Hair and Water

On Saturday 20th August 2011, the Sydney Morning Herald reported that the chemical company Orica "discharged up to 1.2 megalitres of effluent containing traces of arsenic above its environmental protection licence cap yesterday afternoon".
Arsenic is toxic, it disrupts the transport of energy within cells and metabolism. The minimal lethal dose of arsenic in adults is about 1mg per kilogram of body mass per day, but arsenic trioxide is about 500 times more toxic than pure arsenic.

The Romans used arsenic compounds, especially naturally occurring arsenic sulfides, as medicines. The Roman writer Dioscorides (40-90) wrote in De Materia Medica (Medical Matters) that arsenic sulfides could be used to treat warts and skin eruptions, but warned that the remedy could cause the patient's hair to fall out! It is believed that Agrippina used arsenic trioxide to murder her husband so that she could marry her uncle, the Emporer Claudius.
At about the same time, the Chinese were using arsenic compounds to kill flies and rodents while Indians were using them to preserve paper from attack by insects.

In medieval Europe, arsenic trioxide was being used to treat malaria, while arsenic sulfides were used to treat arthritis, asthma, tuberculosis, and diabetes.

In 1809, Dr. Fowler's Solution first appeared in the London Pharmacopoeia, and it was considered to be a cure for almost everything! Fowler's solution was a mixture of potassium arsenite in lavender water. It was prepared by dissolving 10g of arsenic trioxide and 7.6g of potassium hydrogen carbonate in 1L of distilled water, then adding a little alcohol and lavender oil. The maximum single dose recommended was 0.5mL of Fowler's Solution which could be added to a glass of water or wine.

Arsenic was very common in European households up until the late 19th century.
Arsenic was being used to provide brilliant colours in dyes and paints:
  • yellow orpiment, As2S3 (a mineral in use since Ancient times)
  • red realgar, As4S4 (a mineral in use since Ancient times)
  • Scheele's Green, copper arsenite, CuHAsO3 (first produced in 1778)
  • Emerald Green, a combination of copper acetate and copper arsenite (first produced in 1822)
In the 19th century, arsenic-based green colours were being used to colour paint, wallpaper, soap, lampshades, children's toys, candles, soft furnishings, and even food. By the late 19th century, Gosio's disease, sickness resulting from breathing the air in rooms decorated with arsenic compounds, was identified. The deadly vapour was not identified as trimethylarsine until the 1930's.

Napoleon Bonaparte died on 6th May 1821 at Longwood House on Saint Helena. Samples of Napoleon's hair were analysed in 1995 and were found to contain between 33ppm and 17ppm of arsenic, the maximum "safe" limit is currently considered to be about 3ppm and the normal level is about 1ppm. While some people believe that Napoleon was deliberately poisoned,it is possible that green furnishings at Longwood House could be to blame for the high levels of arsenic in his body.

Arsenic has also been discovered in the hair of "mad" King George III of Great Britain who died in 1820. In 2003, samples of the King's hair found in the Science Museum London were analyzed and found to contain about 17ppm arsenic.

in 1904, Julius Nieuwland added an aluminium chloride catalyst to a mixture of acetylene and arsenic trichloride to produce an arsenic compound that came to be known as Lewisite. Unfortunately Nieuwland had taken no safety precautions so he breathed in some of the vapour, was taken ill and spent the next few days in hospital. During World War I, Winford Lewis heard about Nieuwland's earlier experiment, and he learnt how to produce the toxic compound under carefully controlled conditions so that it could be used as a weapon. By November 1918, the USA was shipping deadly Lewisite to Europe. Lewisite was then used by the Japenese against the Chinese in Manchuria in 1940, and by Saddam Hussein in the Iran-Iraq war in the 1980's.

Tube wells, drilled in the 1970's in West Bengal, India and Bangladesh, were installed in a drive by the United Nations Children's Fund (UNICEF) to provide safe drinking water for a population that had traditionally taken its water from contaminated streams, rivers, and ponds, and therefore suffered from water-borne diseases such as gastroenteritis, typhoid and cholera. By 1983 the population, more than 30 million people, were showing signs of arsenic poisoning. The water in many of the wells had arsenic levels of between 50ppb and 4000ppb. At the time, the World Health Organisation (WHO) stated that drinking water should not contain more than 10μg/L.

In the 20th century, copper arsenite, also known as Paris Green, and lead arsenate have been used as a horticultural spray to kill moths on apple trees, but these compounds have now been phased out. Chromium copper arsenate, used to treat wood to prevent it rotting and being eaten by termites, has been phased out in some countries like Australia, Canada and the USA, but is still being used in others. In the electronics industries, arsenic is added to silicon and germanium semiconductors to provide electrons to the crystal lattice. Gallium arsenide is a semi-conductor which has the ability to convert electric current to laser light, so this is a growing use for the world's arsenic.

Further Reading
Volume Conversions
Parts per Million Concentration
W/V %
Writing Ionic Formulae
Oxidation States (Numbers)

Study Questions:
  1. Convert 1.2 megalitres to a volume in
    • litres
    • kilolitres
    • gigalitres
    • millilitres
  2. "The minimal lethal dose of arsenic in adults is about 1mg per kilogram of body mass per day". Calculate the mass of the dose of arsenic that would be lethal in each case below:
    • 1 dose given in 1 day to a man weighing 90kg
    • 1 dose given in 1 day to a woman weighing 65kg
    • 1 dose given in 1 day to a child weighing 30kg
    • 1 dose given 3 times a day with meals to a person weighing 70kg.
  3. The arsenite ion has the formula AsO33- and the arsenate ion has the formula AsO43-.
    • Write the formula for potassium arsenite
    • Write the formula for potassium arsenate
    • Write the formula for calcium arsenite
    • Write the formula for barium arsenate
    • Write the formula for ammonium arsenate
    • Write the formula for copper (II) arsenite
    • Write the formula for lead (II) arsenate
  4. Give the oxidation state (number) of arsenic in each of the following:
    • AsO33-
    • AsO43-
    • As2S3
    • As4S4
    • HAsO32-
    • As2O3
    • AsCl3
  5. Calculate the concentration of arsenic ions in mol/L in 1L of Fowler's Solution using the recipe provided in the article (assume all the arsenic present is in the form of arsenic ions).
  6. For a 0.5mL dose of Fowler's Solution, calculate
    • the mass of arsenic present in grams
    • the mass of arsenic present in milligrams
    • the concentration of arsenic in parts per million
  7. Assuming 10g hair samples were tested for arsenic
    • What is the mass of arsenic present in a healthy persons hair if the normal level is 1ppm?
    • The safe limit for arsenic in hair is 3ppm, what mass of arsenic is this equivalent to ?
    • Napoleon's hair was found to contain between 17ppm and 33ppm arsenic. Convert each of these concentrations to a mass of arsenic.
  8. For the water tested in the Asian tube wells:
    • convert 4000ppb to a concentration in ppm
    • calculate the mass of arsenic in 1L of water if the concentration is 50ppb
    • convert the safe limit for arsenic in drinking water, 10μg/L, to a concentration in mol/L
    • calculate the mass of arsenic present in 1L of drinking water that contains 10μg/L arsenic


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