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Friday, 21 November 2014


An analgesic, or painkiller, is any member of the group of drugs used to achieve analgesia — relief from pain. The word analgesic derives from Greek ἀν-, "without", and ἄλγος, "pain.

There are two main types of painkiller - opioids and non-steroid anti-inflammatory drugs (or NSAIDs).  The type of medicines that you need to treat your pain depend on what type of pain you have.


Analgesic drugs act in various ways on the peripheral and central nervous systems. They are distinct from anesthetics, which reversibly eliminate sensation, and include paracetamol (known in the US as acetaminophen or simply APAP), the non-steroidal anti-inflammatory drugs (NSAIDs) such as the salicylates, and opioid drugs such as morphine and oxycodone.

The exact mechanism of action of paracetamol/acetaminophen is uncertain but appears to act centrally in the brain rather than peripherally in nerve endings. Aspirin and the other non-steroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenases, leading to a decrease in prostaglandin production. In contrast to paracetamol and the opioids, this reduces not only pain but inflammation as well.
The graphic below from Compound Interest takes a look at a selection of common painkillers, their common brand names, and how they work.

Click to enlarge

For pain associated with inflammation, such as back pain or headaches, paracetamol and anti-inflammatory painkillers work best.

If the pain is caused by sensitive or damaged nerves, as is the case with shingles or sciatica, it is usually treated with tablets that are also used for epilepsy and depression. These tablets change the way the central nervous system works.

The aim of taking medication is to improve your quality of life. All painkillers have potential side effects, so you need to weigh up the advantages of taking them against the disadvantages

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Friday, 14 November 2014


Platinum has the chemical symbol Pt and atomic number 78. It’s a dense, malleable, ductile, highly unreactive, precious, grey-white transition metal. Its name is derived from the Spanish term platina, which is literally translated into "little silver”.

Platinum occurs in the wild as the pure element as well as alloyed with iridium, known as platiniridium.  It is one of the rarest elements in the Earth's crust with an average abundance of approximately 5 μg/kg.

In addition to its high density, resistance to oxidation and other desirable qualities, platinum is remarkably chemically unreactive. For these reasons, a 90-10% alloy of platinum-iridium is still used as the International Prototype Kilogram. Originally, this prototype kilogram was made of pure platinum, but iridium was added to increase its hardness while retaining platinum's many desirable qualities.

Platinum Nuggets

Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewellery. Being a heavy metal, it leads to health issues upon exposure to its salts, but due to its corrosion resistance, it is not as toxic as some metals. Some compounds containing platinum are applied in chemotherapy against certain types of cancer.

Platinum;s resistance to wear and tarnish is well suited to its use in fine jewellery.

Platinum is obtained commercially as a by-product from nickel and copper mining and processing.  As an example, of the 245 tonnes of platinum sold in 2010, 113 tonnes were used for vehicle emissions control devices (46%), 76 tonnes for jewellery (31%). The remaining 35.5 tonnes went to various other minor applications, such as investment, electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.

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Friday, 7 November 2014

On this day - Marie Curie

Marie Curie was a Polish-born physicist and chemist and one of the most famous scientists of her time. Together with her husband Pierre, she was awarded the Nobel Prize in 1903, and she went on to win another in 1911.

Marie Sklodowska was born in Warsaw on 7 November 1867, the daughter of a teacher. In 1891, she went to Paris to study physics and mathematics at the Sorbonne where she met Pierre Curie, professor of the School of Physics. They were married in 1895.

She developed a theory of radioactivity (a term that she coined) and techniques for isolating radioactive isotopes.  She also discovered two elements, polonium and radium. Under her direction, the world's first studies were conducted into the treatment of neoplasms, using radioactive isotopes. She founded the Curie Institutes in Paris and in Warsaw, which remain major centres of medical research today.
During World War I, she established the first military field radiological centres.  After a quick study of radiology, anatomy, and automotive mechanics she procured X-ray equipment, vehicles, auxiliary generators, and developed mobile radiography units, which came to be popularly known as petites Curies ("Little Curies").  She became the director of the Red Cross Radiology Service and set up France's first military radiology centre, operational by late 1914.
Marie and her husband worked together investigating radioactivity, building on the work of the German physicist Roentgen and the French physicist Becquerel. In July 1898, the Curies announced the discovery of a new chemical element, polonium. At the end of the year, they announced the discovery of another, radium. The Curies, along with Becquerel, were awarded the Nobel Prize for Physics in 1903.

Marie received a second Nobel Prize, for Chemistry, in 1911.

Curie died in 1934 due to aplastic anaemia brought on by exposure to radiation – including carrying test tubes of radium in her pockets during research (she also stored them in her desk drawer, remarking on the faint light that the substances gave off in the dark) and her World War I service in mobile X-ray units created by her.  She was exposed to X-rays from unshielded equipment.

Marie and Pierre Curie experimenting with radium, a drawing by André Castaigne

Because of their levels of radioactivity, her papers from the 1890s are considered too dangerous to handle.  Even her cookbook is highly radioactive.  Her papers are kept in lead-lined boxes, and those who wish to consult them must wear protective clothing.

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Friday, 31 October 2014

Autumn leaves - the chemistry behind the colour

As Autumn pushes onwards the leaves on the trees have lost their green colour and have allowed the vibrant hues of autumn to show through. Although this change may initially seem a simple one, the vivid colours are a result of a range of chemical compounds.

A green leaf is green because of the presence of a pigment known as chlorophyll, which is inside an organelle called a chloroplast. When they are abundant in the leaf's cells, as they are during the growing season, the chlorophylls' green colour dominates and masks out the colours of any other pigments that may be present in the leaf. Thus the leaves of summer are characteristically green.

As summer fades, so too does the amount of light, and thus chlorophyll production slows  The existing chlorophyll decomposes. As a result of this, other compounds present in the leaves can come to the fore, and affect the perceived colouration as shown in the infographic below featured on the CompoundInterest website.  Click on the link below for a larger picture.

Autumn Leaves-click to enlarge
Carotenoids are present in leaves the whole year round, but their orange-yellow colours are usually masked by green chlorophyll.  Carotenoids provide colourations of yellow, brown, orange, and the many hues in between.

The reds, the purples, and their blended combinations that decorate autumn foliage come from another group of pigments in the cells called anthocyanins. Unlike the carotenoids, these pigments are not present in the leaf throughout the growing season, but are actively produced towards the end of summer.   They develop in late summer in the sap of the cells of the leaf, and this development is the result of complex interactions of many influences — both inside and outside the plant. Their formation depends on the breakdown of sugars in the presence of bright light as the level of phosphate in the leaf is reduced.

The brown colour of leaves is not the result of a pigment, but rather cell walls, which may be evident when no colouring pigment is visible.

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Friday, 24 October 2014

On this day...

After the end of World War II on October 24, 1946 and a good while before the Sputnik satellite opened the space age, a group of soldiers and scientists in the New Mexico desert saw something new and wonderful—the first pictures of Earth as seen from space.

The White Sands rocket (official name V-2 No. 13) was the first man-made object to take a photograph of the Earth from outer space.   Launched from the White Sands Missile Range in White Sands, New Mexico, the rocket reached a maximum altitude of 107.5 miles (173 km), well above the commonly accepted boundary of space at 100 kilometres.

The famous photograph was taken from an altitude of 65 miles (104 km) with an attached 35 mm black-and-white camera.

Snapping a new frame every second and a half, the rocket-borne camera climbed straight up, then fell back to Earth minutes later, slamming into the ground at 500 feet per second. The camera itself was smashed, but the film, protected in a steel cassette, was unharmed.

It was one of many firsts for the V-2 research program of the late 1940s, during which the Army fired dozens of captured German missiles brought to White Sands in 300 railroad cars at the end of the war. While the missileers used the V-2s to refine their own rocket designs, scientists were invited to pack instruments inside the nosecone to study temperatures, pressures, magnetic fields and other physical characteristics of the unexplored upper atmosphere.

Earth from Space in colour

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Friday, 17 October 2014

pH Indicators

A pH indicator is a colour changing (or halochromic) chemical compound that is added in small amounts to a solution so that the pH (acidity or basicity) of the solution can be determined visually.
A pH indicator is a chemical detector for hydronium ions (H3O+) or hydrogen ions (H+).  Normally, the indicator causes the colour of the solution to change depending on the pH.

pH (potential of hydrogen) is a scale of acidity from 0 to 14. It tells how acidic or alkaline a substance is. More acidic solutions have lower pH. More alkaline solutions have higher pH. Substances which are not acidic or alkaline (neutral) usually have a pH of 7. Acids have a pH less than 7. Alkalis have a pH greater than 7.

pH indicator solutions are themselves weak acids or bases.  As one chemical is added it changes the arrangement of the electrons in the molecule causing it to absorb different wavelengths of light and therefore appear different in colour.

Different chemicals can be used for different pH ranges as shown in the diagram below.
pH indicators are frequently employed in titrations in analytical chemistry and biology to determine the extent of a chemical reaction. Because of the subjective choice (determination) of colour, pH indicators are susceptible to imprecise readings. For applications requiring precise measurement of pH, a pH meter is frequently used.
Many plants or plant parts contain chemicals from the naturally-coloured anthocyanin family of compounds. They are red in acidic solutions and blue in basic. Anthocyanins can be extracted with water or other solvents from a multitude of coloured plants or plant parts, including from leaves (red cabbage); flowers (geranium, poppy, or rose petals); berries (blueberries, blackcurrant); and stems (rhubarb). Extracting anthocyanins from household plants, especially red cabbage, to form a crude pH indicator is a popular introductory chemistry demonstration.
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