Iodine – I – With Silver makes photos, rain and snow

Iodine (I – Atomic Number 53) has very strong photography connections – and was used in some of the earlier photosensitive solutions as AgI – silver iodide – in daguerreotypes, named after Louis Daguerre.  More recently film emulsions have tended to be mostly AgCl and AgBr – Silver Chloride and Silver Bromide, but usually the Silver Bromide crystals have a small amount of Silver Iodide present to improve the light sensitivity characteristics.  Iodine is also found in seaweed, including Kelp – my first Iodine picture.

Kelp
Kelp

The discovery of Iodine related to seaweed too.  Bernard Courtois was using ash from seaweed as a source of Potassium for creating saltpeter (Potassium Nitrate) and one day noticed purple fumes when he added sulphuric acid to the ash.  The fumes condensed to form crystals and he guessed this was a new element – the name Iodine being given from the Greek ‘iodes’ meaning violet.  Iodine sublimes (goes right from a solid to vapour) at room temperature – so easy enough to sort of re-create this discovery.

Clouds over Amsterdam
Clouds over Amsterdam

Another use for Silver Iodide cystals is to seed clouds.  I’m pretty sure these clouds were not seeded though – I’m sure Amsterdam, much like Seattle – does not need any more clouds than they normally get!  As well as seeding clouds, Silver Iodide crystals are used in snow machines where a combination of high pressure air is used to reduce thelocal temperature – and then a jets of water and AgI crystals are sprayed together to give the ice crystals a head start.

Iodine Is very important to health and we need a daily intake of around 0.1 milligrams.  Most of the bodies 20 milligrams is found in the thyroid gland.  Radioactive Iodine (I 131) can accumulate in the thyroid – which can be used for good to fight cancer – but I the exposure is more sinister then normal Iodine can be taken (as Potassium Iodide) to replace the radioactive Iodine.  Potassium Iodide is also added to  table salt to help avoid Iodine deficiency.

The main source of Iodine is from the sea – not so much from seaweed these days – but from brine.

Next up is Cerium – Ce – Named for the asteroid Ceres!

More kelp
More kelp

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Aluminium – Al – You say Aluminum and I say Aluminium

Aluminium Foil
Aluminium Foil

Aluminium (Al – Atomic Number 13). Or should I say Aluminum? Officially (IUPAC – The International Union of Pure and Applied Chemistry) say the former, and that’s the one I’m most used to – but in the United States Aluminum is the more common. IUPAC also accept this as a variant. The history of the name gets even more interesting, as it is this latter spelling that was first given by Humphry Davy in 1812 when he was working to isolate the metal from alumina (after he’d dismissed the name of Alumium).

Aluminium is the third most abundant element on earth, following Oxygen and Silicon – but is quite reactive so is rarely found as a native metal. The chief ore of Aluminium is bauxite – and I even remember from school geography that Australia and Brazil are the main producers – with cheap electricity being key to extraction. One thing I didn’t know – 5% of the electricity generated in the United States is consumed by Aluminium production!

Float Plane - Kenmore Air
Float Plane – Kenmore Air

Aluminium is light and resists corrosion (protected by a layer of Aluminium Oxide that forms when Oxygen from the air reacts with the surface or pure Aluminium, and these p[roperties make it perfect for use in the aerospace and other transportation industries – sometime on its own, but also as alloys which can increase its strength.  Another important use is for transmission of electivity – power lines benefit from the greater per weight conductivity compared to copper.  Aluminium foil and other forms of food packaging are more common uses of Aluminium – and an historically significant use was for the capstone for the Washington Monument.

Power lines
Power lines

Next up – Iodine!

Magnesium – Mg – Atomic Number – 12! #GoSeahawks

NYE Space Needle, Seattle
Magnesium - Atomic Number 12
Magnesium – Atomic Number 12

What better element for Super Bowl week on my Periodic Table of Photography than Magnesium (Mg – Atomic Number 12). Go Seahawks!

Magnesium is at the other end of the density scale from the last element I featured – Tungsten – and is only 2/3 the density of Aluminium.  Alloys of Magnesium and Aluminium are used where weight (or lack of it) are important.  Cars, planes, luggage, laptop shells and also camera bodies.  So a key modern photography use – as well as a very old photography use – flash powder – as it ignites easily in air and burns with a very bright light.  Later, flash bulbs, or the flash cubes on Kodak Instamatics used Magnesium ribbon – ignited by an electrical charge. This property also led to its use in flares, sparklers and other fireworks.

This was New Years Eve a couple of years ago – but hopefully the fireworks will be loud this Sunday too!

NYE - Space Needle
NYE – Space Needle

Magnesium is also a very important element biologically, being the seventh most abundant element by mass in the body and integral to the working of many human enzymes.  In plants it is at the heart of chlorophyll – critical to photosynthesis and which leads to Oxygen production in green plants.

Magnesium is found in minerals such as magnesite and dolomite, but industrial production makes use of its abundance in sea water.  It was named after a district in Greece – Magnesia – where is was found along with similarly named Magnetite (an iron oxide) and Manganese (an element – Mn).

Magnesium Alloy wheels
Magnesium Alloy wheels

An experiment that I always remember from school was the thermite experiment – where Magnesium ribbon is used as a fuse to start the exothermic reaction of a mixture of an oxide and a metal – usually in chemistry lessons Iron Oxide and Aluminium – which then produces molten Iron and Aluminium Oxide. In our class this was done in a clay flower pot and the molten Iron stream out of the bottom…

Mag wheels became a common term for lightweight alloy wheels on cars – and these may or may not really be Magnesium or a Magnesium alloy – but the name stuck.

Epsom salts (hydrated Magnesium Sulphate) were originally discovered by a farmer in Epsom, England in 1618 – who noticed that his cows would not drink water from a particular well as it had a bitter taste.  The farmer noticed however that the water helped scratches and rashes to heal – and its fame spread. Another medicinal use of Magnesium salts is as an antacid (Magnesium Hydroxide) – such as Milk of Magnesia.

Following Magnesium I have another light weight metal – as I spell out AlIce – with Aluminium, Iodine and Cerium.

NYE Space Needle, Seattle
NYE Space Needle, Seattle

Tungsten – W – Who says heavy metal is boring?

Seattle - SR-99 near the Washington State Ferry Terminal

Tungsten (W – Atomic number 74) is one of the densest metals, 1.7 times heavier than lead, and up there with gold and uranium.  It has a very high melting point – 3413 °C – and is also alloyed with other metals to strengthen them.

Drill bit
Drill bit

These properties account for the major uses of tungsten, one which is dying out – the use as a filament in incandescent lamps (compact fluorescent and LED are much more efficient means of creating more light and less heat) and the other of creating very hard materials that withstand high temperatures.  Arc-welding and heating elements in furnaces, as well as drill tips are an example of these uses.  Tungsten Carbides (W2C and WC) are formed when powdered tungsten is heated with carbon – and these carbides are very hard – used for machining tools as well as armaments.

Torch light bulb
Torch light bulb

Tungsten is also known as Wolfram is some languages (where the W comes from…).  The ores it is produced from are wolframite and scheelite.  Tungsten comes from the Swedish tung sten meaning heavy stone.

Like Tin, Tungsten is known as a conflict mineral due to the unethical mining practices that have been observed in the Democratic Republic of the Congo.  Industrial users of Tungsten need to be able to trace the supply chain to source.

Talking of sources, the 4th richest deposits of Tungsten can be found in the UK, in Devon, and the increasing world price has seen the recent work to re-open the mines, at Hemerdon, Dartmoor.  This work will also see Tin mining return to Devon as this metal is also found in the same deposits.

Drill bit
Drill bit

Tungsten’s discovery is credited to Juan and Fausto Elhuyar who isolated the metal in 1783, although earlier work on identifying a new metal from the minerals goes to Peter Woulfe and Wilhelm Scheele.  Even earlier (more than 350 years ago) a Tungsten based pigment had been used in China for a unique peach colour in porcelain.

Other uses of Tungsten are for ballast due to its density – both for ocean and space going ships, as well as racing cars -and it is also used in Jewelery and making darts (why isn’t darts an Olympic sport yet?)

Tungsten is also the heaviest element known to have a biological function (next heaviest is Iodine – 53) – and is found in some bacteria in an enzyme that typically reduces carboxylic acids to aldehydes.  Tungsten is the only element ever to have been the subject of patent proceedings – and General Electric’s 1928 attempt was rejected – and the 1913  U.S. Patent1,082,933 overturned.

I struggled to find good photographic uses of Tungsten, (Industrial X-ray equipment maybe – or ballast to keep tripods steady) so finishing with a picture that shows Seattle’s Highway SR-99 – which is being replaced by a tunnel – being dug by ‘Bertha‘ whose teeth may use Tungsten.  The teeth on this largest ever tunnel boring machine are interchangeable depending on the rock/soil mix being tunneled – perhaps if ‘Bertha’ had her Tungsten Carbine teeth in that steel pipe would not have stopped her…

Seattle - SR-99 near the Washington State Ferry Terminal
Seattle – SR-99 near the Washington State Ferry Terminal

Oxygen – O – Lifegiver

Oxygen (O – Atomic number 8) is certainly something we couldn’t live without – or in fact couldn’t live at all if the concentrations in the atmosphere were much more or less.  But I guess if the levels had fluctuated more or been different then we wouldn’t have evolved quite the way we did. 

Rust - Ferrous Oxide
Rust – Ferrous Oxide

I found it much easier to concentrate on what Oxygen does to things as subjects for my photographs – is consumed when things burn – oxidises things, such as creating rust on iron, and is given off by the process of photosynthesis – from plants both in and under oceans – though not too deep as the process also requires light.

Plants and oceans - keeping the amount of oxygen in the atmosphere just right
Plants and oceans – keeping the amount of oxygen in the atmosphere just right

Industrially Oxygen is produced mostly by fractional distillation of liquefied air, with some being produced by passing over molecular sieves which absorb the nitrogen.  Main uses are the production of steel, and in the chemical industry for production of materials going into plastics and fabrics.  And of course life support.  Hospitals, divers, submariners and spacemen.  Oxygen is not used for blowing up the bags that fall at you in airplanes – but the oxygen is still flowing…

It always seems strange talking about discovering something that was there all the time (like America for example) but understanding the components of air and isolating the individual elements I think is a tangible discovery.  Two people are credited with Oxygen’s discovery – the Swede Carl Wilhelm Scheele (first) and England’s Joseph Priestley (first to publish) – although Antoine Lavoisier (and his wife) had a big part too in understanding what they had found.  

The isotopes of Oxygen – atomic weight 16, 17 and 18 – and their relative abundance and the fact that water containing these isotopes evaporates at different rates – which is also temperature dependant has helped with both dating and identifying temperature fluctuations in the past – by analysis of ice cores.

Natural gas - needs oxygen to burn
Natural gas – needs oxygen to burn

Tin – Sn – Putting the reversal into reversal film

Tin (Sn – Atomic number 50) is a metal, except when it isn’t.  White Tin, or β Tin is a metal, but there is also another allotrope – α Tin – grey Tin which has no metallic properties at all.  This semi-conductor is stable under 13.2 °C, and can form from white Tin in a process known as Tin pest.  The most common uses of (white) Tin are as a component of solder and for coating steel to prevent corrosion – one example of which is to make ‘tins’ – or cans if you prefer. Solder was made from Tin and Lead – but other alloys with Tin are now used to avoid the toxic Lead.  Tin pest is more of a problem in Lead -free solder and can lead to joint integrity issues.  If you are not familiar with allotropes – carbon as diamond or graphite is a more common example.

Solder - which contains Tin
Solder joints on a circuit board on a hard drive

The previous posting was about Yttrium – which had just one stable isotope – and in contrast Tin has 10 – due to it having a magic number of protons.  Tin has been used since around 3000 BC and its addition to copper to form alloys like bronze heralded in a new age.  Tin mines in Devon and Cornwall operated from around 2150 BC – with the last one closing as recently as 1998.  This made the region one of the earliest parts of Britain to trade with the rest of Europe and even the Middle East –  both before and after the Roman invasion.

Tin lid
Tin lid

The main mineral that has always been the primary source of Tin is cassiterite, and this is now classified as a conflict mineral due to the conflict waged over control of the land where large deposits are fund – such as in the eastern parts of the Democratic Republic of the Congo.  Companies in the United States that use materials that come from conflict minerals need to be able to audit their supply chains to prove the origins – following the 2010 Dodd-Frank Wall Street Reform and Consumer Protection Act.

Now for the photography connection – and Tin(II) Chloride – SnCl2 – otherwise known as stannous chloride – is used in the ‘E-6’ photographic process for producing colour transparancies, or slides.  When I worked in a photo research lab the E-6 reversal bath was one of the formulations I worked on.  Stannous chloride is a reducing agent, and in the reversal bath it performs the same role that light does in exposing the silver halides that remains after the ‘First Developer’ has produced basically a black and white negative.  In print photography you take a negative – shine light through onto paper and then develop – for slides this all happens in the same piece of film.

Tin lid
Tin lid

The reversal bath prepares the reversed image by ‘exposing’ all the silver halide that has not been developed to a silver image in the first developer (which is a black and white developer)   and this silver halide can then be developed in the colour developer to product the positive image. The colour actually comes from dyes in the film reacting with the local oxidized developer in three layers sensitive to different parts of the spectrum.   A good article that show this effect weel is the Kodak one – Processing Solutions and their Effects.  The E-6 process applies to Kodak’s Ektachrome and Fuji’s Fujichrome and others – but probably the most famous transparency film – Kodachrome – goes through a slightly different process.  It has no dyes in the film (so the film can actually be thinner) but instead after first development it goes through a series of exposures to different coloured light and development in three different colour developers that contain the dyes – so building up the colour image without chemical reversal.  E-6 is a process you can do at home without too much difficulty – Kodachrome K-14 was much more involved – and I say ‘was’ as production of Kodachrome film ceased in 2009 and the last roles were processed in December 2010.

Next up in my photographic journey through the Periodic Table is Oxygen – and I might need to get a bit creative with a photo depicting O2.

Circuit board with solder joints
Circuit board with solder joints

Yttrium – Y – Clear white light

Yttrium (Y – Atomic number 39) is another transition metals (like Iron) and was named after the town in Sweden, Ytterby, where the mineral (Ytterbite) in which it was first found was picked up from a quarry. Today Yttrium has a number of uses – as its oxide it is added to glass for camera lenses to improve heat and shock resistance.  We have all starred at it as it was used for making phosphors, such as the red ones in used in televisions (non flat screen), and it is a regular additive to magnesium and aluminium alloys to improve strength  – and probably its most important current use is in the production of white LEDs. So a couple of photography related uses.

White LED from my Christmas lights
White LED from my Christmas lights

I must get a better lens for macros… Yttrium is fairly common – the 28th most abundant element in the earths crust, found in soil and sea water – and strangely found in cabbage (not enough to worry about though).  It is very similar to the lanthanides, its close neighbours in the periodic table, and mostly obtained from the same rare earth minerals.

Camera lens with periodic table reflection
Camera lens with periodic table reflection

The way it is used in white LEDs is interesting, as Cesium doped Yttrium Aluminium Garnet (YAG, Y3Al5O12) – it is a phosphor that emits a yellow light.  As a coating in high brightness blue InGaN diodes this converts some of the blue light to yellow – giving an overall white light.  The spectrum coverage is not perfect though – so even though it appears white the colour rendering isn’t ideal.  It is a fascinating (to me anyway) topic colour rendering – and has always been a challenge for colour photography to get an accurate representation of scenes that match to the way our eyes interpret them.  The colour can be affected very much by the light source – and it the white light doesn’t cover the full visibile spectrum then some colours just won’t look as expected – and this can be further challenged by the viewing conditions.  More over at Wikipedia – and the book The Reproduction of Colour gives lots more detail for those interested.

On final fun fact – and I’m sure gas mantles are something that few will remember – but these were used for propane lanterns (I remember them from caravan holidays) and where often used in the science lab as a demonstration of Geiger counters – as they used to be made with thorium which is radioactive.  Yttrium has replaced thorium now, so I guess science teachers bought up the old stock to keep the demonstrations going!

That finishes my first word – Fe Br U Ar Y – so next up come Tin, Oxygen and Tungsten – one life giver between two metals often connected with war and conflict – and the word is Sn O W.

Camera Lens