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Australian chemistry vacation

28 November 2011 - Leisure mode

You cannot blame a chemist for taking an interest in chemistry even when on vacation. So here is what your bloggist has to report on his recent three week stay in the Sydney - Melbourne - Hamilton triangle.
Sydney's two icons are the Sydney Harbour Bridge - 50,000 tonnes of steel - and Sydney Opera House - 26,000 tonnes of concrete. This blog admired the bridge but was having doubts on the opera house. Should not design follow function? The roof starts at eye level so it is easy to inspect the white ceramic tiles. The interior when entering the building is not decorated at all - just plain concrete. The tiles must have been a desperate solution by desperate engineers. As a building concept this homage to concrete certainly never caught on.

Australia is of course all about mining. The newspapers all agree that the country will get very rich from this industry in the coming years and the only thing that needs to be settled is how to tax and how to divide the earnings. Even selling uranium to India is no longer an issue. A new technology for gas exploration making headlines is fracking.
Evidence of past industries can be found in the blue mountains. Katoomba is now a focal point for hiking but remnants of coal mining can still be found. Even further away Hill end was a booming gold town in the 1870's and today an open-air museum. The local museum has a large display on the chemistry involved ranging from gold assaying to manufacturing explosives (nitric acid for on-site gelignite production).
The "Bald hill mine" never produced an ounce of gold. In 1872 an 80 meter shaft was dug to expose three layers of quartz. These layers are oriented perpendicular to the shaft and are hundreds of meters wide but only centimeters in thickness. Gold would then be present in the shape of flakes but gold never materialized. After this disappointment someone suggested that further down the mountain surely there had to be diamonds to be found. After laboring for another year excavating an airshaft and another 200 meters of mine tunnel the stage was set for disappointment number two.

The city of Melbourne is another gold-rush town but whereas the population of Hill End over the years dwindled to just 166, Melbourne now hosts over 4 million people. The city does not do iconic buildings like Sydney but makes up for it with a post-modern city center and an even post-post modern Yarra river southbank district. The city has electric trams and a public bike scheme so the environmental awards should be flooding in.
The nearest icon would probably be the Twelve Apostles site on the Great Ocean Road which are big blocks of rock in the surf pretending to guard the coast. In terms of material science the choice for limestone is unfortunate because the waves tend to eat it away but on the other hand as one apostle collapses after the other, new apostles are in the making.

The lake Taupo region in New Zealand is a volcanic hotspot. The NNNS geological museum (founded 1975) now boasts pieces of pumice and granite picked up during the Tongariri Alpine Crossing.
Water is the color blue? Boring! The emerald lakes on top of Mount Tongariro appear green due to leached minerals from thermal activity. Further downstream the water passing the Huka falls (from lake Taupo into the Waikato river) too has an unusual color, this time attributed to dissolved air. The Inferno Crater in the Waimangu Volcanic Rift Valley is part of a large hydrothermal system and the color of the water depends on the water level which changes periodically. The color is a bright blue when the water level is high due to a combination of suspended silica particles and turbulence. The iodine pool on the same site is only so-called because the mineral deposits have an ugly brown color.
The masters of chemistry in the Taupo area must be the glowworms (Arachnocampa luminosa) lurking in the Waitomo Caves. Suspended from the ceiling they attract insects looking for a way out of the cave by luciferine -based biolumiscence and trap them with a silk thread. The wikipedia article mentions that the illusion created is that of a starry sky at night. This blog disagrees: the ceiling looks more like a blue sky behind a forest canopy. In some way the distribution of the glowworms on the ceiling has relevance. It makes good sense that photography is not allowed inside the cave so if you want to find out for yourself you have to go there.




More bad news for Martians

05 November 2011 - Astrochemistry

In 2008 the Phoenix Mars Lander took all the fun out of astrobiology by finding a lot of perchlorate salts in Martian soil samples. It is reasoned that perchlorate compounds are too toxic to accommodate any life form. All that is left is finding out how the perchlorate gets there in the first place: It is very reactive and the two obvious precursors to perchlorate, ozone and chloride, are very scarce. Schuttlefield et al. took up the challenge and offer a new theory in a recent JACS publication (DOI).

They argue that due to the thin Martian atmosphere, UV radiation is more efficient and perchlorates can form by heterogeneous photocatalysis at a mineral surface. But what mineral? In one experiment rutile and anatase were compared. Both are silicon oxide semiconductors and well known to photocatalysis: radiation pushes out an electron (leaving a hole) which then lends a helping hand in any redox reaction. In the present case that would be chlorine oxidation with water forming a perchlorate ion and reduction of oxygen to water. The nett reaction is one highly endothermic between the chlorine ion and 2 equivalents of oxygen to one equivalent of perchlorate.

Schuttlefield notes the theory has drawbacks. For one it relies on the presence of liquid water but as it happens perchlorates do a great job in freezing-point depression. It is also true that water may be scarce in the present but more liquid water could have been available in the Martian past. Another drawback is the lack of evidence of any silicon oxide mineral on Mars but other semiconducting minerals could fit the bill.

The copper-platinum-bromine bullet

03 November 2011 - Making It Move VII

The copper platinum bromine bullet  The copper-platinum-bromine bullet is a new entry in our Making-It-Move competition, see Part VI here and brought to you by Liu & Sen of The Pennsylvania State University (DOI). The bullet is a 500 micron copper nanorod with a platinum tail produced from a known alumina template material. The technology behind this template is of interest by itself. Solid aluminum is anodized which means that the formation of the oxidized outer layer (alumina Al2O3) is accelerated. By selection of just the right solution a nanopothole array forms on the outer layer by a process of dissolution. A second anodization step deepens these holes which can then be used as a template.

The bullet was (400 micron length, half a micron diameter) constructed from the alumina template by first a copper sputtering process. Then copper as copper sulfate was electrodeposited filling the holes to a certain depth. In step two palladium as palladium chloride was also electrodeposited, the copper outer layer was then etched away (ammonium persulfate) and finally the alumina matrix was removed by a sodium hydroxide solution releasing the bullets!

When submerged into a bromine pool the bullets propel themselves forward powered by self-electrophoresis. One equation in the redox reaction responsible is oxidation of copper to the copper ion. The other equations are reaction of bromine with water to hypobromous acid (HBrO) and HBrO reduction to the bromine ion and again water. With hydrogen ions moving from the copper part to the platinum part and the bromine ions traveling in the opposite direction the nett bullet movement is caused by electro-osmosis. The top speed is 7 micron per second with the copper fuel spent within a minute.

Watch the movie (also in supporting info) for some dramatic footage of purple specs floating around in a purple square.




1665 chemistry update

01 November 2011 - Open access

philtransdjvu.jpgThe Royal Society last week announced the journal Philosophical Transactions of the Royal Society from now on is open access for the volumes published between 1665 and 1941 (Link). That is good news for those who think charging money by publishers for scientific articles more recent than 6 months is reasonable, charging money for older articles is questionable and charging money for one hundred year old publications is downright greed (articles priced on average between 20 and 40 dollars per article).
The odd thing about the announcement is that copies of the transactions are all over internet including wikimedia commons here so where exactly is the novelty? In any case it has been a joy to be able to read the chemistry contributions from that issue 1 from the year 1665.

Take for example the account by Robert Moray (one of the Chemical Society founding fathers) on page 45 on the Mineral of Liege (look a 365 year old DOI! => DOI, Huh?, no wait). In it he describes the (industrial?) production of brimstone and vitriol from said mineral by breaking it in little pieces and applying lot of heat. The process starts to make sense if the mineral is pyrite (FeS2), the city is Liege, brimstone is sulfur and vitriol iron sulfate and/or sulfuric acid. When the sulfur is extracted the residue is collected and soaked in water until an egge will fwim upon the liquor. Then more boiling takes place and then the copperas (used as an ink) will separate out as pyrite's oxidation product leaving aqueous sulfuric acid behind.

On page 10 of the same issue Society co-founder and scientist Robert Boyle (Boyle's law) completely wasts his colleagues time (and countless scientists would follow his example) by reporting on a Very Odd Monstrous Calf (DOI). On a more serious note Boyle also reports on a new lead ore which possibly is Galena or lead sulfide. According to Boyle the ore is peculiar because it is not mixed with any other metal. The sample that eventually made it to Boyle originated from the Upper Palatinate (Germany). Because of the Thirty Years' War that had raged in the region, this sample was found not in a mine but on the ground where the last inhabitants had left it before they fled.

By the way, you still have to pay 35 dollars for page 1 volume 1 (1879) of the Journal of the American Society (DOI), you still have to pay up for page 1 volume 1 of Liebigs Annale (1832) (DOI) and page 1 volume 1 (1957) of Tetrahedron (Elsevier) (DOI) will cost you 41 dollar. Publishers: is it about time to make some policy changes?