Oxygen

Depletion of the Ozone Layer in the 21st Century

A paper in Angewandte Chemie suggests that models predict that climate change will lead to an accelerated recovery of the ozone layer. However, reliable predictions are complicated by the ozone-depleting effect of N2O. If emissions of this greenhouse gas remain at current levels, by 2050 they could account for 30% of the ozone-destroying effects of chlorofluorocarbons at their peak.1

It is concluded that "the regulation of N2O levels in the atmosphere is not only important for the protection of Earth's climate (Kyoto Protocol) but also for the future evolution of the stratospheric ozone layer (Montreal Protocol). A reduction of N2O emissions would decrease the anthropogenic greenhouse effect and it would have a positive impact on the recovery of the ozone layer."

Depletion of the Ozone Layer in the 21st Century

Depletion of the Ozone Layer in the 21st Century, Dameris, Martin , Angewandte Chemie International Edition, Volume 9999, Number 9999, p.NA, (2009)

Ozone

Ozone

Ozone. Credit Mark Winter

On the Constitution of the Atmosphere.

On the Constitution of the Atmosphere., Dalton, John , Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London (1800-1843), 1/1815, Volume 2, Issue 1, p.267 - 268, (1815)

Rover Senses Carbonates

Rover Senses Carbonates

This graph, consisting of data from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signatures of carbonates - organic molecules common to Earth that form only in water. The detection of trace amounts of carbonates on Mars may be due to an interaction between the water vapor in the atmosphere and minerals on the surface.

Image credit: NASA/JPL/Arizona State University

Might future fuel cells be nickel based?

There seems to be a possibility that nickel compounds might help in the electrolysis of water, the reaction at the centre of hydrogen fuel cells. Researchers at the Joseph Fourier University in Grenoble, and at the French Atomic Energy Commission in Gif-sur-Yvette and attached a nickel compound that mimics hydrogenase enzymes (catalysts) and attached it to the surface of carbon nanotubes. This maximises the catalyst's surface area. The resulting material was tested using a proton-exchange membrane and produced hydrogen from a sulphuric acid solution. The result is only 1% as efficient than commercial platinum catalysts but is stable under typical fuel cell conditions, justifying further study.1

Silicones contaminate fuel in Southern England

For the last few days there have been many reports of damage to car oxygen sensors in England's south east. This seems to have been cause by faulty fuel supplied by some supermarker chains, including Tesco and Morrison's. Initial reports suggested the fuel was up to standard but one wonders if this is a consequence of not applying the correct tests. Expecially now that reports are emerging (for instance from The BBC) that indeed there is a contamination arising from silcon, probably from silcone contaminants. Silicones are used in diesel but damage high-tech petrol engines.

The silicones were probably introduced inadvertantly at storage rather than at the refinery stage.

This is going to get expensive for someone as it sounds as though thousands of cars have been affected.

Polonium: did it kill Alexander Litvinenko?

Polonium metal structurePolonium metal structureIt is suggested that poisoning by polonium-210 may have caused the death of Alexander Litvinenko, said to be a former Russian spy, in November 2006. Following his death at the end of November 2006, traces of polonium were found at several places he had visited before becoming ill. Before his death it was thought that thallium, or even radiothallium, might have been the cause of his illness. At the time of writing it is not clear who killed him, but not surprisingly the Russians deny it. Polonium-210 decays through the emission of α-particles and these emissions are noramlly easy to stop, but they are very dangerous if the polonium is inside the body.

Polonium is radioactive and present only in extremely low abundances in the environment. It is quite metallic in nature despite its location beneath oxygen in the periodic table. It is made in very small quantities through a nuclear reaction of bismuth. Neutron irradiation of 209bismuth (atomic number 83) gives 210polonium (atomic number 84).

209Bi + 1n → 210Po + e-

Polonium-210, 210Po, transmutes into the lead isotope 206Pb by the emission of an α-particle. The half life for this process is just over 138 days meaning that after 138 days one-half of the original 210Po has disappeared and after 2 times 138 days 3/4 has gone.

21084Po → 20682Pb + 42He

The short half life of polonium-210 and the heat generated with the above radioactive decay means that polonium metal generates considerable heat (141 W), meaning that the metal and its compounds self-heat. This is a useful property and polonium can be used as a small heat source (if expensive!). It can be used in space satellites for this purpose and is especially desirable as there are no moving parts. It was also used in the lunar rovers to keep internal parts warm during the frigid lunar nights.

Polonium metal is unique in that it is the only element whose structure (known as the α-form) is a simple cubic array of atoms in which each atom is surrounded by six other polonium atoms. On gentle warming to 36°C, this converts into a second form known as the β-form.

Polonium dioxidePolonium dioxidePolonium dissolves in acids to form pink hydrated Po(II), presumably as[Po(OH2)6]2+. This seems to oxidize to yellow Po(IV) species perhaps as a consequence of oxidizing agents produced through the α-particle induced decay of water. The polonium(II) oxide PoO is known but this oxidizes easily to the Po(IV) oxide PoO2.

Polonium dichloridePolonium dichlorideThe Po(II) halides PoX2 (X = Cl, Br, I) are known (the chloride and bromide are particularly well characterised) while all the Po(IV) halides PoX4 (X = F, Cl, Br, I) are known.

There are few crystallographically characterised polonium compounds largely because not many researchers work with polonium and the difficulties associated with characterising such radioactive compounds. The 14-electron polonium(IV) anion [PoI6]2– is strictly octahedral meaning the lone pair is sterochemically inactive.

Hydrogen oxygen alloy

Researchers at the Carnegie Institution of Washington (Washington DC, USA) have managed to make a remarkable alloy of hydrogen and oxygen from water! They used X-rays to dissociate water at high pressure to form a solid mixture, that is, an alloy, of molecular oxygen (O2) and molecular hydrogen (H2).

The researchers placed some water under an extremely high pressure, about 170,000 atmospheres (17 Gigapascals), using a diamond anvil and then beamed high-energy X-rays at the water. Nearly all the water molecules split and reformed as a solid alloy of O2 and H2. The X-rays are key to cleaving the O—H bonds in water. Without it, the water remains as a high-pressure form of ice known as ice VII. Ice VII is one of at least 15 kinds of ice that exist under various high pressure and variable temperature conditions.

Russell Hemley of the Carnegie Institution of Washington said "we managed to hit on just the right level of X-ray energy input. Any higher, and the radiation tends to pass right through the sample. Any lower, and the radiation is largely absorbed by the diamonds in our pressure apparatus."

The researchers subjected the alloy to a range of pressures and temperatures, and also bombardment with X-ray and laser radiation. Provided the alloy is kept at about 10,000 times atmospheric pressure at sea level (1 Gigapascal), it withstands the treatment. Although clearly a crystalline solid, more experiments are needed to determine the alloy's precise crystal structure.

"The new radiation chemistry at high pressure was surprising," said Wendy Mao of the Los Alamos National Laboratory in the USA. "The new alloy containing the incompatible oxygen and hydrogen molecules will be a highly energetic material." An explosive alloy!

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Copyright 1993-2011 Mark Winter [The University of Sheffield and WebElements Ltd, UK]. All rights reserved.