Chemistry news, articles, and more

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.

Do you want your own chemistry blog?

I'm slowly expanding some of the functionality on the WebElements periodic table site and we now have the bare bones of a news and forums site here (the current URL will switch to the main WebElements site in a while). This part of the site will also house chemistry information pages in a "book " format (this will also be open to contributors in a while) and some other features.

The system I am using does allow individual users to post their own blogs and it seems to me that some of you have something to say. Chemists don't seem to be natural bloggers, however, this is an offer for some of you chemists out there to have your own blog on one of the highest profile chemistry sites around.

This is an experiment and I want to offer the facility only to a few chemists just now. If you are interested please contact me via the contact form and tell me who you are, what you do (briefly!) and if it seems appropriate I'll set you up with your own blog. You shouldn't feel any pressure to write every day or even every week, just when you have something to say. All I ask is that you keep to chemistry, at least most of the time, and keep it polite.

A little more cash for English University Science

The Higher Education Funding Council for England is to provide £75 million in additional funding to support very high cost science subjects, which are strategically important to the UK economy and society but vulnerable because of relatively low student demand.

The funding over three years from 2007-08 will support chemistry; physics; chemical engineering; and mineral, metallurgy and materials engineering - to help maintain provision in these subjects in universities and colleges while demand from students grows.

The additional funding for chemistry, physics and the other subjects mentioned is said to increase the HEFCE teaching grant for these subjects by approximately 20 per cent or by one thousand pounds per student.

  1. Terms and conditions will be attached to the funding, which will include a requirement that institutions maintain teaching capacity in the subjects concerned. The money will be allocated by formula to reflect the scale of teaching activity at each institution in the subjects concerned. The details of the allocation method will be considered by the HEFCE Board in January.
  2. Full details about the range and scope of the £160 million programme of work to support strategically important and vulnerable subjects is available in the HEFCE October 2006 update to the Secretary of State
Tags:

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!

Darwin online

Good to see that the complete works of Charles Darwin, one of the greatest scientists, are being published online by Cambridge University. Darwin Online features many newly transcribed or never-before-published manuscripts and is worth anyone's time to browse around for a while. The great English naturalist Charles Darwin (1809-1882) revolutionized our understanding of life on earth.

"The idea is to make these important works as accessible as possible; some people can only get at Darwin that way," said Dr John van Wyhe, the project's director. "It is astonishing to see the notebook that Darwin had in his pocket as he walked around the Galapagos - the scribbled notes that he took as he clambered over the lava," said Randal Keynes, the great-great-grandson of Charles Darwin.

Darwin Online is educational and non-profit. Darwin Online received a grant of £286,000 (or $530,000) to fund the research and activities that produced the website. This funding ends in October 2008. Why not head over to the site and donate a little cash to advance the project?

Cubic nitrogen with single N-N bonds

Single-bonded cubic form of nitrogenSingle-bonded cubic form of nitrogenEveryone knows that elemental nitrogen exists in the atmosphere as dinitrogen, N2. There is a triple bond between the two nitrogen atoms. This is true - but under certain conditions, a fascinating N-N single bonded phase has been characterized.1

In 1985 it was predicted that at high pressure, nitrogen would transform to a solid with a single-bonded crystalline structure called polymeric nitrogen. Later, it was proposed that it whould have a cubic gauche (cg-N) structure. Experimental evidence was scant however until 2004 when a team of scientists from Germany and Russia managed to make the compound directly from molecular nitrogen at temperatures above 2000 K and pressures above 110 GPa using a laser-heated diamond cell. The material was characterized by X-ray and Raman scattering methods we have identified this as the polymeric nitrogen (cg-N).

The phase is a stiff with a bulk modulus ≥300 GPa. This is characteristic of strong covalent solids. The polymeric nitrogen is metastable. The structure of N is polymeric with each nitrogen bound to three other nitrogen atoms. At a pressure of 115 GPa, each N-N bond length is 1.346 ± 0.004 Å. The N-N-N angles are all about 108.8°, very close to the ideal tetrahedral angle of just over 109°.

It did not prove possible to recover the polymeric nitrogen by releasing the pressure - in other words the polymer reverts to normal dinitrogen. The authors speculate that this form of nitrogen is a new class of single-bonded nitrogen materials that may have unique energy capacity properties (more than five times that of the most powerful energetic materials).

Welcome back element 118 (ununoctium)

Experiments conducted at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research) at Dubna in Russia indicate that element 118 (ununoctium, Uuo) was produced. Not too much though, one atom in the spring of 2002 and two more in 2005.1,2

The 2002 experiment involved firing a beam of 4820Ca at 24998Cf. The experiment took 4 months and involved a beam of 2.5 x 1019 calcium ions to produce the single event believed to be the synthesis of 294118Uuo.

24998Cf + 4820Ca → 294118Uuo + 31n

This ununoctium isotope loses three alpha particles in rapid succesion:

294118Uuo → 290116Uuh + 42He (1.29 milliseconds)

290116Uuh → 286114Uuq + 42He (14.4 milliseconds)

286114Uuq → 282112Uub + 42He (230 milliseconds)

The 282112Uub species then undergoes spontaneous fragmentation (denoted SF) to other species. It took a few years to carry out enough research to properly characterize the decompoition products.

In 2005 a similar experiment but with more sensitive detectors and a total beam dose of 1.6 x 1019 calcium ions resulted in the detection of two further events arising from the formation of 294118Uuo.

This work is particularly significant given the scandal associated with the first report (now withdrawn) of element 118.

21st Century science - dumbed down?

Arguments continue over science education in the UK.

Twenty First Century Science is a suite of new GCSE science courses for 14- to 16-year-olds and all schools in the UK can start the courses from September 2006. Schools can continue to offer separate Chemistry, Physics, and Biology courses.

Critics such as Sir Richard Sykes (rector of Imperial College London) is among many attack the new qualification. He warned a "dumbed down syllabus" may stop those who did not study chemistry, physics and biology individually from getting into good universities. Sir Richard Sykes stated on BBC News: "If you wish to have a dumbed-down syllabus for the general population that's fine. But for those who really want to go on and study a subject in depth, and particularly go to a good university like Imperial, then they'll never get there unless they study the individual subjects and take A-levels in these individual subjects." He wrote in a report from the Institute of Ideas think tank that: "A science curriculum based on encouraging pupils to debate science in the news is taking a back-to-front approach... Science should inform the news agenda, not the other way round."

David Perks who is head of physics at Graveney School in London, describes the changes as a "dumbing down" of the subject in a critical essay published by the Institute of Ideas (it is this essay that triggered the argument).

Baroness Mary Warnock said: "What counts as an issue to be debated in class is largely, as David Perks points out, dictated by the press. Far too much teaching at school has already degenerated into this kind of debate, more suitable for the pub than the school room."

However, not unexpectedly, the UK Department for Education and Skills said the qualification would be academically rigorous while encouraging more young people to consider studying science post-16. The British Association for the Advancement of Science and the Royal Societyseem to support the new course.

This project began because the Qualifications and Curriculum Authority (QCA) was asked by the government to explore ways to modernise the science curriculum which was criticised in some quarters. Pilot course started in September 2003 at about 80 pilot schools.

The BBC article on this topic has some interesting reader responses!

Germanium nanocrystals melt 200°C higher in glass than in bulk

Scientists at the Lawrence Berkeley National Laboratory in California, USA, have discovered that nanocrystals of germanium embedded in silica glass don't melt until the temperature rises almost 200 degrees Kelvin above the melting temperature of germanium in bulk. What's even more surprising, these melted nanocrystals have to be cooled more than 200 K below the bulk melting point before they resolidify. Such a large and nearly symmetrical "hysteresis" -- the divergence of melting and freezing temperatures above and below the bulk melting point -- has never before been observed for embedded nanoparticles.

"Melting and freezing points for materials in bulk have been well understood for a long time," says Eugene Haller (one of the authors) , "but whenever an embedded nanoparticle's melting point goes up instead of down, it requires an explanation. With our observations of germanium in amorphous silica and the application of a classical thermodynamic theory that successfully explains and predicts these observations, we've made a good start on a general explanation of what have until now been regarded as anomalous events."

The research was conducted because the properties of germanium nanoparticles embedded in amorphous silicon dioxide matrices have promising applications. "Germanium nanocrystals in silica have the ability to accept charge and hold it stably for long periods, a property which can be used in improved computer memory systems. Moreover, germanium dioxide (germania) mixed with silicon dioxide (silica) offers particular advantages for forming optical fibers for long-distance communication."1

Deadly poison hydrogen sulfide induces suspended animation

Researchers from the Massachusetts General Hospital in Boston (USA) have announced that hydrogen sulfide (sulphide) gas, H2S, can induce a state of suspended animation in mice while maintaining normal blood pressure. It is hoped that this result eventually will help in the treatment critically-ill patients. This result was presented at the American Physiological Society conference, "Comparative Physiology 2006: Integrating Diversity," in Virginia Beach, Virginai, USA, October 2006.

Hydrogen sulfide (sulphide) gas, sometimes called sewer gas, produces a noxious odour often described as a rotten egg smell. This highly toxic gas occurs naturally in swamps, some springs, and volcanoes.

The researchers administered 80 parts per million of H2S gas to their and found that their:

  • heart rate fell from 500 beats per minute to 200 beats per minute
  • respiration rate decreased from 120 breaths to 25 breaths per minute
  • core body temperature fell from 38° C to 30° C
  • activity level fell dramatically, moving only when the researchers touched them or shook their chambers

After the mice returned to breathing normal air they quickly returned to normal. Normally, as oxygen consumption goes down and heart rate decreases, blood pressure decreases also. Since the heart rate of the mice fell by more than 50%, the researchers expected blood pressure to fall, but it didn't.

"These findings demonstrate that mice that breathe 80 parts per million of hydrogen sulfide become hypothermic and decrease their respiration rate, heart rate and cardiac output without affecting stroke volume or mean arterial pressure," the authors said. This line of research could have a variety of helpful applications, including sustaining the function of organs of critically ill people, Ichinose said. It may also be possible to use the finding for patients undergoing surgery. This would be an advance, because anesthesia usually causes blood pressure to drop.

WebElements: the periodic table on the WWW [http://www.webelements.com/]

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