ChemWeb Newsletter

Not a subscriber? Join now.February 27, 2007

contents
overview

This is the sixty-first issue of the "new" Alchemist and as you might expect having reached that tender age, we've expanded somewhat, so from this issue onwards there is more chemistry that matters. In this week's issue, new symbolism in the world of ionizing radiation, a rubber band theory that requires no stretch of the imagination to work, and how a combined effort can single out the murder weapon. Also in this week's issue, new catalysts could make use of wasted natural gas that is simply vented and flared at oil wells and archaeological evidence that Christopher Columbus' fellow travelers struggled to find enough silver. Finally, crumpling hydrogels could give chemists a taste for plastic origami and US researchers receive major grant to fuel research into non-fossil energy sources.




It has to be the least subtle signage update ever, but the International Atomic Energy Agency (IAEA) is adding a skull and crossbones and the figure of a person running away to its warning symbol for dangerous ionizing radiation. According to the IAEA, until now people finding hazardous materials marked with the old sign of the three-petal "trefoil" occasionally ignore the warning and open protective lead casings only to expose themselves to a potentially lethal dose of radiation depending on the contents. The Authority believes that only people educated in identification of the old trefoil recognize it as a hazard whereas the meaning of the new sign should be more immediately obvious. The trefoil remains, but has wavy arrows emanating from it to symbolize radiation. Many radiation source manufacturers are already planning to use the symbol on their large products. Strategies to apply the symbol on existing large sources are being developed by the IAEA.





Stretch a rubber band only a little and it obeys Hooke's law well, give it more of a tug and that simplistic theory breaks down and the material's behavior becomes altogether less linear. Explaining why the theory snaps when rubber bands or stretched too far has vexed scientists for decades. Now, Paul Goldbart of the University of Illinois at Urbana-Champaign has modified the classical theory of flexible cross-links between polymer chains in rubber and similar materials. In their model, rubber's entropy comes not only from the vibration of molecules between the crosslinks, but also from movement of the crosslinks themselves, which elegantly explains stretching behavior that previous generations of scientists had simply overlooked.





Combining results from inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscope-energy disperse X-ray microanalysis (SEM/EDX) could soon be used by forensics experts to discriminate between metallic implements that have injured or killed a person. Such technology would be especially useful where an unambiguous identification of the weapon based on entry wound examination is not possible. The method is now gradually being utilized by the police, but it is a new technique and while it provides more stable evidence than other methods, there is some way to go before it is used widely. The researchers are currently selecting other implements to examine using their technique. They point out that clotting blood does not influence the results.





A group of newly discovered catalysts could provide a solution to the slow-burning problem of finding an economical way to exploit natural gas wasted as "flare" from oil wells. Johannes Lercher and colleagues a Dow Chemical in Midland, Michigan, have developed stable, lanthanum-based catalysts that can convert methane and hydrogen chloride efficiently into the useful starting material of methyl chloride. The researchers used activity and spectroscopic measurements to demonstrated that lanthanum oxychloride (LaOCl), lanthanum trichloride (LaCl3), and lanthanum phases with intermediate coordination of chlorine are all active for this reaction. Methyl chloride can in turn be converted to olefins with known catalysts, thus providing an effective means to exploit methane as a chemical industry feedstock.





New evidence has been found of the first-known European extraction of silver in the New World. According to archaeologist Kathleen Deagan of the University of Florida, the last inhabitants of Christopher ColumbusÕ first settlement, at La Isabela on modern-day Dominican Republic's north coast, desperately tried to extract silver from lead ore that had originally been brought from Spain but abandoned their failed efforts in 1498. Deagan collaborated with geoscientists and metallurgists to figure out how a smelting operation at the site that apparently used 200 pounds of the silver-bearing lead ore galena functioned. "We first thought they mined the galena locally to extract lead for weapons, such as lead shot and musket balls or ship sheathing," explains Deagan, "But an isotope analysis showed it was actually from Spain." Further metallurgical analysis shows that the settlers were desperately trying to extract silver before they finally abandoned the settlement.





A hydrogel that crumples up like thin slices of potato being cooked to make chips has been developed by Yael Klein and co-workers from the Hebrew University of Jerusalem. The millimeter thick material crumples into a predetermined structure when heated but reverts to its flattened state when cooled in water. The material is a cross-linked elastic hydrogel composed mainly of polymeric N-isopropylacrylamide (NIPA). This material shrinks by driving out water above 33 Celsius. Dilute NIPA gels shrink the most because it contains more water but high NIPA concentrations shrink only a little. By creating a disc with varying concentrations of NIPA across the material, Klein's team created a thin sheet that shrinks a lot in some places but only a little in others forcing it to crumple under the stress of heating. The team suggests the materials could be used in smart applications to make folded objects that form in response to heat, and even pH, light, or the presence of an additive, such as glucose.





Dn Gervasio's team at Center for Applied NanoBioscience at Arizona State University is set to receive a $1.5m grant from the Department of Energy to develop new fuel cells for renewable energy and the so-called hydrogen economy. The funding will allow the team to improve the efficiency of their fuel cell designs significantly and circumvent the problem of excess heat generation. By designing a membrane that operates at high temperatures (a medium oven setting of 120 Celsiua), Gervasio and colleagues want to reduce both the amount of heat management needed to operate the fuel cell and its overall size, weight and costs. The improved fuel cells will enable the technology to move into cars, homes, and remote power facilities where the energy input from renewable sources such as solar and wind will be more effectively utilized.