ChemWeb Newsletter

Not a subscriber? Join now.November 28, 2006


The Alchemist this week discovers why his 500-year old crucible is still working well and learns that Mendeleev may have had a sneak peak at other attempts at the "periodic table" before he devised his own. This week, we also hear about a dip test for cocaine that is as easy as a pregnancy test. We ought to mind the hydrophobic gap this week too as high-energy X-rays reveal that the interaction between water and a surface is no gas. Finally, antibacterial wrappers, we also learn, will not only help protect you from deadly E coli but could also give tasteless vegetables a flavor boost.

A compound of aluminum silicate known as mullite (Al6Si2O13) is the secret component of the alchemists' crucibles used almost half a millennium ago across Europe and known to be among the most thermal and chemically resistant objects in the alchemical den. Researchers at University College London and Cardiff University have used petrographic, chemical, and X-ray diffraction analysis to demonstrate that crucible makers in Hesse, Germany, used an advanced material only properly characterized in the last century. UCL archeologist Marcos Martinón-Torres explains: "Our analysis of fifty Hessian and non-Hessian crucibles revealed the secret component." The crucible makers were not aware of mullite specifically, but they knew that firing kaolinitic clay at 1100 Celsius would make crucibles tough enough for alchemical reactions.

Chemical philosopher Eric Scerri of the University of California Los Angeles claims in a new book entitled simply: "The Periodic Table", that contrary to popular opinion, Dmitri Mendeleev did not work entirely in isolation in the Siberian wilderness. Rather, Scerri says, Mendeleev spoke all the major European languages, was familiar with the scientific literature of the time, and had traveled in Europe. "He mentioned the precursors of the periodic table, but not the ones who actually devised systems," he says, "He surely must have known about them." One of those primordial periodic tables was developed by a French geologist named Alexandre Emile B guyer de Chancourtois. He discovered the periodic system itself, but unfortunately his publisher did not have the expertise to print the complex diagram that de Chancourtois devised when he submitted his paper. As a result, Chancourtois received very little credit for the periodic table, and is not widely known. The name of Mendeleev on the other hand is inextricably woven into the fabric of chemistry.

A new generation of diagnostic tests based on gold nanoparticles and aptamers could be as simple to operate as a pregnancy test kit, according to researchers at the University of Illinois in Urbana, providing emergency rooms with a way to identify the cause of a poisoning of drug overdose very quickly. Yi Lu and colleagues say their new approach to diagnostics is as reliable as conventional laboratory methods. They have demonstrated proof of principle with a dip-stick for detecting cocaine in biological samples such as saliva, urine, and blood serum. It is possible to find a suitable single strand of DNA, an aptamer, for almost every target molecule, says Lu. "The broad practical application of aptamers has thus far not realized its promise in practical diagnostics because the corresponding tests could not be made sufficiently user-friendly for the average user, who has not had laboratory training."

An international team has used high-energy X-rays at the European Synchrotron Radiation Source (ESRF) to reveal details of what occurs in the gap between water and a hydrophobic surface. The new insights could help explain in finer detail why water and oil don't mix. Scientists from the Max Planck Institute for Metals Research in Germany and the University of South Australia in Adelaide, and the ESRF carried out experiments on silicon wafers coated with octadecyl-trichlorosilane. Their high-resolution in situ X-ray study of the hydrophobic gap show that contrary to earlier studies, gas molecules do not apparently play a role in the structure of water at such interfaces.

A new, improved wrapping material for fruit and vegetables can kill pathogenic bacteria such as Escherichia coli. The material is made from apple puree and oregano oil and not only acts as a natural antibacterial barrier but gives often insipid veggies a flavor boost, say its developers. The material has been developed by a team of scientists from the U.S. Department of Agriculture (USDA) and the University of Lleida in Spain in response to the growing number of deadly outbreaks of E coli poisonings traced back to contaminated foods. Full results will be published in the Journal of Agricultural and Food Chemistry on November 29. You might say, that's a wrap.