![]() ![]() A substance identified primarily by an EC or list number may be linked with more than one CAS number, or with CAS numbers that have been deleted. The CAS number is the substance numerical identifier assigned by the Chemical Abstracts Service, a division of the American Chemical Society, to substances registered in the CAS registry database. CAS (Chemical Abstract Service) registry number The EC or list number is the primary substance identifier used by ECHA. If the substance was not covered by the EC Inventory, ECHA attributes a list number in the same format, starting with the numbers 6, 7, 8 or 9. More information about the EC Inventory can be found here. ![]() The EC Inventory is a combination of three independent European lists of substances from the previous EU chemicals regulatory frameworks (EINECS, ELINCS and the NLP-list). The EC Number is the numerical identifier for substances in the EC Inventory. Some substance identifiers may have been claimed confidential, or may not have been provided, and therefore not be displayed. The substance identifiers displayed in the InfoCard are the best available substance name, EC number, CAS number and/or the molecular and structural formulas. I was certainly inclined to believe they were right.The ‘Substance identity’ section is calculated from substance identification information from all ECHA databases. Lead study author Marcos Martinon-Torres, now at Cambridge University, admits he was surprised by the findings, calling the 1970s research “remarkably convincing. “It would have been an attractive explanation to both scholars and the public,” Murowchick observes, “as it suggested a nice parallel to the stories passed down by early Chinese historians about the First Emperor of Qin's fascination-perhaps obsession-with discovering an elixir of immortality for himself.” “It was not a wild idea to suggest that Qin workshops intentionally treated their bronzes with chromium to prevent corrosion.” Robert Murowchick, associate director of Boston University’s Center for the Study of Asia, says that the original chromium idea was a reasonable theory for people to have embraced for so long. Thomas Chase, a conservation expert in Chinese bronze technology, says that “ team has done a wonderful job in disproving the chromium-plating theory and an offering a viable alternate explanation.” The study’s analyses of multiple materials-metal, lacquer, and soil-he adds, “are exactly what is necessary to help us understand long-term corrosion and preservation of metal artifacts." The upshot? The chromium came from the lacquer, and the preservation came from the dirt. Further analysis revealed that the lacquer was actually the source of the chromium detected by earlier researchers.Ī study of the site soil yielded more clues: It’s alkaline and finely grained, which limit aeration and organic growth-all factors that can contribute to the stability of metal objects over time. It was generally absent on the best-preserved parts of the bronzes. It’s common where the metal would’ve connected to wood and bamboo handles, shafts, fittings, and fasteners, which would’ve been lacquered and then painted. The large sample size allowed them to see where chromium appears-and where it doesn't. The researchers suggested the weapons could’ve been dipped in a chromium oxide solution, a method known as chromate conversion coating-a technique technically different from modern chrome plating, which involves chromium metal. After early excavation reports suggested a surface treatment could explain the exquisite preservation of the 2,200-year-old bronze weapons, Chinese scientists used a then-pioneering analysis called compositional mapping to reveal a layer of chromium on a small sample of the weapons. This theory dates to the 1970s, the decade when the World Heritage site was first discovered. The claim is even on a plaque at the site’s museum in Xi’an. Yet for 40 years, an alternate theory has circulated in scholarly circles and the popular media: Chrome plating was invented in the third century B.C in China and used to prevent the bronze weapons buried with the Terracotta Army in Emperor Qin’s tomb from corroding. Experiments with this anti-rust technology began in Europe in the 19th century. ![]() ![]() If your bathroom faucets look like shiny silver, they’re likely chrome plated. ![]()
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