Noble gas in the United States alone. For large-scale use, helium is extracted by fractional distillation from natural gas, which can contain up to 7% helium. Neon, argon, krypton, and xenon are obtained from air using the methods of liquefaction of gases, to convert elements to a liquid state, and fractional distillation, to separate mixtures into component parts. Helium is typically produced by separating it from natural gas, and radon is isolated from the radioactive decay of radium compounds. The prices of the noble gases are influenced by their natural abundance, with argon being the cheapest and xenon the most expensive. As
Copia: Foundations of the Abundant Style 11 separate methods of using abundant subject matter. Here Erasmus uses a more dialectical approach, and typically gives a few lines of theory followed by many illustrations from classical sources. Erasmus purpose was to contribute to the existing scholarship on style. To that end, he put forth in "De Copia" that style must be abundant in order to be effective, and that the abundance consists of two primary elements: variety of expression and variety of subject matter. Variety, he says, “is so powerful in every sphere that there is absolutely nothing, however brilliant, which is not dimmed if not commended