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  2. Prices of chemical elements - Wikipedia

    en.wikipedia.org/wiki/Prices_of_chemical_elements

    This is a list of prices of chemical elements. Listed here are mainly average market prices for bulk trade of commodities. Data on elements' abundance in Earth's crust is added for comparison. As of 2020, the most expensive non-synthetic element by both mass and volume is rhodium.

  3. Oxygen-free copper - Wikipedia

    en.wikipedia.org/wiki/Oxygen-free_copper

    This is a 99.99% pure copper with 0.0005% oxygen content. It achieves a minimum 101% IACS conductivity rating. This copper is finished to a final form in a carefully regulated, oxygen-free environment. Silver (Ag) is considered an impurity in the OFE chemical specification. This is also the most expensive of the three grades listed here.

  4. Silver standards - Wikipedia

    en.wikipedia.org/wiki/Silver_standards

    Ninety-one (91) zolotniks have the equivalent millesimal fineness of 947[9]. Thus, the alloy contains 94.79% pure silver and 5.21% copper or other metals. [4] [5] Sterling silver has a millesimal fineness of 925. The sterling silver alloy is 92.5% pure silver and 7.5% copper or other metals.

  5. Nines (notation) - Wikipedia

    en.wikipedia.org/wiki/Nines_(notation)

    For example, a N2.0 gas is 99% (two nines) pure and 1% impurities by volume; a N6.0 gas is 99.9999% (six nines) pure, with 1 part per million (1 ppm or 1 vpm, volume per million) impurities. [7] Intermediate values indicate the digit following the last nine. For example, N4.6 estimates a purity level of 99.996% (four nines followed by a six). [7]

  6. 99% - Wikipedia

    en.wikipedia.org/wiki/99%

    Main page; Contents; Current events; Random article; About Wikipedia; Contact us

  7. Standard deviation - Wikipedia

    en.wikipedia.org/wiki/Standard_deviation

    Stock A over the past 20 years had an average return of 10 percent, with a standard deviation of 20 percentage points (pp) and Stock B, over the same period, had average returns of 12 percent but a higher standard deviation of 30 pp. On the basis of risk and return, an investor may decide that Stock A is the safer choice, because Stock B's ...

  8. Isopropyl alcohol - Wikipedia

    en.wikipedia.org/wiki/Isopropyl_alcohol

    Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable, organic compound with a pungent alcoholic odor. [9]Isopropyl alcohol, an organic polar molecule, is miscible in water, ethanol, and chloroform, demonstrating its ability to dissolve a wide range of substances including ethyl cellulose, polyvinyl butyral, oils, alkaloids, and natural ...

  9. 68–95–99.7 rule - Wikipedia

    en.wikipedia.org/wiki/68–95–99.7_rule

    For an approximately normal data set, the values within one standard deviation of the mean account for about 68% of the set; while within two standard deviations account for about 95%; and within three standard deviations account for about 99.7%.