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  2. Prices of chemical elements - Wikipedia

    en.wikipedia.org/wiki/Prices_of_chemical_elements

    In the form of boric acid, price per boron contained. Min. 99% pure. 6: C: Carbon: 2.267: 200 (5.54 × 10 18 kg) 0.122: 0.28: 2018: EIA Coal [19] In the form of anthracite, price per carbon contained, assuming 90% carbon content. There is a wide variation of price of carbon depending on its form.

  3. 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]

  4. Sterling silver - Wikipedia

    en.wikipedia.org/wiki/Sterling_silver

    Fine silver, which is 99.9% pure silver, is relatively soft, so silver is usually alloyed with copper to increase its hardness and strength.Sterling silver is prone to tarnishing, [1] and elements other than copper can be used in alloys to reduce tarnishing, as well as casting porosity and firescale.

  5. Fineness - Wikipedia

    en.wikipedia.org/wiki/Fineness

    A refiner doing $1 billion of business each year that marked .980 pure bars as .999 fine would make about an extra $20 million in profit. In the United States, the actual purity of gold articles must be no more than .003 less than the marked purity (e.g. .996 fine for gold marked .999 fine), and the actual purity of silver articles must be no ...

  6. 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.

  7. High availability - Wikipedia

    en.wikipedia.org/wiki/High_availability

    High availability (HA) is a characteristic of a system that aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period. [1] ...

  8. Primary production - Wikipedia

    en.wikipedia.org/wiki/Primary_production

    Gross primary production (GPP) is the amount of chemical energy, typically expressed as carbon biomass, that primary producers create in a given length of time.Some fraction of this fixed energy is used by primary producers for cellular respiration and maintenance of existing tissues (i.e., "growth respiration" and "maintenance respiration").

  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%.