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Zinc deficiency depresses immunity, [236] but excessive zinc does also. [195] Despite some concerns, [237] western vegetarians and vegans do not suffer any more from overt zinc deficiency than meat-eaters. [238] Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soy foods, nuts, peas, and seeds. [237]
The Gmelin rare earths handbook lists 1522 °C and 1550 °C as two melting points given in the literature, the most recent reference [Handbook on the chemistry and physics of rare earths, vol.12 (1989)] is given with 1529 °C.
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.
Pewter has a low melting point, around 170–230 °C (338–446 °F), depending on the exact mixture of metals. [ 2 ] [ 3 ] The word pewter is possibly a variation of " spelter ", a term for zinc alloys (originally a colloquial name for zinc).
Zinc smelting is the process of converting zinc concentrates (ores that contain zinc) into pure zinc. Zinc smelting has historically been more difficult than the smelting of other metals, e.g. iron , because in contrast, zinc has a low boiling point .
Animal-based proteins tend to be high in zinc, “for example, six steamed oysters contain about 50 mg of zinc, and a grilled 3-ounce steak has about 6 mg of zinc,” says Prest.
The required temperature varies both in absolute terms and in terms of the melting point of the base metal. Examples: Iron oxide becomes metallic iron at roughly 1250 °C (2282 °F or 1523 K), almost 300 degrees below iron's melting point of 1538 °C (2800 °F or 1811 K). [5]
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