Clusters of zinc atoms then mix with a reactive gas, usually oxygen, and cool to a solid.

FORBES: The science of small

He read about something called direct-reduced iron, a technique for smelting without melting--removing the oxygen from iron ore while it's still solid, that is.

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Oxygen generators contain sodium chlorate and iron powder -- solid chemicals that are mixed and cast into a solid shape.

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The gas is then fed into a stack of solid oxide fuel cells, where a chemical reaction between hydrogen and oxygen occurs, producing electricity, water vapor and a tiny amount of carbon dioxide.

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Officials packed long metal tubes -- called "carrier pigeons" -- with oxygen, vaccines and sustenance, liquid proteins and vitamins at first because the men were not ready for solid food.

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