Among these are silica, obtained by calcination (heating) of silica gel; high-purity alumina, prepared by the calcining of specially prepared aluminum hydroxide; and silica-alumina mixtures.
Much use is also made of the so-called direct oxidation-reduction process, whereby PuO2 is reduced with calcium metal to plutonium metal and a calcium oxide slag: The hydrometallurgical processing of uranium ores is frequently preceded by a high-temperature calcination step.
The Bayer process involves four steps: digestion, clarification, precipitation, and calcination.
Lavoisier saw Priestley's discovery of oxygen in 1774 as the key to the weight gains known to accompany the burning of sulfur and phosphorus and the calcination of metals (oxide formation).
The hydrometallurgical processing of uranium ores is frequently preceded by a high-temperature calcination step.
For nuclear applications, thoria is prepared by calcination of thoroughly purified Th NO3 4.
Inflammation (that is, combustion) and calcination were thus both processes in which phlogiston was released.
But about half of the CO2 from cement cannot be eliminated — it is produced in the reaction, called calcination, that occurs as the limestone (which consists of calcium carbonate) is being burned.
The increase in weight on calcination meant, in the light of this principle, that calcination was not a decomposition, as the phlogiston theorists would have it, but the formation of a more complex compound.
Johann Joackim Becher (1635 82) modified these ideas at the end of the 17th century, arguing that the calcination of metals is a kind of combustion involving the loss of what he called the principle flammability.
He showed that the calcination of metals led to a gain in their weight equal to the weight of oxygen lost by the surrounding air.
