It is difficult to define the term “refractory compound,” since any subdivision into refractory and nonrefractory compounds is arbitrary and presupposes the fixing of some melting point boundary above which chemical compounds are considered to be refractory. Such a boundary has been repeatedly established and has gradually been shifted to regions of higher and higher temperatures, from 1000°C in the second half of the nineteenth century to 2000°C in the first half of the twentieth century, and currently it is very often assumed to be 3000°C.
KeywordsEntropy Titanium Porosity Phosphorus Sulfide
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