Reversible operations in metallurgy

3 On the following, see Klein [1994a] p. 122ff., and [1994b] pp. 173f. and 180ff. 

4 See Beretta [1997]. For life and work of Agricola, see Darmstaedter [1998] Wilsdorf [1956] and Gillispie [1970-1980] voL Ip. 77ff. 

5 We here use analysis and synthesis in the contemporary meaning that does not distinguish between stoichiometric and non-stoicliiometric compounds. The extraction of non-precious metals, usually available as oxides or sulfides, through reduction was not recognized as a chemical procedure prior to Stahl s phlogiston theory, but considered to be a mere smelting of metals fiom the ore. 

6 For this process, see book IX of Agricola s De re metallica (Agricola [1556]). 

In place of lead, meicuiy was also used as a means of extraction, first for gold and later for silver as well. In this case a silver or gold amalgam is produced, which is then heated to separate the mercury from the silver or gold. 

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