Metals: French classification

In the manufacture of zinc white by the French process, metallic zinc is melted, evaporated and oxidized in the vapor state to zinc oxide with air. If the starting material is insufficiently pure, the zinc has to be purified by evaporation and condensation prior to the oxidation step. The size and shape of the zinc oxide crystals can be controlled by the oxidation conditions. After combustion the ZnO is precipitated from the ZnO/air mixture in settling chambers, in which classification of the zinc oxide particles takes place according to their size. 

A decree of the French Home Secretary from June 30, 1983 on the classification of construction materials according to their fire resistance and on the definition of test methods has rated common metals such as aluminium alloys and steel MO , which means that under the conditions of a fire, these materials are considered to be incombustible. 

To sum up, most French chemistry textbook authors considered Mendeleev s periodic classification as a defective and unfeasible solution for a problem already solved in a more pragmatic and satisfactory way. More than a symptom of a strong anti-atomist resistance to the periodic classification, the lack of interest in Mendeleev s achievement could be the expression of the increasing autonomy of the educational sphere inhabited by a crowd of teachers and textbook writers who were mainly concerned with didactic efficiency. For them, the benefits of Mendeleev s system did not compensate for the loss of the practical division between metals and non-metals and nobody was ready to break with this long-standing tradition in chemistry teaching (Figure 5.2). 

In 1875, just a few years after Mendeleev had pubhshed his periodic classifications, the pharmacist and professor of chemistry Rafael Saez Palacios (1808-1883) wrote a two-volume treatise on chemistry intended for students of pharmacy. Saez had already published several translations of leading chemistry textbooks, including Berzelius s treatise and a number of French books that had adopted natural classifications. Like many other textbook authors, he devoted a full section to classifications before the chapters on metals, describing Thenard-Regnault s and Berzehus s artificial classifications as well as many examples of natural classifications. He... 

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