Abstract
THIS is a set of cardboard pieces printed with the symbols of elements and common radicles, and graduated in size according to predominant valency; positive radicles are blue, negative are pink. The formulæ are made up by placing the appropriate elements or radicles side by side. It is at once evident that ferrous phosphate is Fe3(PO4)2, and ferric phosphate FePO4, while such combinations as CaCl or NaCl2 appear wrong at once. The idea, so far as it goes, is ingenious, and a great deal of facility in writing formulae may be gained by an eitercise more like play than work; moreover, the method cannot foster the misconception of rigid bonds. It is suggested that he pieces can be used to make constitutional formulæ—sulphuryl chloride and sulphuric acid are given as examples. It is evident, however, that before pupils get to the stage of considering the relation of these compounds, the device should lave served its purpose.
Set of Cards for Teaching Chemical Formulae and Equations.
Devised by Mrs. M. Partington. (London: Baird and Tatlock, Ltd., n.d.) 1s. 4d.
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Set of Cards for Teaching Chemical Formulae and Equations . Nature 107, 296 (1921). https://doi.org/10.1038/107296c0
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DOI: https://doi.org/10.1038/107296c0