plumbagon.

Etymology: < classical Latin plumbāgō a type of lead ore, also a plant (both in Pliny) < plumbum lead (see plumb n.¹) + -āgō , suffix forming nouns: in the sense ‘a type of lead ore’ the Latin word is after ancient Greek μολύβδαινα as used in Hellenistic Greek by Dioscorides (see molybdena n.). Adopted as a genus name (see sense 1b) by Linnaeus Species Plantarum (1753) I. 151, after J. Pitton de Tournefort Inst. Rei Herbariæ (ed. 2, 1700) I. 140. Compare Middle French plombage graphite (1556, translating Latin plumbāgō ), French plumbago plant of the genus Plumbago (1765). Compare also plumbagine n. and the Romance words cited at that entry.In Dioscorides (5. 85), μολύβδαινα ( < μόλυβδος lead) was applied to a mineral substance, yellow oxide of lead (PbO), especially the litharge produced in the extraction of gold and silver from ores containing lead. By Pliny this is Latinized as molybdaena , and also rendered (34. 168) by plumbāgō , which, as well as galēna , were applied by him to the yellow oxide, but which probably included as an inferior variety the sulphide (PbS), called by Dioscorides μολυβδοειδὴς λίθος , ‘lead-like stone’, the modern galena n. For the plant too Pliny uses both molybdaena and plumbāgō . In the French translation (1572) of Mattioli's Commentary on Dioscorides, μολύβδαινα (corresponding to plumbago ) is rendered plombagine (and in the Italian piombaggine ), and is stated to be identical with litharge; but other ores may have been included. Thence the explanations of the word in Cotgrave (1611) and other English writers down to Bailey; compare sense 2 and plumbagine n. 1. In Holland's translation of Pliny, classical Latin plumbāgō is rendered litharge . In the 16th cent., to Agricola and others in Germany practically interested in mining, post-classical Latin plumbago mainly meant lead sulphide, but also included other substances similar to this in appearance, and in the property of staining the fingers and marking paper, especially the native sulphides of antimony and molybdenum, stibnite n. (Sb₂S₃) and molybdenite n. (MoS₂), and the mineral graphite. In 1551 Christoph Entzelt (Encelius) of Saalfeld, while identifying Pliny's molybdaena , galēna , and plumbāgō , distinguished the ‘productive’ species (i.e. the oxide and sulphide of lead) from the ‘barren’ (sterilis ), which yielded no lead, and was mainly graphite; the latter was described by Ferrante Imperato in 1599 as employed in the grafio piombino , ‘leaden pencil’. In 1779 Scheele found that certain samples of the ‘barren’ plumbago, on being burnt, were dissipated into carbonic acid gas, and that in fact they consisted of carbon: see quot. 1786 at sense 3. In 1789 Werner and Karsten proposed the name graphite n. instead of the ambiguous ‘plumbago’. But its composition was still disputed. An analysis, made by French chemists in 1786, had given, after volatilization, a residue of iron, and plumbago was pronounced a carburet of iron (see quot. 1795 at sense 3). This view prevailed until Karsten in 1826 and Sefström in 1829 proved that the iron was only an impurity in the specimens analysed, and that graphite or plumbago was, as Scheele had said in 1779, really a mineral form of carbon. See further J. W. Evans in Trans. Philol. Soc. (1908) 133–79.