Chem. [f. SOD-A1 + -IUM. Named by Davy (1807).]
1. An elementary alkaline metal (isolated by Davy in 1807), forming the basis of SODA, closely resembling potassium in its appearance and properties, and occurring most commonly in the chloride (common salt). Symbol Na (for Natrium).
1807. Davy, in Phil. Trans. (1808), I. 32. Potassium and Sodium are the names by which I have ventured to call the two new substances. Ibid. (1811), Chem. Philos., 331. I discovered sodium a few days after I discovered potassium, in the year 1807.
1815. J. Smith, Panorama Sci. & Art, II. 395. Sodium has a much higher point of fusion than potassium.
1856. Miller, Elem. Chem., Inorg., 743. Sodium has a bluish white colour; in appearance and properties it much resembles potassium, but is somewhat more volatile.
1879. Proctor, Pleas. Ways Sci., i. 1. A certain double dark line in the solar spectrum is due to the vapour of sodium in the sun’s atmosphere.
2. attrib. a. In the names of chemical compounds or groupings, as sodium-alcohol, -amyl, bicarbonate, bromide, carbonate, etc.
1857. Miller, Elem. Chem., Org., 150. If iodide of amyl be made to act upon the sodium-alcohol. Ibid. (1862), (ed. 2), 222. When sodium-ethyl is formed from zinc-ethyl by the action of sodium. Ibid., 225. Sodium-amyl would probably furnish caproate of soda.
1868. Fownes’ Chem. (ed. 10), 337. Sodium Chloride, when pure, is not deliquescent in moderately-dry air. Ibid. Sodium Hydrate, or Caustic Soda. Ibid., 338. Sodium Carbonates. Ibid., 345. Sodium Hyposulphite … is now used in considerable quantity for photographic purposes.
1873. Ralfe, Phys. Chem., 105. The potassium and sodium phosphates form three varieties of salts.
b. Misc., as sodium-compound, -flame, -light; sodium-amalgam, a compound of mercury and sodium; sodium soap, soda soap.
1862. Miller, Elem. Chem., Org. (ed. 2), 219. The potassium and sodium compounds are more energetic than those of zinc.
1866. W. Odling, Anim. Chem., 138. Uric acid, by deoxidation with sodium-amalgam, yields a mixture of xanthine and hypoxanthine.
1871. Tyndall, Fragm. Sci. (1879), I. xiv. 391. We send our beam of white light through a sodium flame.
1888. Rutley, Rock-Forming Min., 128. The refractive index of quartz … in sodium-light.
