Chemical element of metals. Cu comes from Cuprum, Fe comes from Ferrum, Ag from Argentum. The symbols were not followed by a period (full stop) as with abbreviations. Later chemical elements were also assigned unique chemical symbols, based on the name of the element, but not necessarily in English. For example, sodium has the chemical symbol 'Na' after the Latin "natrium". The same applies to "W" (wolfram) for tungsten, "Fe" (ferrum) for iron, "Hg" (hydrargyrum) for mercury, "Sn" (stannum) for tin, "K" (kalium) for potassium, "Au" (aurum) for gold, "Ag" (argentum) for silver, "Pb" (plumbum) for lead, "Cu" (cuprum) for copper, and
Cobalt(III) hydroxide at –30 to –35°С, then adding a 15% solution of sodium carbonate in water with intense stirring. The resulting dark green powder is fairly stable at liquid nitrogen temperature, but at room temperature it turns dark brown within a few days. Cobalt(III) hydroxide Cobalt(III) hydroxide or cobaltic hydroxide is a chemical compound with formula or . It is an ionic compound, with trivalent cobalt cations and hydroxyl anions . The compound is known in two structurally different forms, "brownish-black" and "green". The brownish-black form is a stable solid and can be prepared by reaction of water solutions of cobalt(II) chloride